Search

Visually guided reaches are performed in ≈1s. Given unstable feedback control with neural transmission delay, stable visually guided reaching is assumed to require internal feedforward models that generate simulated feedback without delay that combines with actual feedback for stability. We investigated whether stable visually guided reaching requires internal models to handle such delay. Participants performed rapid targeted reaches in a virtual environment with different mappings between speeds of the hand and hand avatar. First, participants reached with visual guidance and constant mapping. Second, feedforward reaches were performed with constant mapping and hand avatar only visible at reach start and end. Reaches were accurate. Third, participants performed reaches with visual guidance and different mappings every trial. We expected performance as in the first condition. Finally, feedforward reaches with variable mapping yielded large errors showing visual guidance in the previous condition was successful despite an ineffective internal model. We simulated reaches using a proportional rate model with disparity Tau controlling the virtual Equilibrium Point in an Equilibrium Point (EP) model. The time dimensioned information and dynamic remained stable with delayed feedback. Finally, we fit movement times using the proportional rate EP model with 0msec, 50msec, and 100msec delay. With the fitted model parameters, we compared the model reach trajectories with the behavioral trajectories. Stable visually guided reaching did not require an internal feedforward model., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Reaches guided using monocular versus binocular vision have been found to be equally fast and accurate only when optical texture was available projected from a support surface across which the reach was performed. We now investigate what property of optical texture elements is used to perceive relative distance: image width, image height, or image shape. Participants performed reaches to match target distances. Targets appeared on a textured surface on the left and participants reached to place their hand at target distance along a surface on the right. A perturbation discriminated which texture property was being used. The righthand surface was higher than the lefthand one by either 2, 4 or 6 cm. Participants should overshoot if they matched texture image width at the target, undershoot if they matched image shape, and undershoot far distances and, depending on the overall eye height, overshoot near distances if they matched image height. In Experiment 1, participants reached by moving a joystick to control a hand avatar in a virtual environment display. Their eye height was 15 cm. For each texture property, distances were predicted from the viewing geometry. Results ruled out image width in favor of image height or shape. In Experiment 2, participants at a 50 cm eye height reached in an actual environment with the same manipulations. Results supported use of image shape (or foreshortening), consistent with findings of texture properties used in slant perception. We discuss implications for models of visually guided reaching., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The most widely known studies of rhythmic limb coordination showed that frequency strongly affects the stability of some coordinations (e.g. 180° relative phase) but not others (e.g. 0°). The coupling of such rhythmic limb movements was then shown to be perceptual. Frequency affected the stability of perceptual information. We now investigated whether frequency would impact the pickup of information for learning a novel bimanual coordination pattern (e.g. 90°) and the ability to sustain the coordination at various frequencies. Twenty participants were recruited and assessed on their performance of bimanual coordination at 0°, 180°, and 90° at five scanning frequencies before and after training at 90°, during which they were assigned to practice with either a high (2.5 Hz) or low (0.5 Hz) frequency until attaining proficiency. The results showed that learning was frequency specific. The best post-training performance occurred at the trained frequency. Although the coordination could be acquired through high frequency training, it was at the cost of a greater amount of training and most surprisingly, did not yield improved performance at lower frequencies that are normally thought to be easier. The findings suggest that movement frequency may determine whether visual or kinesthetic information is used for learning and control of bimanual coordination., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Gibson formulated an approach to goal-directed behavior using prospective information in the context of visually guided locomotion and manual behavior. The former was Gibson's paradigm case, but it is the rapidity of targeted reaching that has provided the special challenge for stable control. Recent treatments of visually guided reaching assume that internal forward models are required to generate stable behavior given delays caused by neural transmission times. Internal models are representations of the sort eschewed by Gibson in favor of prospective information. Reaching is usually described as guided using relative distances of hand and target, but prospective information is usually temporal rather than spatial. We describe proportional rate control models that incorporate time dimensioned prospective information and show they remain stable in the face of delays. The use of time-dimensioned prospective information removes the need for internal models for stable behavior despite neural transmission delays and allows Gibson's approach to prevail., Competing Interests: Declaration of Conflicting Interests: The author declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2021.)

Two rhythmic coordinations, 0° and 180° relative phase, can be performed stably at preferred frequency (~ 1 Hz) without training. Evidence indicates that both 0° and 180° coordination entail detection of the relative direction of movement. At higher frequencies, this yields instability of 180° and spontaneous transition to 0°. The ability to perform a 90° coordination can be acquired by learning to detect and use relative position as information. We now investigate the skilled performance of 90° bimanual coordination with frequency scaling and whether 90° coordination exhibits mode switching to 0° or 180° at higher frequencies. Unlike the switching from 180° to 0°, a transition from the learned 90° coordination to the intrinsic 0° or 180° modes would entail a change in information. This would seem to require intentional decisions during performance as would correcting performance that had strayed from 90°. Relatedly, correction would seem to be an intrinsic part of the performance of 90° during learning. We investigated whether it remains so. We tested bimanual coordination at 90° under both noninterference and correcting instructions. Under correcting instructions, bimanual 90° coordination remained stable at both low and high frequencies. Noninterference instructions yielded stable performance at lower frequencies and switching to 0° or 180° at higher frequencies. Thus, correction is optional and switching to the intrinsic modes occurred. We extended the Bingham (Ecol Psychol 16:45-53, 2004a; Advances in psychology, vol. 135, Time-to-contact, Elsevier Science Publishers, 2004b) model for 0° and 180° coordination to create a dynamical, perception-action account of learned 90° bimanual coordination, in which mode switching and correction were both initiated as the information required for performance of 90° fell below threshold. This means that intentional decisions about what coordination to perform and whether to correct occurred only before performance was begun, not during performance. The extended strictly dynamical model was successfully used to simulate performance of participants in the experiments., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Two groups of participants were trained to be proficient at performing bimanual 90° coordination either at a high (2.5 Hz) or low (0.5 Hz) frequency with both kinesthetic and visual information available. At high frequency, participants trained for twice as long to achieve performance comparable to participants training at low frequency. Participants were then paired within (low-low or high-high) or between (low-high) frequency groups to perform a visually coupled dyadic unimanual 90° coordination task, during which they were free to settle at any jointly determined frequency to synchronize their rhythmic movements. The results showed that the coordination skill was frequency-specific. For dyads with one or both members who had learned the 90° bimanual coordination at low frequency, the performance settled at a low frequency (≈0.5 Hz) with more successfully synchronized trials. For dyads with both members who had learned the 90° bimanual coordination at high frequency, they struggled with the task and performed poorly. The dyadic coordination settled at a higher frequency (≈1.5 Hz) on average, but with twice the variability in settling frequency and significantly fewer synchronized trials. The difference between the dyadic coordination and bimanual tasks was that only visual information was available to couple the movements in the former while both kinesthetic and visual information were available in the latter. Therefore, the high frequency group must have relied on kinesthetic information to perform both coordination tasks while the low frequency group was well able to use visual information for both. In the mixed training pairs, the low frequency trained member of the pair was likely responsible for the better performance. These conclusions were consistent with results of previous studies., (Copyright © 2021 Elsevier B.V. All rights reserved.)

We investigated monocular information for the continuous online guidance of reaches-to-grasp and present a dynamical control model thereof. We defined an information variable using optical texture projected from a support surface (i.e. a table) over which the participants reached-to-grasp target objects sitting on the table surface at different distances. Using either binocular or monocular vision in the dark, participants rapidly reached-to-grasp a phosphorescent square target object with visibly phosphorescent thumb and index finger. Targets were one of three sizes. The target either sat flat on the support surface or was suspended a few centimeters above the surface at a slant. The later condition perturbed the visible relation of the target to the support surface. The support surface was either invisible in the dark or covered with a visible phosphorescent checkerboard texture. Reach-to-grasp trajectories were recorded and Maximum Grasp Apertures (MGA), Movement Times (MT), Time of MGA (TMGA), and Time of Peak Velocities (TPV) were analyzed. These measures were selected as most indicative of the participant's certainty about the relation of hand to target object during the reaches. The findings were that, in general, especially monocular reaches were less certain (slower, earlier TMGA and TPV) than binocular reaches except with the target flat on the visible support surface where performance with monocular and binocular vision was equivalent. The hypothesized information was the difference in image width of optical texture (equivalent to density of optical texture) at the hand versus the target. A control dynamic equation was formulated representing proportional rate control of the reaches-to-grasp (akin to the model using binocular disparity formulated by Anderson and Bingham (Exp Brain Res 205: 291-306, 2010). Simulations were performed and presented using this model. Simulated performance was compared to actual performance and found to replicate it. To our knowledge, this is the first study of monocular information used for continuous online guidance of reaches-to-grasp, complete with a control dynamic model.

Information used in visual event perception includes both static image structure projected from opaque object surfaces and dynamic optic flow generated by motion. Events presented in static blurry grayscale displays have been shown to be recognized only when and after presented with optic flow. In this study, we investigate the effects of optic flow and color on identifying blurry events by studying the identification accuracy and eye-movement patterns. Three types of color displays were tested: grayscale, original colors, or rearranged colors (where the RGB values of the original colors were adjusted). In each color condition, participants identified 12 blurry events in five experimental phases. In the first two phases, static blurry images were presented alone or sequentially with a motion mask between consecutive frames, and identification was poor. In Phase 3, where optic flow was added, identification was comparably good. In Phases 4 and 5, motion was removed, but identification remained good. Thus, optic flow improved event identification during and after its presentation. Color also improved performance, where participants were consistently better at identifying color displays than grayscale or rearranged color displays. Importantly, the effects of optic flow and color were additive. Finally, in both motion and postmotion phases, a significant portion of eye fixations fell in strong optic flow areas, suggesting that participants continued to look where flow was available even after it stopped. We infer that optic flow specified depth structure in the blurry image structure and yielded an improvement in identification from static blurry images.

This study investigated the optical information and control strategies used in visually guided braking. In such tasks, drivers exhibit two different braking behaviors: impulsive braking and continuously regulated braking. We designed two experiments involving a simulated braking task to investigate these two behaviors. Participants viewed computer displays simulating an approach along a linear path over a textured ground surface toward a set of road signs. The task was to use a joystick as a brake to stop as close as possible to the road signs. Our results showed that participants relied on a weak constant-[Formula: see text] strategy (Bingham 1995) when regulating the brake impulsively. They used discrete [Formula: see text] values as critical values and they regulated the brake so as not to let [Formula: see text] fall below these values. Our results also showed that proportional rate control (Anderson and Bingham 2010, 2011) is used in continuously regulated braking. Participants initiated braking at a certain proportional rate value and controlled braking so as to maintain that value constant during the approach. Proportional rate control is robust because the value can fluctuate within a range to yield good performance. We argue that proportional rate control unifies the information-based approach and affordance-based approach to visually guided braking.

Previously, we developed a stratified process for slant perception. First, optical transformations in structure-from-motion (SFM) and stereo were used to derive 3D relief structure (where depth scaling remains arbitrary). Second, with sufficient continuous perspective change (≥45°), a bootstrap process derived 3D similarity structure. Third, the perceived slant was derived. As predicted by theoretical work on SFM, small visual angle (<5°) viewing requires non-coplanar points. Slanted surfaces with small 3D cuboids or tetrahedrons yielded accurate judgment while planar surfaces did not. Normally, object perception entails non-coplanar points. Now, we apply the stratified process to object perception where, after deriving similarity structure, alternative metric properties of the object can be derived (e.g. slant of the top surface or width-to-depth aspect ratio). First, we tested slant judgments of the smooth planar tops of three different polyhedral objects. We tested rectangular, hexagonal, and asymmetric pentagonal surfaces, finding that symmetry was required to determine the direction of slant (AP&P, 2019, https://doi.org/10.3758/s13414-019-01859-5). Our current results replicated the previous findings. Second, we tested judgments of aspect ratios, finding accurate performance only for symmetric objects. Results from this study suggest that, first, trackable non-coplanar points can be attained in the form of 3D objects. Second, symmetry is necessary to constrain slant and aspect ratio perception. Finally, deriving 3D similarity structure precedes estimating object properties, such as slant or aspect ratio. Together, evidence presented here supports the stratified bootstrap process for 3D object perception. STATEMENT OF SIGNIFICANCE: Planning interactions with objects in the surrounding environment entails the perception of 3D shape and slant. Studying ways through which 3D metric shape and slant can be perceived accurately by moving observers not only sheds light on how the visual system works, but also provides understanding that can be applied to other fields, like machine vision or remote sensing. The current study is a logical extension of previous studies by the same authors and explores the roles of large continuous perspective changes, relief structure, and symmetry in a stratified process for object perception., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Empirical studies have always shown 3-D slant and shape perception to be inaccurate as a result of relief scaling (an unknown scaling along the depth direction). Wang, Lind, and Bingham (Journal of Experimental Psychology: Human Perception and Performance, 44(10), 1508-1522, 2018) discovered that sufficient relative motion between the observer and 3-D objects in the form of continuous perspective change (≥45°) could enable accurate 3-D slant perception. They attributed this to a bootstrap process (Lind, Lee, Mazanowski, Kountouriotis, & Bingham in Journal of Experimental Psychology: Human Perception and Performance, 40(1), 83, 2014) where the perceiver identifies right angles formed by texture elements and tracks them in the 3-D relief structure through rotation to extrapolate the unknown scaling factor, then used to convert 3-D relief structure to 3-D Euclidean structure. This study examined the nature of the bootstrap process in slant perception. In a series of four experiments, we demonstrated that (1) features of 3-D relief structure, instead of 2-D texture elements, were tracked (Experiment 1); (2) identifying right angles was not necessary, and a different implementation of the bootstrap process is more suitable for 3-D slant perception (Experiment 2); and (3) mirror symmetry is necessary to produce accurate slant estimation using the bootstrapped scaling factor (Experiments 3 and 4). Together, the results support the hypothesis that a symmetry axis is used to determine the direction of slant and that 3-D relief structure is tracked over sufficiently large perspective change to produce metric depth. Altogether, the results supported the bootstrap process.

Lind et al. (Journal of Experimental Psychology: Human Perception and Performance, 40 (1), 83, 2014) proposed a bootstrap process that used right angles on 3D relief structure, viewed over sufficiently large continuous perspective change, to recover the scaling factor for metric shape. Wang, Lind, and Bingham (Journal of Experimental Psychology: Human Perception and Performance, 44(10), 1508-1522, 2018) replicated these results in the case of 3D slant perception. However, subsequent work by the same authors (Wang et al., 2019) suggested that the original solution could be ineffective for 3D slant and presented an alternative that used two equidistant points (a portion of the original right angle). We now describe a three-step stratified process to recover 3D slant using this new solution. Starting with 2D inputs, we (1) used an existing structure-from-motion (SFM) algorithm to derive the object's 3D relief structure and (2) applied the bootstrap process to it to recover the unknown scaling factor, which (3) was then used to produce a slant estimate. We presented simulations of results from four previous experiments (Wang et al., 2018, 2019) to compare model and human performance. We showed that the stratified process has great predictive power, reproducing a surprising number of phenomena found in human experiments. The modeling results also confirmed arguments made in Wang et al. (2019) that an axis of mirror symmetry in an object allows observers to use the recovered scaling factor to produce an accurate slant estimate. Thus, poor estimates in the context of a lack of symmetry do not mean that the scaling factor has not been recovered, but merely that the direction of slant was ambiguous.

A large proportion of school-aged children exhibit poor drawing and handwriting. This prevalence limits the availability of therapy. We developed an automated method for training improved manual compliance control and relatedly, prospective control of a stylus. The approach included a difficult training task, while providing parametrically modifiable support that enables the children to perform successfully while developing good compliance control. The task was to use a stylus to push a bead along a 3D wire path. Support was provided by making the wire magnetically attractive to the stylus. Support was progressively reduced as 3D tracing performance improved. We report studies that (1) compared performance of Typically Developing (TD) children and children with Developmental Coordination Disorder (DCD), (2) tested training with active versus passive movement, (3) tested progressively reduced versus constant or no support during training, (4) tested children of different ages, (5) tested the transfer of training to a drawing task, (6) tested the specificity of training in respect to the size, shape and dimensionality of figures, and (7) investigated the relevance of the training task to the Beery VMI, an inventory used to diagnose DCD. The findings were as follows. (1) Pre-training performance of TD and DCD children was the same and good with high support but distinct and poor with low support. Support yielded good self-efficacy that motivated training. Post training performance with no support was improved and the same for TD and DCD children. (2) Actively controlled movements were required for improved performance. (3) Progressively reduced support was required for good performance during and after training. (4) Age differences in performance during pre-training were eliminated post-training. (5) Improvements transferred to drawing. (6) There was no evidence of specificity of training in transfer. (7) Disparate Beery scores were reflected in pre-training but not post-training performance. We conclude that the method improves manual compliance control, and more generally, prospective control of movements used in drawing performance., (Copyright © 2018. Published by Elsevier B.V.)

Mon-Williams and Bingham (Exp Brain Res 211(1):145-160, 2011) developed a geometrical affordance model for reaches-to-grasp, and identified a constant scaling relationship, P, between safety margins (SM) and available apertures (SM) that are determined by the sizes of the objects and the individual hands. Bingham et al. (J Exp Psychol Hum Percept Perform 40(4):1542-1550, 2014) extended the model by introducing a dynamical component that scales the geometrical relationship to the stability of the reaching-to-grasp. The goal of the current study was to explore whether and how quickly change in the relevant effectivity (functionally determined hand size = maximum grip) would affect the geometrical and dynamical scaling relationships. The maximum grip of large-handed males was progressively restricted. Participants responded to this restriction by using progressively smaller safety margins, but progressively larger P (= SM/AA) values that preserved an invariant dynamical scaling relationship. The recalibration was relatively fast, occurring over five trials or less, presumably a number required to detect the variability or stability of performance. The results supported the affordance model for reaches-to-grasp in which the invariance is determined by the dynamical component, because it serves the goal of not colliding with the object before successful grasping can be achieved. The findings were also consistent with those of Snapp-Childs and Bingham (Exp Brain Res 198(4):527-533, 2009) who found changes in age-specific geometric scaling for stepping affordances as a function of changes in effectivities over the life span where those changes preserved a dynamic scaling constant similar to that in the current study.

Perceived slant has often been characterized as a component of 3D shape perception for polyhedral objects. Like 3D shape, slant is often perceived inaccurately. Lind, Lee, Mazanowski, Kountouriotis, and Bingham (2014) found that 3D shape was perceived accurately with perspective changes ≥ 45°. We now similarly tested perception of 3D slant. To account for their results, Lind et al. (2014) developed a bootstrap model based on the assumption that optical information yields perception of 3D relief structure then used with large perspective changes to bootstrap to perception of 3D Euclidean structure. However, slant perception usually entails planar surfaces and structure-from-motion fails in the absence of noncoplanar points. Nevertheless, the displays in Lind et al. (2014) included stereomotion in addition to monocular optical flow. Because stereomotion is higher order, the bootstrap model might apply in the case of strictly planar surfaces. We investigated whether stereomotion, monocular structure-from-motion (SFM), or the combination of the two would yield accurate 3D slant perception with large continuous perspective change. In Experiment 1, we found that judgments of slant were inaccurate in all information conditions. In Experiment 2, we added noncoplanar structure to the surfaces. We found that judgments in the monocular SFM and combined conditions now became correct once perspective changes were ≥ 45°, replicating the results of Lind et al. (2014) and supporting the bootstrap model. In short, we found that noncoplanar structure was required to enable accurate perception of 3D slant with sufficiently large perspective changes. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Previously we developed a method that supports active movement generation to allow practice with improvement of good compliance control in tracing and drawing. We showed that the method allowed children with motor impairments to improve at a 3D tracing task to become as proficient as typically developing children and that the training improved 2D figure copying. In this study, we expanded the training protocol to include a wider variety of ages (5-10-year-olds) and we made the figures traced in training the same as in figure copying, but varied the scale of training and copying figures to assess the generality of learning. Forty-eight children were assigned to groups trained using large or small figures. All were tested before training with a tracing task and a copying task. Then, the children trained over five sessions in the tracing task with either small or large figures. Finally, the tracing and copying tasks were tested again following training. A mean speed measure was used to control for path length variations in the timed task. Performance on both tasks at both baseline and posttest varied as a function of the size of the figure and age. In addition, tracing performance also varied with the level of support. In particular, speeds were higher with more support, larger figures and older children. After training, performance improved. Speeds increased. In tracing, performance improved more for large figures traced by children who trained on large figures. In copying, however, performance only improved significantly for children who had trained on small figures and it improved equally for large and small figures. In conclusion, training by tracing smaller figures yielded better learning that was not, however, specific to the scale of drawn figures. Small figures exhibit greater mean curvature. We infer that it yielded better general improvement.

When we move through rigid environments, surface orientations of static objects do not appear to change. Most studies have investigated the perception of optical slant which is dependent on the perspective of the observer. We investigated the perception of geographical slant, which is invariant across different viewing perspectives, and compared it to optical slant. In Experiment 1, participants viewed a 3D triangular target surface with triangular phosphorescent texture elements presented at eye level at one of 5 slants from 0° to 90°, at 0° or 40° tilt. Participants turned around to adjust a 2D line or a 3D surface to match the slant of the target surface. In Experiment 2, the difference between optical and geographical slant was increased by changing the height of the surface to be judged. In Experiment 3, target surfaces were rotated by 50° (±25°) and viewed in both a dark and lighted room. In Experiment 1, the overall pattern of judgments exhibited only slight differences between response measures. In Experiment 2, slant judgments were slightly overestimated when the surface was at a low height and at 0° tilt. We compared optical slants of the surfaces to geographical slants. While sometimes inaccurate, participants' slant judgments remained invariant across changes in viewing perspective. In Experiment 3, judgments were the same in the dark and lighted conditions. There was no effect of target motion on judgments, although variability decreased. We conclude that participants' judgments were predicted by geographical slant, not optical slant., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

How is information from different sensory modalities coordinated when learning an action? We tested two hypotheses. The first is that the information is amodal. The second is that the information is modality specific and one modality is used in first learning the action and then is used to teach the other modality. We investigated these hypotheses using a rhythmic coordination task. One group of participants learned to perform bimanual coordination at a relative phase of 90° using kinesthesis. A second group used vision to learn unimanual 90° coordination. After training, performance using the alternate modality was tested in each case. Snapp-Childs, Wilson, and Bingham (2015) had found transfer of 50% of learned performance of 90° coordination between the unimanual and bimanual tasks when each had included use of vision. Now, we found essentially no transfer (≈5%) indicating that the information was modality specific. Next, post-training trials performed using the untrained modality were alternated with trials in which kinesthesis and vision were used. The result was that performance using the untrained modality progressively improved. We concluded that trained modality was used to teach the untrained modality and that this likely represents the way information from different sensory modalities is coordinated in performance of actions., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The role of the monocular-flow-based optical variable τ in the perception of the time to contact of approaching objects has been well-studied. There are additional contributions from binocular sources of information, such as changes in disparity over time (CDOT), but these are less understood. We conducted an experiment to determine whether an object's velocity affects which source is most effective for perceiving time to contact. We presented participants with stimuli that simulated two approaching squares. During approach the squares disappeared, and participants indicated which square would have contacted them first. Approach was specified by (a) only disparity-based information, (b) only monocular flow, or (c) all sources of information in normal viewing conditions. As expected, participants were more accurate at judging fast objects when only monocular flow was available than when only CDOT was. In contrast, participants were more accurate judging slow objects with only CDOT than with only monocular flow. For both ranges of velocity, the condition with both information sources yielded performance equivalent to the better of the single-source conditions. These results show that different sources of motion information are used to perceive time to contact and play different roles in allowing for stable perception across a variety of conditions.

Events consist of objects in motion. When objects move, their opaque surfaces reflect light and produce both static image structure and dynamic optic flow. The static and dynamic optical information co-specify events. Patients with age-related macular degeneration (AMD) and amblyopia cannot identify static objects because of weakened image structure. However, optic flow is detectable despite blurry vision because visual motion measurement uses low spatial frequencies. When motion ceases, image structure persists and might preserve properties specified by optic flow. We tested whether optic flow and image structure interact to allow event perception with poor static vision. AMD (Experiment 1), amblyopic (Experiments 2 and 3), and normally sighted observers identified common events from either blurry (Experiments 1 and 2) or clear images (Experiment 3), when either single image frames were presented, a sequence of frames was presented with motion masks, or a sequence of frames was presented with detectable motion. Results showed that with static images, but no motion, events were not perceived well by participants other than controls in Experiment 3. However, with detectable motion, events were perceived. Immediately following this and again after five days, participants were able to identify events from the original static images. So, when image structure information is weak, optic flow compensates for it and enables event perception. Furthermore, weakened static image structure information nevertheless preserves information that was once available in optic flow. The combination is powerful and allows events to be perceived accurately and stably despite blurry vision.

