The perception of handshapes in American Sign Language

Despite the constantly varying stream of sensory information that surrounds us, we humans can discern the small building blocks of words that constitute language (phonetic forms) and perceive them categorically (categorical perception, CP). Decades of controversy have prevailed regarding what is at the heart of CP, with many arguing that it is due to domain-general perceptual processing and others that it is determined by the existence of domain-specific linguistic processing. What is most key: perceptual or linguistic patterns? Here, we study whether CP occurs withsoundless handshapes that are nonethelessphonetic in American Sign Language (ASL), in signers and nonsigners. Using innovative methods and analyses of identification and, crucially, discrimination tasks, we found that both groups separated the soundless handshapes into two classes perceptually but that only the ASL signers exhibited linguistic CP. These findings suggest that CP of linguistic stimuli is based on linguistic categorization, rather than on purely perceptual categorization.     

To judge a book by its weight you need to know its content: Knowledge moderates the use of embodied cues

Participants evaluated a book as more important when it weighed heavily in their hands (due to a concealed weight), but only when they had substantive knowledge about the book. Those who had read a synopsis (Study 1), had read the book (Study 2) and knew details about its plot (Study 3) were influenced by its weight, whereas those unfamiliar with the book were not. This contradicts the widely shared assumption that metaphorically related perceptual inputs serve as heuristic cues that people primarily use in the absence of more diagnostic information. Instead, perceptual inputs may increase the accessibility of metaphorically congruent knowledge or may suggest an initial hypothesis that is only endorsed when supporting information is accessible.     

Are there representational shifts during category learning?

Early theories of categorization assumed that either rules, or prototypes, or exemplars were exclusively used to mentally represent categories of objects. More recently, hybrid theories of categorization have been proposed that variously combine these different forms of category representation. