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Perceptual learning, improvement in perceptual skill with practice, can improve both accuracy and consistency of perceptual reports. Regression statistics can quantify ongoing calibration of perceptible scalar properties (i.e., improvements in accuracy and consistency) because, ideally, actual and perceived values are linearly related. Changes in variance accounted for ([r.sup.2]) track changes in consistency, and changes in both slope and intercept track changes in accuracy. Conjoint changes in all three regression statistics, obscured in separate plots, can be seen simultaneously in a perceptual calibration state space diagram, with the regression statistics as axes, in which an attractor ([r.sup.2] = 1.00, slope = 1.00, intercept = 0.00) represents optimal performance. Decreases in the distance between the attractor and successive points in the state space, each representing perceptual performance, quantify perceptual learning; that distance is a perceptual calibration index. To show the utility of the perceptual calibration index, we illustrate its use in an experiment on wielding hand-held objects.

During sustained viewing of an ambiguous stimulus, an individual's perceptual experience will generally switch between the different possible alternatives rather than stay fixed on one interpretation (perceptual rivalry). Here, we measured pupil diameter while subjects viewed different ambiguous visual and auditory stimuli. For all stimuli tested, pupil diameter increased just before the reported perceptual switch and the relative amount of dilation before this switch was a significant predictor of the subsequent duration of perceptual stability. These results could not be explained by blink or eye-movement effects, the motor response or stimulus driven changes in retinal input. Because pupil dilation reflects levels of norepinephrine (NE) released from the locus coeruleus (LC), we interpret these results as suggestive that the LC-NE complex may play the same role in perceptual selection as in behavioral decision making. attention | norepinephrine | vision | decision making

A perceptual learning experiment provides evidence that the mental lexicon cannot consist solely of detailed acoustic traces of recognition episodes. In a training lexical decision phase, listeners heard an ambiguous [f-s] fricative sound, replacing either If] or [s] in words. In a test phase, listeners then made lexical decisions to visual targets following auditory primes. Critical materials were minimal pairs that could be a word with either [f] or [s] (cf. English knife-nice), none of which had been heard in training. Listeners interpreted the minimal pair words differently in the second phase according to the training received in the first phase. Therefore, lexically mediated retuning of phoneme perception not only influences categorical decisions about fricatives (Norris, McQueen, & Cutler, 2003), but also benefits recognition of words outside the training set. The observed generalization across words suggests that this retuning occurs prelexically. Therefore, lexical processing involves sublexical phonological abstraction, not only accumulation of acoustic episodes. Keywords: Speech perception; Perceptual learning; Phonological abstraction; Episodic models; Spoken-word recognition

Piriform cortical circuits are hypothesized to form perceptions from responses to specific odorant features, but the anterior piriform cortex (aPCX) and posterior piriform cortex (pPCX) differ markedly in their anatomical organization, differences that could lead to distinct roles in odor encoding. Here, we tested whether experience with a complex odorant mixture would modify encoding of the mixture and its components in aPCX and pPCX. Rats were exposed to an odorant mixture and its components in a go/no-go rewarded odor discrimination task. After reaching behavioral performance criterion, single-unit recordings were made from the aPCX and pPCX in these rats and in odor-naive, control, urethane-anesthetized rats. After odor experience, aPCX neurons were more narrowly tuned to the test odorants, and there was a decorrelation in aPCX population responses to the mixture and its components, suggesting a more distinct encoding of the familiar mixture from its components. In contrast, pPCX neurons were more broadly tuned to the familiar odorants, and pPCX population responses to the mixture and its components became more highly correlated, suggesting a pPCX encoding of similarity between familiar stimuli. The results suggest aPCX and pPCX play different roles in the processing of familiar odors and are consistent with an experience-dependent encoding (perceptual learning) of synthetic odorant identity in aPCX and an experience-dependent encoding of odor similarity or odor quality in pPCX. memory | olfactory discrimination | perceptual learning | odorant mixture | odor encoding

Until half a century ago, associative learning played a fundamental role in theories of perceptual appearance [Berkeley, G. (1709) An Essay Towards a New Theory of Vision (Dublin), 1st Ed.]. But starting in 1955 (Gibson, J. J. & Gibson, E. J. (1955) Psychol. Rev. 62, 32-41], most studies of perceptual learning have not been concerned with association or appearance but rather with improvements in discrimination ability. Here we describe a 'cue recruitment' experiment, which is a straightforward adaptation of Pavlov's classical conditioning experiment, that we used to measure changes in visual appearance caused by exposure to novel pairings of signals in visual stimuli. Trainees viewed movies of a rotating wire-frame (Necker) cube. This stimulus is perceptually bistable. On training trials, depth cues (stereo and occlusion) were added to force the perceived direction of rotation. Critically, an additional signal was also added, contingent on rotation direction. Stimuli on test trials contained the new signal but not the depth cues. Over 45 min, two of the three new signals that we tested acquired the ability to bias perceived rotation direction on their own. Results were consistent across the eight trainees in each experiment, and the new cue's effectiveness was long lasting. Whereas most adaptation aftereffects on appearance are opposite in direction to the training stimuli, these effects were positive. An individual new signal can be recruited by the visual system as a cue for the construction of visual appearance. Cue recruitment experiments may prove useful for reexamining of the role of experience in perception. classical conditioning | perceptual learning | bistable perception

A study on human learning, using linear regrsession, with relation to humans' existing knowledge theory is presented.

For more than a century, the process of stabilization has been a central issue in the research of learning and memory. Namely, after a skill or memory is acquired, it must be consolidated before it becomes resistant to disruption by subsequent learning. Although it is clear that there are many cases in which learning can be disrupted, it is unclear when learning something new disrupts what has already been learned. Herein, we provide two answers to this question with the demonstration that perceptual learning of a visual stimulus disrupts or interferes with the consolidation of a previously learned visual stimulus, in this study, we trained subjects on two different hyperacuity tasks and determined whether learning of the second task disrupted that of the first. We first show that disruption of learning occurs between visual stimuli presented at the same orientation in the same retinotopic location but not for the same stimuli presented at retinotopically disparate locations or different orientations at the same location. Second, we show that disruption from stimuli in the same retinotopic location is ameliorated if the subjects wait for 1 h before training on the second task. These results indicate that disruption, at least in visual learning, is specific to features of the tasks and that a temporal delay of 1 h can stabilize visual learning. This research shows that visual learning is susceptible to disruption and elucidates the processes by which the brain can consolidate learning and thus protect what is learned from being overwritten. plasticity | psychophysics | vision | consolidation | hyperacuity

Perceptual learning is an improvement in one's sensory abilities after training and is thought to help us to better adapt to the sensory environment. Here, we show that perceptual learning also can lead to misperceptions, such that subjects actually perceive stimuli when none are physically presented. After learning, subjects not only showed enhanced performance when tested with the motion direction of the trained stimulus but also often reported seeing dots moving in the trained direction when no stimulus was displayed. We further show that these misperceptions are not attributable to a response bias. These results show that there are costs as well as benefits to perceptual learning and that performance enhancements for a specific feature also can be accompanied by misperceptions of the visual environment. motion | plasticity vision | learning | psychophysics

Repeated within-day testing on a texture discrimination task leads to retinotopically specific decreases in performance. Although perceptual learning has been shown to be highly specific to the retinotopic location and characteristics of the trained stimulus, the specificity of perceptual deterioration has not been studied. We investigated the similarities between learning and deterioration by examining whether deterioration transfers to new distractor or target orientations or to the untrained eye. Participants performed a texture discrimination task in three one-hour sessions. We tested the specificity of deterioration in the final session by switching either the orientation of the background or the target elements by 90[degrees]. We found that performance deteriorated steadily both within and across the first two sessions and was specific to the target but not the distractor orientation. In a separate experiment, we found that deterioration transferred to the untrained eye. Changes in performance were independent of reported sleepiness and awareness of stimulus changes, arguing against the possibility that perceptual deterioration is due to general fatigue. Rather, we hypothesize that perceptual deterioration may be caused by changes in the ability for attention to selectively enhance the responses of relatively low-level orientation-selective sensory neurons, possibly within the primary visual cortex. Further, the differences in specificity profiles between learning and deterioration suggest separate underlying mechanisms that occur within the same cortical area. primary visual cortex | learning | vision | psychophysics | attention

Performance in perceptual tasks often improves with practice. This effect is known as 'perceptual learning,' and it has been the source of a great deal of interest and debate over the course of the last century. Here, we consider the effects of perceptual learning within the context of signal detection theory. According to signal detection theory, the improvements that take place with perceptual learning can be due to increases in internal signal strength or decreases in internal noise. We used a combination of psychophysical techniques (external noise masking and double-pass response consistency) that involve corrupting stimuli with externally added noise to discriminate between the effects of changes in signal and noise as observers learned to identify sets of unfamiliar visual patterns. Although practice reduced thresholds by as much as a factor of 14, internal noise remained virtually fixed throughout training, indicating learning served to predominantly increase the strength of the internal signal. We further examined the specific nature of the changes that took place in signal strength by correlating the externally added noise with observer's decisions across trials (response classification). This technique allowed us to visualize some of the changes that took place in the linear templates used by the observers as learning occurred, as well as test the predictions of a linear template-matching model. Taken together, the results of our experiments offer important new theoretical constraints on models of perceptual learning. Keywords: Perceptual learning; Internal noise; Internal signal; Ideal observer; Classification image

Previous research indicates that after standard instruction, students at all levels often construct a conceptual framework in which the ideas of absolute simultaneity and the relativity of simultaneity co-exist. We describe the development and assessment of instructional materials intended to improve student understanding of the concept of time in special relativity, the relativity of simultaneity, and the role of observers in inertial reference frames. Results from pretests and post-tests are presented to demonstrate the effect of the curriculum in helping students deepen their understanding of these topics. Excerpts from taped interviews and classroom interactions help illustrate the intense cognitive conflict that students encounter as they are led to confront the incompatibility of their deeply held beliefs about simultaneity with the results of special relativity.

The brain's sensory processing systems are modified during perceptual learning. To learn more about the spatial organization of learning-related modifications, we trained rats to utilize the sensory signal from a single intact whisker to carry out a behavioral task. Once a rat had mastered the task, we clipped its 'trained' whisker and attached a 'prosthetic' one to a different whisker stub. We then tested the rat to determine how quickly it could relearn the task by using the new whisker. We observed that rats were immediately able to use the prosthetic whisker if it were attached to the stub of the trained whisker but not if it were attached to a different stub. Indeed, the greater the distance between the trained and prosthetic whisker, the more trials were needed to relearn the task. We hypothesized that this 'transfer' of learning between whiskers might depend on how much the representations of individual whiskers overlap in primary somatosensory cortex. Testing this hypothesis by using 100-electrode cortical recordings, we found that the overlap between the cortical response patterns of two whiskers accounted well for the transfer of learning between them: The correlation between the electrophysiological and behavioral data was very high (r = 0.98). These findings suggest that a topographically distributed memory trace for sensory-perceptual learning may reside in primary sensory cortex.

A study was conducted to analyze the hypothesis that the nature of categorization can influence the perceived properties of an identical distal object. Two change-detection experiments were carried out. Results indicated that the acquisition of category expertise at the subordinate level is similar to the acquisition of perceptual expertise. Findings also showed a change in the representation of identical objects because the change-detection paradigm probed the perception of the objections.

Degraded images of objects or faces appear meaningless at first, but are easily recognizable after an original version of the image is viewed. The neural mechanisms responsible for speeding up the learning process are ill understood but it is thought that it involves several visual and spatial systems. A new study uses functional neuroimaging to discover the areas of the brain involved in such rapid perceptual learning. It is suggested that direct interactions between areas involved in feature binding, spatial attention, face recognition and memory recall are implicated in perceptual learning.

Medical research using transcranial magnetic stimulation indicates thatblind human beings who lost their sight when they were very young have a visual cortex which processes somato-sensory input. Evidence suggests that cross-modal plasticity helps blind people to develop very good tactile perceptual skills. The clinical characteristics of blind people are shown.