Many studies have shown that rhythmic interlimb coordination involves perception of the coupled limb movements, and different sensory modalities can be used. Using visual displays to inform the coupled bimanual movement, novel bimanual coordination patterns can be learned with practice. A recent study showed that similar learning occurred without vision when a coach provided manual guidance during practice. The information provided via the two different modalities may be same (amodal) or different (modality specific). If it is different, then learning with both is a dual task, and one source of information might be used in preference to the other in performing the task when both are available. In the current study, participants learned a novel 90° bimanual coordination pattern without or with visual information in addition to kinesthesis. In posttest, all participants were tested without and with visual information in addition to kinesthesis. When tested with visual information, all participants exhibited performance that was significantly improved by practice. When tested without visual information, participants who practiced using only kinesthetic information showed improvement, but those who practiced with visual information in addition showed remarkably less improvement. The results indicate that (1) the information is not amodal, (2) use of a single type of information was preferred, and (3) the preferred information was visual. We also hypothesized that older participants might be more likely to acquire dual task performance given their greater experience of the two sensory modes in combination, but results were replicated with both 20- and 50-year-olds.

Use of motion to break camouflage extends back to the Cambrian [In the Blink of an Eye: How Vision Sparked the Big Bang of Evolution (New York Basic Books, 2003)]. We investigated the ability to break camouflage and continue to see camouflaged targets after motion stops. This is crucial for the survival of hunting predators. With camouflage, visual targets and distracters cannot be distinguished using only static image structure (i.e., appearance). Motion generates another source of optical information, optic flow, which breaks camouflage and specifies target locations. Optic flow calibrates image structure with respect to spatial relations among targets and distracters, and calibrated image structure makes previously camouflaged targets perceptible in a temporally stable fashion after motion stops. We investigated this proposal using laboratory experiments and compared how many camouflaged targets were identified either with optic flow information alone or with combined optic flow and image structure information. Our results show that the combination of motion-generated optic flow and target-projected image structure information yielded efficient and stable perception of camouflaged targets.

Rotating a scene in a frontoparallel plane (rolling) yields a change in orientation of constituent images. When using only information provided by static images to perceive a scene after orientation change, identification performance typically decreases (Rock & Heimer, 1957). However, rolling generates optic flow information that relates the discrete, static images (before and after the change) and forms an embodied memory that aids recognition. The embodied memory hypothesis predicts that upon detecting a continuous spatial transformation of image structure, or in other words, seeing the continuous rolling process and objects undergoing rolling observers should accurately perceive objects during and after motion. Thus, in this case, orientation change should not affect performance. We tested this hypothesis in three experiments and found that (a) using combined optic flow and image structure, participants identified locations of previously perceived but currently occluded targets with great accuracy and stability (Experiment 1); (b) using combined optic flow and image structure information, participants identified hidden targets equally well with or without 30° orientation changes (Experiment 2); and (c) when the rolling was unseen, identification of hidden targets after orientation change became worse (Experiment 3). Furthermore, when rolling was unseen, although target identification was better when participants were told about the orientation change than when they were not told, performance was still worse than when there was no orientation change. Therefore, combined optic flow and image structure information, not mere knowledge about the rolling, enables accurate and stable perception despite orientation change. (PsycINFO Database Record, ((c) 2017 APA, all rights reserved).)

Spheroids are ball-shaped stone objects found in African archaeological sites dating from 1.8 million years ago (Early Stone Age) to at least 70,000 years ago (Middle Stone Age). Spheroids are either fabricated or naturally shaped stones selected and transported to places of use making them one of the longest-used technologies on record. Most hypotheses about their use suggest they were percussive tools for shaping or grinding other materials. However, their size and spherical shape make them potentially useful as projectile weapons, a property that, uniquely, humans have been specialised to exploit for millions of years. Here we show (using simulations of projectile motions resulting from human throwing) that 81% of a sample of spheroids from the late Acheulean (Bed 3) at the Cave of Hearths, South Africa afford being thrown so as to inflict worthwhile damage to a medium-sized animal over distances up to 25 m. Most of the objects have weights that produce optimal levels of damage from throwing, rather than simply being as heavy as possible (as would suit other functions). Our results show that these objects were eminently suitable for throwing, and demonstrate how empirical research on behavioural tasks can inform and constrain our theories about prehistoric artefacts.

There are a large number of children with motor difficulties including those that have difficulty producing movements qualitatively well enough to improve in perceptuo-motor learning without intervention. We have developed a training method that supports active movement generation to allow improvement in a 3D tracing task requiring good compliance control. Previously, we tested a limited age range of children and found that training improved performance on the 3D tracing task and that the training transferred to a 2D drawing test. In the present study, school children (5-11years old) with motor difficulties were trained in the 3D tracing task and transfer to a 2D drawing task was tested. We used a cross-over design where half of the children received training on the 3D tracing task during the first training period and the other half of the children received training during the second training period. Given previous results, we predicted that younger children would initially show reduced performance relative to the older children, and that performance at all ages would improve with training. We also predicted that training would transfer to the 2D drawing task. However, the pre-training performance of both younger and older children was equally poor. Nevertheless, post-training performance on the 3D task was dramatically improved for both age groups and the training transferred to the 2D drawing task. Overall, this work contributes to a growing body of literature that demonstrates relatively preserved motor learning in children with motor difficulties and further demonstrates the importance of games in therapeutic interventions., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In 2 experiments, the current study explored how affordances structure throwing for long distance and accuracy. In Experiment 1, 10 expert throwers (from baseball, softball, and cricket) threw regulation tennis balls to hit a vertically oriented 4 ft × 4 ft target placed at each of 9 locations (3 distances × 3 heights). We measured their release parameters (angle, speed, and height) and showed that they scaled their throws in response to changes in the target's location. We then simulated the projectile motion of the ball and identified a continuous subspace of release parameters that produce hits to each target location. Each subspace describes the affordance of our target to be hit by a tennis ball moving in a projectile motion to the relevant location. The simulated affordance spaces showed how the release parameter combinations required for hits changed with changes in the target location. The experts tracked these changes in their performance and were successful in hitting the targets. We next tested unusual (horizontal) targets that generated correspondingly different affordance subspaces to determine whether the experts would track the affordance to generate successful hits. Do the experts perceive the affordance? They do. In Experiment 2, 5 cricketers threw to hit either vertically or horizontally oriented targets and successfully hit both, exhibiting release parameters located within the requisite affordance subspaces. We advocate a task dynamical approach to the study of affordances as properties of objects and events in the context of tasks as the future of research in this area. (PsycINFO Database Record, ((c) 2016 APA, all rights reserved).)

