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The direction of gaze towards or away from an observer has immediate effects on attentional processing in the observer. Previous research indicates that faces with direct gaze are processed more efficiently than faces with averted gaze. We recently reported additional processing advantages for faces that suddenly adopt direct gaze (abruptly shift from averted to direct gaze) relative to static direct gaze (always in direct gaze), sudden averted gaze (abruptly shift from direct to averted gaze), and static averted gaze (always in averted gaze). Because changes in gaze orientation in previous study co-occurred with changes in head orientation, it was not clear if the effect is contingent on face or eye processing, or whether it requires both the eyes and the face to provide consistent information. The present study delineates the impact of head orientation, sudden onset motion cues, and gaze cues. Participants completed a target-detection task in which head position remained in a static averted or direct orientation while sudden onset motion and eye gaze cues were manipulated within each trial. The results indicate a sudden direct gaze advantage that resulted from the additive role of motion and gaze cues. Interestingly, the orientation of the face towards or away from the observer did not influence the sudden direct gaze effect, suggesting that eye gaze cues, not face orientation cues, are critical for the sudden direct gaze effect.

The planning and adjusting of one's actions in relation to an action partner is fundamental to smooth joint action. During their first years of life, children gradually become more engaged in joint actions. Here, we investigated whether and at what age children take their partner into account in their action plans to accommodate the other's actions. We focused on children's proactive planning (without prior experience) and flexible adjustment of action plans over time. In a behavioural study, we tested 96 children from four age groups (2½, 3, 3½ and 5 years) in a joint cup-stacking task. Children passed cups to their partner who had only one hand available (alternating over time) to build a tower. Children's response choices were assessed (i.e. passing the cup on the free or occupied side to their partner). The study yielded two major findings. At all ages, children proactively planned their actions in a way that accommodated their partner's actions. However, only by 3½ years did children start to flexibly integrate their partner into their action plans. Even at age 5, children only showed minimal adjustments to their action partner. Candidate processes underlying these developmental changes (e.g. inhibitory control, cognitive flexibility, perspective taking) are discussed., (© 2016 The Author(s).)

A large body of work has established an influence of other people's actions on our own actions. For example, actors entrain to the movements of others, in studies that typically employ continuous movements. Likewise, studies on co-representation have shown that people automatically co-represent a co-actor's task, in studies that typically employ discrete actions. Here we examined entrainment and co-representation within a single task paradigm. Participants sat next to a confederate while simultaneously moving their right hand back and forth between two targets. We crossed whether or not the participant and the confederate moved over an obstacle and manipulated whether participants generated discrete or continuous movement sequences, while varying the space between the actors and whether the actors could see each other's movements. Participants moved higher when the confederate cleared an obstacle than when he did not. For continuous movements, this effect depended on the availability of visual information, as would be expected on the basis of entrainment. In contrast, the co-actor's task modulated the height of discrete movements, regardless of the availability of visual information, which is consistent with co-representation. Space did not have an effect. These results provide new insights into the interplay between co-representation and entrainment for discrete- and continuous-action tasks.