Research into the specificity of perceptual learning indicates that learning generalizes across orientation and retinal position in the case of easy learning conditions. When learning tasks are made harder, learning grows more specific in terms of both orientation and position. It is possible to conclude that modifications take place at various levels of the visual system, in reverse hierarchical order. Apparently contradictory data can be explained by attributing strategies for improvement which appear different from changes within different underlying neuronal sites.

Does perceptual grouping require attention? Recent controversy on this question may be caused by a conflation of two aspects of grouping: element clustering (determining which elements belong together) and shape formation (determining cluster boundaries). In Experiment 1, observers enumerated diamonds that were drawn with either lines or dots. These two types of stimuli were subitized (enumerated rapidly and accurately in the range from one to three items) equally well, suggesting that clustering dots into countable entities did not demand attention. In contrast, when target diamonds were enumerated among distractor squares in Experiment 2, only line-drawn items could be subitized. We propose that clustering and shape formation not only involve different perceptual processes, but play different functional roles in vision., Two experiments on the enumeration of clusters and specific shapes were conducted to demonstrate that clustering and shape formation are separable operations that have different attentional requirements. The strategy used tested the importance of element connectedness in two enumeration tasks. These operations are decoupled empirically, and since they serve different functional roles in vision, further research on perpetual grouping should profit from taking distinctions into consideration.

The specificity of the improvement in perceptual learning is often used to localize the neuronal changes underlying this type of adult plasticity. We investigated a visual texture discrimination task previously reported to be accomplished preattentively and for which learning-related changes were inferred to occur at a very early level of the visual processing stream. The stimulus was a matrix of lines from which a target popped out, due to an orientation difference between the three target lines and the background lines. The task was to report the global orientation of the target and was performed monocularly. The subjects' performance improved dramatically with training over the course of 2-3 weeks, after which we tested the specificity of the improvement for the eye trained. In all subjects tested, there was complete interocular transfer of the learning effect. The neuronal correlates of this learning are therefore most likely localized in a visual area where input from the two eyes has come together.

Perceptual learning - the improvement of perceptual skills through practice - is a type of human learning that may serve as a paradigm for the acquisition and retention of procedural [...], Several paradigms of perceptual learning suggest that practice can trigger long-term, experience-dependent changes in the adult visual system of humans. As shown here, performance of a basic visual discrimination task improved after a normal night's sleep. Selective disruption of rapid eye movement (REM) sleep resulted in no performance gain during a comparable sleep interval, although non-REM slow-wave sleep disruption did not affect improvement. On the other hand, deprivation of REM sleep had no detrimental effects on the performance of a similar, but previously learned, task. These results indicate that a process of human memory consolidation, active during sleep, is strongly dependent on REM sleep.

This article offers some novel ideas to the age-old debate within the helping professions about how to gain balance between an analytical, cognitive style of processing data and the more experiential and humanistic process of direct perception. Ideas drawn from the perceptual skills training are combined with therapeutic techniques from Gestalt therapy. This marriage of ideas can be helpful in training counselors to understand and experience how techniques used by artists to see objects realistically can be applied to a counseling relationship.

Experiments on speech perception determine how familiarity with a talker's voice affects perception of spoken words. Two trained groups identified novel words produced by either the same or different group of talkers. Results show the ability to identify a talker's voice improves intelligibility of the words used. Speech perception may involve talker-contingent processes, whereby the perceptual learning of vocal source facilitates the phonetic analysis of the acoustic signal, subsequently.

The characteristics of automatized performance resemble those of preattentive processing in some respects. In the context of visual search tasks, these include spatially parallel processing, involuntary calling of attention, learning without awareness, and time-sharing with other tasks. However, this article reports some evidence suggesting that extended practice produces its effects through different mechanisms from those that underlie preattentive processing. The dramatic changes in search rate seem to depend not on the formation of new preattentive detectors for the task-relevant stimuli, nor on learned abstracted procedures for responding quickly and efficiently, but rather on changes that are very specific both to the particular stimuli and to the particular task used in practice. We suggest that the improved performance may depend on the accumulation of separate memory traces for each individual experience of a display (see Logan, 1988), and we show that the traces differ for conjunction search in which stimuli must be individuated and for feature search where a global response to the display is sufficient.

New research supports connectionist network models and classical learning theories indicating that learning boosts the strength of discriminate signals. It is still unclear how signal enhancement shows itself at the neuronal level. This research involved making sets of faces and textures whose signal strength could be changed. Observers were trained to identify these patterns embedded in noise. Performance improved by up to 400% across a number of sessions. Learning boosted the efficiency with which observers encoded task-relevant information. It appears that the neural correlates of behaviour should show improved discrimination among stimuli and constant variability during perceptual learning.

A hallmark of perceptual expertise is that experts classify objects at a more specific, subordinate level of abstraction than novices. To what extent does subordinate-level learning contribute to the transfer of perceptual expertise to novel exemplars and novel categories? In this study, participants learned to classify 10 varieties of wading birds and 10 varieties of owls at either the subordinate, species (e.g., 'great blue crown heron,''eastern screech owl') or the family ('wading bird,''owl') level of abstraction. During training, the amount of visual exposure was equated such that participants received an equal number of learning trials for wading birds and owls. Pre- and posttraining performance was measured in a same/different discrimination task in which participants judged whether pairs of bird stimuli belonged to the same or different species. Participants trained in species-level discrimination demonstrated greater transfer to novel exemplars and novel species categories than participants trained in family-level discrimination. These findings suggest that perceptual categorization, not perceptual exposure per se, is important for the development and generalization of visual expertise.

Teachers gesture when they teach, and those gestures do not always convey the same information as their speech. Gesture thus offers learners a second message. To determine whether learners take advantage of this offer, we gave 160 children in the third and fourth grades instruction in mathematical equivalence. Children were taught either one or two problem-solving strategies in speech accompanied by no gesture, gesture conveying the same strategy, or gesture conveying a different strategy. The children were likely to profit from instruction with gesture, but only when it conveyed a different strategy than speech did. Moreover, two strategies were effective in promoting learning only when the second strategy was taught in gesture, not speech. Gesture thus has an active hand in learning.

The nonhumans capability to form conceptual versus perceptual discriminations is discussed. In this connection, a young gorilla was trained at three levels of abstraction that is concrete, intermediate and abstract, which showed that the gorilla was able to discriminate positive from the negative exemplars.

Perceptual organization offers an elegant framework to group low-level features that are likely to come from a single object. We offer a novel strategy to adapt this grouping process to objects in a domain. Given a set of training images of objects in context, the associated learning process decides on the relative importance of the basic salient relationships such as proximity, parallelness, continuity, junctions, and common region toward segregating the objects from the background. The parameters of the grouping process are cast as probabilistic specifications of Bayesian networks that need to be learned. This learning is accomplished using a team of stochastic automata in an N-player cooperative game framework. The grouping process, which is based on graph partitioning is, able to form large groups from relationships defined over a small set of primitives and is fast. We statistically demonstrate the robust performance of the grouping and the learning frameworks on a variety of real images. Among the interesting conclusions are the significant role of photometric attributes in grouping and the ability to form large salient groups from a set of local relations, each defined over a small number of primitives. Index Terms--Perceptual organization, learning in vision, learning automata, Bayesian networks, feature grouping, object recognition, figure ground segmentation.

A detailed computational model for learning spatial networks is presented. Information is kept in a distributed, modular format: 'condition-actions pairs.' Knowledge of individual routes consists in chaining this piecemeal information. The model, called the Traveller, was fully implemented, and some sample runs are discussed. In learning a new network, the model displays the well-known transition from route level to survey level knowledge. No special mechanisms are needed to achieve the transition, as the Traveller's interactions with the environment gradually structure its emerging cognitive map. The Traveller is compared with some of the main competing computational models, and evidence from empirical research is adduced to support the suggested representational format.

Helmholtz's unconscious inference models and Gibson's general solution to ambiguity offer explanations on where the deficit in the visual localization process takes place. The former maintains that any incorrect value for retinal position or eye position would yield an incorrect calculation, while the latter states that the position of an object is determined by its relation to other things, with judgment on its location depending on the perspective adopted by the viewer when using the frame of reference.