Zannoli, Cass, Alais, and Mamassian (2012) found greater audiovisual lag between a tone and disparity-defined stimuli moving laterally (90-170 ms) than for disparity-defined stimuli moving in depth or luminance-defined stimuli moving laterally or in depth (50-60 ms). We tested if this increased lag presents an impediment to visually guided coordination with laterally moving objects. Participants used a joystick to move a virtual object in several constant relative phases with a laterally oscillating stimulus. Both the participant-controlled object and the target object were presented using a disparity-defined display that yielded information through changes in disparity over time (CDOT) or using a luminance-defined display that additionally provided information through monocular motion and interocular velocity differences (IOVD). Performance was comparable for both disparity-defined and luminance-defined displays in all relative phases. This suggests that, despite lag, perception of lateral motion through CDOT is generally sufficient to guide coordinated motor behavior.

Motor deficits are linked to a range of negative physical, social and academic consequences. Haptic robotic interventions, based on the principles of sensorimotor learning, have been shown previously to help children with motor problems learn new movements. We therefore examined whether the training benefits of a robotic system would generalise to a standardised test of 'pen-skills', assessed using objective kinematic measures [via the Clinical Kinematic Assessment Tool, CKAT]. A counterbalanced, cross-over design was used in a group of 51 children (37 male, aged 5-11 years) with manual control difficulties. Improved performance on a novel task using the robotic device could be attributed to the intervention but there was no evidence of generalisation to any of the CKAT tasks. The robotic system appears to have the potential to support motor learning, with the technology affording numerous advantages. However, the training regime may need to target particular manual skills (e.g. letter formation) in order to obtain clinically significant improvements in specific skills such as handwriting.

Previous empirical and theoretical work suggests that effective skill acquisition requires movements to be generated actively and that learning new skills supports the acquisition of prospective control. However, there are many ways in which practice can be structured, that may affect the acquisition and use of prospective control after training. Here, we tested whether the progressive modulation and reduction of support during training was required to yield good performance after training without support. The task was to use a stylus to push a bead over a complex 3D wire path. The support "magnetically" attracted and held the stylus onto the wire. Three groups of adult participants each experienced one of three training regimes: gradual reduction of magnetic attraction, only a medium level of attraction, or low magnetic attraction. The results showed that use of a single (medium) level of support was significantly less effective in yielding good performance with low support after training. Training with low support yielded post-training performance that was equally good as that yielded by training with progressive reduction of support; however, performance during training was significantly poorer in the former. Thus, less support during training yields effective learning but more difficult training sessions. The results are discussed in the context of application to training with special populations., (Copyright © 2015. Published by Elsevier B.V.)

Many children have difficulty producing movements well enough to improve in perceptuo-motor learning. We have developed a training method that supports active movement generation to allow improvement in a 3D tracing task requiring good compliance control. We previously tested 7-8 year old children who exhibited poor performance and performance differences before training. After training, performance was significantly improved and performance differences were eliminated. According to the Dynamic Systems Theory of development, appropriate support can enable younger children to acquire the ability to perform like older children. In the present study, we compared 7-8 and 10-12 year old school children and predicted that younger children would show reduced performance that was nonetheless amenable to training. Indeed, the pre-training performance of the 7-8 year olds was worse than that of the 10-12 year olds, but post-training performance was equally good for both groups. This was similar to previous results found using this training method for children with DCD and age-matched typically developing children. We also found in a previous study of 7-8 year old school children that training in the 3D tracing task transferred to a 2D drawing task. We now found similar transfer for the 10-12 year olds., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Under certain conditions, learning can transfer from a trained task to an untrained version of that same task. However, it is as yet unclear what those certain conditions are or why learning transfers when it does. Coordinated rhythmic movement is a valuable model system for investigating transfer because we have a model of the underlying task dynamic that includes perceptual coupling between the limbs being coordinated. The model predicts that (1) coordinated rhythmic movements, both bimanual and unimanual, are organised with respect to relative motion information for relative phase in the coupling function, (2) unimanual is less stable than bimanual coordination because the coupling is unidirectional rather than bidirectional, and (3) learning a new coordination is primarily about learning to perceive and use the relevant information which, with equal perceptual improvement due to training, yields equal transfer of learning from bimanual to unimanual coordination and vice versa [but, given prediction (2), the resulting performance is also conditioned by the intrinsic stability of each task]. In the present study, two groups were trained to produce 90° either unimanually or bimanually, respectively, and tested in respect to learning (namely improved performance in the trained 90° coordination task and improved visual discrimination of 90°) and transfer of learning (to the other, untrained 90° coordination task). Both groups improved in the task condition in which they were trained and in their ability to visually discriminate 90°, and this learning transferred to the untrained condition. When scaled by the relative intrinsic stability of each task, transfer levels were found to be equal. The results are discussed in the context of the perception-action approach to learning and performance.

Previously, we measured perceptuo-motor learning rates across the lifespan and found a sudden drop in learning rates between ages 50 and 60, called the "50s cliff." The task was a unimanual visual rhythmic coordination task in which participants used a joystick to oscillate one dot in a display in coordination with another dot oscillated by a computer. Participants learned to produce a coordination with a 90° relative phase relation between the dots. Learning rates for participants over 60 were half those of younger participants. Given existing evidence for visual motion perception deficits in people over 60 and the role of visual motion perception in the coordination task, it remained unclear whether the 50s cliff reflected onset of this deficit or a genuine decline in perceptuo-motor learning. The current work addressed this question. Two groups of 12 participants in each of four age ranges (20s, 50s, 60s, 70s) learned to perform a bimanual coordination of 90° relative phase. One group trained with only haptic information and the other group with both haptic and visual information about relative phase. Both groups were tested in both information conditions at baseline and post-test. If the 50s cliff was caused by an age dependent deficit in visual motion perception, then older participants in the visual group should have exhibited less learning than those in the haptic group, which should not exhibit the 50s cliff, and older participants in both groups should have performed less well when tested with visual information. Neither of these expectations was confirmed by the results, so we concluded that the 50s cliff reflects a genuine decline in perceptuo-motor learning with aging, not the onset of a deficit in visual motion perception.