Direct eye contact and motion onset both constitute powerful cues that capture attention. Recent research suggests that (social) gaze and (non-social) motion onset influence information processing in parallel, even when combined as sudden onset direct gaze cues (i.e., faces suddenly establishing eye contact). The present study investigated the role of eye visibility for attention capture by these sudden onset face cues. To this end, face direction was manipulated (away or towards onlooker) while faces had closed eyes (eliminating visibility of eyes, Experiment 1), wore sunglasses (eliminating visible eyes, but allowing for the expectation of eyes to be open, Experiment 2), and were inverted with visible eyes (disrupting the integration of eyes and faces, Experiment 3). Participants classified targets appearing on one of four faces. Initially, two faces were oriented towards participants and two faces were oriented away from participants. Simultaneous to target presentation, one averted face became directed and one directed face became averted. Attention capture by face direction (i.e., facilitation for faces directed towards participants) was absent when eyes were closed, but present when faces wore sunglasses. Sudden onset direct faces can, hence, induce attentional capture, even when lacking eye cues. Inverted faces, by contrast, did not elicit attentional capture. Thus, when eyes cannot be integrated into a holistic face representation they are not sufficient to capture attention. Overall, the results suggest that visibility of eyes is neither necessary nor sufficient for the sudden direct face effect., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Recent evidence suggests the existence of we-mode processing, but little is still known about how such processing influences the sense of control during intentional joint actions. To examine this issue, dyads performed a video game in which they moved a dot to the target of their choice out of a set of targets. By having each participant control the dot movements in only one dimension (orthogonal to their partner) and by varying the target locations, participants took on different roles. By chance, they also could have congruent or incongruent intentions prior to the movements. In a decider-follower scenario, where one actor decided on the target, judgments of control and judgments of performance depended on whether a prior intention was instantiated, but not on actor role. This finding is consistent with we-mode processing. When participants had conflicting intentions that needed to be resolved online, both the dominant and the nondominant participant showed a marked reduction in the perceived quality of the performance. Thus, dynamic intention negotiation reduced we-mode processing and shifted it toward I-mode processing. The nondominant actor also reported a strongly reduced sense of control. Implications for theories on the sense of agency and for applied settings are discussed., (Copyright © 2015 Elsevier B.V. All rights reserved.)

An important functional question for understanding how people perform physical actions is to understand how they manipulate objects. Previous research suggests that people prefer to move their hands symmetrically. For bimanual object manipulation, such symmetry may take on several forms, however. Actions may be symmetrical when objects are grasped (start symmetry), when they are placed on their target locations (target symmetry), and/or relative to the objects being moved (object symmetry). We studied how these forms of symmetry influenced grasp selection when participants moved two plungers from two start locations to two target locations. We varied the heights of these locations across conditions. The grasp locations participants adopted indicated a preference for object symmetry. This preference was even stronger when initial symmetry coincided with object symmetry. These results provide a tractable illustration of how multiple planning constraints may interact to give rise to both regularity and flexibility in motor behavior.

Direct eye contact and motion onset are two powerful cues that capture attention. In the present study, we combined direct gaze with the sudden onset of motion to determine whether these cues have independent or shared influences. Participants identified targets presented randomly on one of four faces. Initially, two faces depicted direct gaze, and two faces depicted averted gaze. Simultaneously with or 900 ms before target presentation, one face with averted gaze switched to direct gaze, and one face with direct gaze switched to averted gaze. When gaze transitions and target presentation were simultaneous, the greatest response-time facilitation occurred at the location of the sudden onset of direct gaze. When target presentation was delayed, direct-gaze cues maintained a facilitatory influence, whereas motion cues induced an inhibitory influence. These findings reveal that gaze cues and motion cues at the same location influence information processing via independent and concurrently acting social and nonsocial attention channels.

Recent findings suggest that tracking others' beliefs is not always effortful and slow, but may rely on a fast and implicit system. An untested prediction of the automatic belief tracking account is that own and others' beliefs should be activated in parallel. We tested this prediction measuring continuous movement trajectories in a task that required deciding between two possible object locations. We independently manipulated whether participants' belief about the object location was true or false and whether an onlooker's belief about the object location was true or false. Manipulating whether or not the agent's belief was ever task relevant allowed us to compare performance in an explicit and implicit version of the same task. Movement parameters revealed an influence of the onlooker's irrelevant belief in the implicit version of the task. This provides evidence for parallel activation of own and others' beliefs., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Many actions involve multiple action steps, which raises the question how far ahead people plan when they perform such actions. Here, we examined higher-order planning for action sequences and whether people planned similarly or differently when acting individually or together with an action partner. For individual performances, participants picked up an object with one hand and passed it to their other hand before placing it onto a target location. For joint performances, they picked up the object and handed it to their action partner, who placed it onto the target location. Each object could be grasped at only two possible grasping positions, implying that the first selected grasp on the object determined the postures for the rest of the action sequence. By varying the height of the target shelf, we tested whether people planned ahead and modulated their grasp choices to avoid uncomfortable end postures. Our results indicated that participants engaged in higher-order planning, but needed task experience before demonstrating such planning during both individual and joint performances. The rate of learning was similar in the two conditions, and participants transferred experience from individual to joint performance. Our results indicate similarity in mechanisms underlying individual and joint action sequence planning.

When two or more individuals intend to achieve a joint outcome, they often need to time their own actions carefully with respect to those of their coactors. Online perceptual feedback supports coordination by allowing coactors to entrain with and predict each other's actions. However, joint actions are still possible when no or little online feedback is available. The current study investigated the interplay between higher-level planning processes and motor simulation in a joint action task where online feedback was not available. Pairs of participants performed forward jumps (hops) next to each other with the instruction to land at the same time. They could neither see nor hear each other, but were informed about their own and the partner's jumping distance beforehand. The analysis of basic movement parameters showed that participants adjusted the temporal and spatial properties of the movement preparation and execution phase of their jumps to the specific difference in distance between themselves and their partner. However, this adaptation was made exclusively by the person with the shorter distance to jump, indicating a distribution of coactors' efforts based on task characteristics. A comparison with an individual bipedal coordination condition suggests that joint coordination might rely on similar principles as interlimb coordination. These findings are interpreted within a framework of motor simulation., (PsycINFO Database Record (c) 2013 APA, all rights reserved.)

The sense of agency has received much attention in the context of individual action but not in the context of joint action. We investigated how the sense of agency developed during individual and dyadic performance while people learned a haptic coordination task. The sense of agency increased with better performance in all groups. Individuals and dyads showed a differential sense of agency after initial task learning, with dyads showing a minimal increase. The sense of agency depended on the context in which the task was first learnt, as transfer from joint to individual performance resulted in an illusory boost in the sense of agency. Whereas the quality of performance related to the sense of agency, the generated forces to achieve the task did not. Our findings are consistent with a predictive model account at the perceptual level, such that the sense of agency relies most strongly on sharable perceptual information., (Copyright © 2012 Elsevier Inc. All rights reserved.)

People often perform actions that involve a direct physical coupling with another person, such as when moving furniture together. Here, we examined how people successfully coordinate such actions with others. We tested the hypothesis that dyads amplify their forces to create haptic information to coordinate. Participants moved a pole (resembling a pendulum) back and forth between two targets at different amplitudes and frequencies. They did so by pulling on cords attached to the base of the pole, one on each side. In the individual condition, one participant performed this task bimanually, and in the joint condition two participants each controlled one cord. We measured the moment-to-moment pulling forces on each cord and the pole kinematics to determine how well individuals and dyads performed. Results indicated that dyads produced much more overlapping forces than individuals, especially for tasks with higher coordination requirements. Thus, the results suggest that dyads amplify their forces to generate a haptic information channel. This likely reflects a general coordination principle in haptic joint action, where force amplification allows dyads to perform at the same level as individuals.

Performing joint actions often requires precise temporal coordination of individual actions. The present study investigated how people coordinate their actions at discrete points in time when continuous or rhythmic information about others' actions is not available. In particular, we tested the hypothesis that making oneself predictable is used as a coordination strategy. Pairs of participants were instructed to coordinate key presses in a two-choice reaction time task, either responding in synchrony (Experiments 1 and 2) or in close temporal succession (Experiment 3). Across all experiments, we found that coactors reduced the variability of their actions in the joint context compared with the same task performed individually. Correlation analyses indicated that the less variable the actions were, the better was interpersonal coordination. The relation between reduced variability and improved coordination performance was not observed when pairs of participants performed independent tasks next to each other without intending to coordinate. These findings support the claim that reducing variability is used as a coordination strategy to achieve predictability. Identifying coordination strategies contributes to the understanding of the mechanisms involved in real-time coordination.