Locomoting-to-reach to a target is a common visuomotor approach behavior that consists of two nested component actions: locomotion and reaching. The information and control strategies that guide locomotion and reaching in isolation are well studied, but their interaction during locomoting-to-reach behavior has received little attention. We investigated the role of proportional rate control in unifying these components into one action. Individuals use this control strategy with hand-centric disparity-based τ information to guide seated reaching (Anderson and Bingham in Exp Brain Res 205:291-306. doi: 10.1007/s00221-010-2361-9 , 2010) and use it with sequential information to perform targeted locomotion to bring an outstretched arm and hand to a target; first with eye-centric τ information and then hand-centric τ information near the target (Anderson and Bingham in Exp Brain Res 214:631-644. doi: 10.1007/s00221-011-2865-y , 2011). In the current study, participants performed two tasks: locomoting to bring a rigidly outstretched arm and hand to a target (handout), and locomoting to initiate and guide a reach to a target (locomoting-to-reach). Movement trajectories were analyzed. Results show that participants used proportional rate control throughout both tasks, in the sequential manner that was found by Anderson and Bingham (Exp Brain Res 214:631-644. doi: 10.1007/s00221-011-2865-y , 2011). Individual differences were found in the moment at which this information switch occurred in the locomoting-to-reach task. Some participants appeared to switch to proportional rate control with hand-τ once the hand came into view and others switched once the reaching component was complete and the arm was fully outstretched. In the locomoting-to-reach task, participants consistently initiated reaches when eye-τ specified a time-to-contact of 1.0 s. Proportional rate control provides a solution to the degrees-of-freedom problem in the classic manner, by making multiple things one.

Mon-Williams and Bingham (2011) developed an affordance model of the spatial structure of reaches-to-grasp. With a single free parameter (P), the model predicted the safety margins (SMs) exhibited in maximum grasp apertures (MGAs), during the approach of a hand to a target object, as a function of an affordance measure of object size and a functional measure of hand size. An affordance analysis revealed that object size is determined by a diagonal through the object, called the maximum object extent. Mon-Williams and Bingham provided no theoretical account for the empirically determined values of P. We now address this question. Snapp-Childs and Bingham (2009) augmented Warren's (1984) geometric affordance scaling model with a dynamical component determined by the stability of the motor performance. Because P was found to vary with the speeds of reaches, we incorporated a measure of the variability of performance into the model to yield predictions of P. We also found that P varied with gender. In respect to the size of safety margins, women were more conservative in taking risks then men. Finally, following Warren (1984), the classic paradigm for testing affordance models is to test the scaling relations with both small and large participants. We tested small- and large-handed men and small- and large-handed women and found that the new parameter free model successfully accounted for the spatial structure of reaches-to-grasp.

Many children have difficulty producing movements well enough to improve in sensori-motor learning. Previously, we developed a training method that supports active movement generation to allow improvement at a 3D tracing task requiring good compliance control. Here, we tested 7-8 year old children from several 2nd grade classrooms to determine whether 3D tracing performance could be predicted using the Beery VMI. We also examined whether 3D tracing training lead to improvements in drawing. Baseline testing included Beery, a drawing task on a tablet computer, and 3D tracing. We found that baseline performance in 3D tracing and drawing co-varied with the visual perception (VP) component of the Beery. Differences in 3D tracing between children scoring low versus high on the Beery VP replicated differences previously found between children with and without motor impairments, as did post-training performance that eliminated these differences. Drawing improved as a result of training in the 3D tracing task. The training method improved drawing and reduced differences predicted by Beery scores.

Bingham and Pagano (1998) argued that calibration is an intrinsic component of perception-action that yields accurate targeted actions. They described calibration as of a mapping from embodied units of perception to embodied units of action. This mapping theory yields a number of predictions. The authors tested 2 of them. The 1st prediction is that change in the size of perceptual units should yield a corresponding change in the slope of the relation between response distances and actual target distances. In Experiment 1, the authors tested this prediction by manipulating interpupillary distance (IPD) as the unit for binocular perception of distance using vergence angles. In Experiment 2, they manipulated eye height (EH) as the unit for monocular perception of distance using elevation angles. In both cases, the results confirmed the predictions. The 2nd prediction was that perceptual units should interact to cross calibrate one another according to a dominance hierarchy among the units. The theory predicts a more temporally stable unit is used to calibrate a less stable unit but not the reverse. EH units change frequently, but IPD units do not, so IPD should be dominant. Simultaneously available IPD and EH units were perturbed successively (without feedback). As predicted, EH was recalibrated by IPD, but IPD was not recalibrated by EH. The mapping among units theory of calibration was thus supported., (PsycINFO Database Record (c) 2014 APA, all rights reserved.)

Bingham et al. (J Exp Psychol Hum Percept Perform 15(3):507-528, 1989) showed that skilled throwers can perceive optimal objects for throwing to a maximum distance. Zhu and Bingham (J Exp Psychol Hum Percept Perform 34(4):929, 2008, 36(4):862-875, 2010) replicated this finding and then showed that felt heaviness is used to perceive this affordance (see also Zhu and Bingham in Evol Hum Behav 32(4):288-293, 2011; Zhu et al. in Exp Brain Res 224(2):221-231, 2013). Throwers pick the best weight for spherical projectiles in each graspable size. Bingham et al. (J Exp Psychol Hum Percept Perform 15(3):507-528, 1989) speculated that relative throw-ability might be perceptible. This would mean that the ordering of distances achieved by maximum effort throws of different objects could be judged. This affordance property is not the same as optimal throw-ability, because it requires all projectiles to be evaluated relative to one another with respect to ordinally scaled distances, not just a discrete optimum. We now used a magnitude estimation task to test this hypothesis, comparing the resultant ordering with that exhibited by distances of throws in previous studies. The findings show that participants were able to perform the perceptual task. However, discrimination among objects of different weight within a size was better than between sizes. The implications of these results for understanding of the information used to perform this task are discussed.

G. P. Bingham and C. C. Pagano (1998, The necessity of a perception/action approach to definite distance perception: Monocular distance perception to guide reaching. Journal of Experimental Psychology: Human Perception and Performance, 24, 145-168) argued that metric space perception should be investigated using relevant action measures because calibration is an intrinsic component of perception/action that yields accurate targeted actions. They described calibration as a mapping from embodied units of perception to embodied units of action. This mapping theory yields a number of predictions. We tested two of them. The first prediction is that calibration should be action specific because what is calibrated is a mapping from perceptual units to a unit of action. Thus, calibration does not generalize to other actions. This prediction is consistent with the "action-specific approach" to calibration (D. R. Proffitt, 2008, An action specific approach to spatial perception. In R. L. Klatzky, B. MacWhinney, & M. Behrmann (Eds.), Embodiment, ego-space and action (pp. 179-202). New York, NY: Psychology Press.). The second prediction is that a change in perceptual units should generalize to all relevant actions that are guided using that perceptual information. The same perceptual units can be mapped to different actions. Change in the unit affects all relevant actions. This prediction is consistent with the "general purpose perception approach" (J. M. Loomis & J. W. Philbeck, 2008, Measuring spatial perception with spatial updating and action. In R. L. Klatzky, B. MacWhinney, & M. Behrmann (Eds.), Embodiment, ego-space and action (pp. 1-43). New York, NY: Psychology Press). In Experiment 1, two targeted actions, throwing and extended reaching were tested to determine if they were comparable in precision and in response to distorted calibration. They were. Comparing these actions, the first prediction was tested in Experiment 2 and confirmed. The second prediction was tested in Experiment 3 and confirmed. The action-specific and general purpose perception approaches each fail to predict the alternative results predicted by the other. Both sets of results were predicted by the mapping among embodied units theory of calibration., (PsycINFO Database Record (c) 2014 APA, all rights reserved.)

G. P. Bingham and M. Lind (2008, Large continuous perspective transformations are necessary and sufficient for accurate perception of metric shape, Perception & Psychophysics, Vol. 70, pp. 524-540) showed that observers could perceive metric shape, given perspective changes ≥ 45° relative to a principal axis of elliptical cylinders. In this article, we tested (a) arbitrary perspective changes of 45°, (b) whether perception gradually improves with more perspective change, (c) speed of rotation, (d) whether this works with other shapes (asymmetric polyhedrons), (e) different slants, and (f) perspective changes >45°. Experiment 1 compared 45° perspective change away from, versus centered on, a principal axis. Observers adjusted an ellipse to match the cross-section of an elliptical cylinder viewed in a stereo-motion display. Experiment 2 tested whether performance would improve gradually with increases in perspective change, or suddenly with a 45° change. We also tested speed of rotation. Experiment 3 tested (a) asymmetric polyhedrons, (b) perspective change beyond 45°, and (c) the effect of slant. The results showed (a) a particular perspective was not required, (b) judgments only improved with ≥ 45° change, (c) speed was not relevant, (d) it worked with asymmetric polyhedrons, (e) slant was not relevant, and (f) judgments remained accurate beyond 45° of change. A model shows how affine operations, together with a symmetry yielded by 45° perspective change, bootstrap perception of metric shape., (PsycINFO Database Record (c) 2014 APA, all rights reserved.)

Bingham and Pagano (1998) described calibration as a mapping from embodied perceptual units to an embodied action unit and suggested that it is an inherent component of perception/action that yields accurate targeted actions. We tested two predictions of this "Mapping Theory." First, calibration should transfer between limbs, because it involves a mapping from perceptual units to an action unit, and thus is functionally specific to the action (Pan, Coats, and Bingham, 2014). We used distorted haptic feedback to calibrate feedforward right hand reaches and tested right and left hand reaches after calibration. The calibration transferred. Second, the Mapping Theory predicts that limb specific calibration should be possible because the units are embodied and anatomy contributes to their scaling. Limbs must be calibrated to one another given potential anatomical differences among limbs. We used distorted haptic feedback to calibrate feedforward reaches with right and left arms simultaneously in opposite directions relative to a visually specified target. Reaches tested after calibration revealed reliable limb specific calibration. Both predictions were confirmed. This resolves a prevailing controversy as to whether calibration is functional (Bruggeman & Warren, 2010; Rieser, Pick, Ashmead, & Garing, 1995) or anatomical (Durgin et al., 2003; Durgin & Pelah, 1999). Necessarily, it is both., (PsycINFO Database Record (c) 2014 APA, all rights reserved.)

We recently found that older adults show reduced learning rates when learning a new pattern of coordinated rhythmic movement. The purpose of this study was to extend that finding by examining the performance of all ages across the lifespan from the 20 s through to the 80 s to determine how learning rates change with age. We tested whether adults could learn to produce a novel coordinated rhythmic movement (90° relative phase) in a visually guided unimanual task. We determined learning rates to quantify changes in learning with age and to determine at what ages the changes occur. We found, as before, that learning rates of participants in their 70 s and 80 s were half those of participants in their 20 s. We also found a gradual slow decline in learning rate with age until approximately age 50, when there was a sudden drop to a reduced learning rate for the 60 though 80 year olds. We discuss possible causes for the "50 s cliff" in perceptuo-motor learning rates and suggest that age related deficits in perception of complex motions may be the key to understanding this result.

Visual perception studies typically focus either on optic flow structure or image structure, but not on the combination and interaction of these two sources of information. Each offers unique strengths in contrast to the other's weaknesses. Optic flow yields intrinsically powerful information about 3D structure, but is ephemeral. It ceases when motion stops. Image structure is less powerful in specifying 3D structure, but is stable. It remains when motion stops. Optic flow and image structure are intrinsically related in vision because the optic flow carries one image to the next. This relation is especially important in the context of progressive occlusion, in which optic flow provides information about the location of targets hidden in subsequent image structure. In four experiments, we investigated the role of image structure in "embodied memory" in contrast to memory that is only in the head. We found that either optic flow (Experiment 1) or image structure (Experiment 2) alone were relatively ineffective, whereas the combination was effective and, in contrast to conditions requiring reliance on memory-in-the-head, much more stable over extended time (Experiments 2 through 4). Limits well documented for visual short memory (that is, memory-in-the-head) were strongly exceeded by embodied memory. The findings support J. J. Gibson's (1979/1986, The Ecological Approach to Visual Perception, Boston, MA, Houghton Mifflin) insights about progressive occlusion and the embodied nature of perception and memory.

Reach-to-grasp movements require information about the distance and size of target objects. Calibration of this information could be achieved via feedback information (visual and/or haptic) regarding terminal accuracy when target objects are grasped. A number of reports suggest that the nervous system alters reach-to-grasp behavior following either a visual or haptic error signal indicating inaccurate reaching. Nevertheless, the reported modification is generally partial (reaching is changed less than predicted by the feedback error), a finding that has been ascribed to slow adaptation rates. It is possible, however, that the modified reaching reflects the system's weighting of the visual and haptic information in the presence of noise rather than calibration per se. We modeled the dynamics of calibration and showed that the discrepancy between reaching behavior and the feedback error results from an incomplete calibration process. Our results provide evidence for calibration being an intrinsic feature of reach-to-grasp behavior.