We studied whether motor-control constraints for grasping objects that are moved to new positions reflect a rigid constraint hierarchy or a flexible constraint hierarchy. In two experiments, we asked participants to move two plungers from the same start locations to different target locations (both high, both low, or one high and one low). We found that participants grasped the plungers symmetrically and at heights that ensured comfortable or easy-to-control end postures when the plungers had the same target heights, but these grasp tendencies were reduced when the plungers had different target heights. In addition, when the plungers had different mass distributions, participants behaved in ways that suggested still-different emphases of the relevant grasp constraints. When the plungers had different mass distributions, participants sacrificed bimanual symmetry for end-state comfort. The results suggest that bimanual grasp planning relies on a flexible rather than static hierarchy. Different constraints take on different degrees of importance depending on the nature of the task and on the level of task experience. The results have implications for the understanding of perceptual-motor skill learning. It may be that one mechanism underlying such learning is changing the priorities of task constraints.

Qualitative and quantitative changes characterize locomotion and rhythmic interlimb coordination at different speeds. Legs and hands do not move more or less quickly; they also adopt different relative coordination patterns. In the present article, the authors asked whether similar transitions occur for unimanual hand movements when speed is slowed below the preferred speed. Participants moved a handheld dowel back and forth between 2 large circular targets in time with a metronome at periods between 370 ms and 1667 ms. The authors analyzed the kinematics of participants' movements at each period and found that proportional dwell time and number of peaks in the velocity profile increased as driving periods increased. Path lengths and peak velocities remained relatively constant for driving periods exceeding 800 ms. Participants made only gradual changes to their movement parameters, so that they went from a continuous mode to a more discrete mode of behavior for longer driving periods. Thus, unlike for rhythmic bimanual movements or locomotory patterns, there are quantitative but no clear qualitative changes for unimanual movements. The results suggest that participants tried to move close to their preferred tempo at different rates, and that they avoided moving slowly.

M. J. Spivey, M. Grosjean, and G. Knoblich showed that in a phonological competitor task, participants' mouse cursor movements showed more curvature toward the competitor item when the competitor and target were phonologically similar than when the competitor and target were phonologically dissimilar. Spivey et al. interpreted this result as evidence for continuous cascading of information during the processing of spoken words. Here we show that the results of Spivey et al.need not be ascribed to continuous speech processing. Instead, their results can be ascribed to discrete processing of speech, provided one appeals to an already supported model of motor control that asserts that switching movements from 1 target to another relies on superposition of the 2nd movement onto the 1st. The latter process is a continuous cascade, a fact that indirectly strengthens the plausibility of continuous cascade models. However, the fact that we can simulate the results of Spivey et al.with a continuous motor output model and a discrete perceptual model shows that the implications of Spivey et al.'s experiment are less clear than these authors supposed., ((c) 2009 APA, all rights reserved.)

Previous research suggests that motor equivalence is achieved through reliance on effector-independent spatiotemporal forms. Here the authors report a series of experiments investigating the role of such forms in the production of movement sequences. Participants were asked to complete series of arm movements in time with a metronome and, on some trials, with an obstacle between 1 or more of the target pairs. In moves following an obstacle, participants only gradually reduced the peak heights of their manual jumping movements. This hand path priming effect, scaled with obstacle height, was preserved when participants cleared the obstacle with 1 hand and continued with the other, and it was modulated by future task demands. The results are consistent with the hypothesis that the control of movement sequences relies on abstract spatiotemporal forms. The data also support the view that motor programming is largely achieved by changing just those features that distinguish the next movement to be made from the movement that was just made., ((c) 2007 APA)

Although locomotion and prehension are commonly coordinated in everyday life, little previous research has focused on this form of coordination. To address this neglected topic, we asked participants to stand a variable distance from a table, walk up to the table, and move an object on the tabletop to a new tabletop position, either to the right or to the left of the object's initial position and near or far from that initial position. For large manual displacements, which required a step after picking up the object, subjects preferred to stand on the foot opposite the direction of forthcoming manual displacement. By contrast, for small manual displacements, which did not require a step after picking up the object, subjects showed no support-leg preference when they grasped the object prior to manual displacement. The support-leg preferences at grasp time were apparently anticipated by participants as they walked up to the table, indicating considerable long-range planning of entire body positions associated with forthcoming object transfers.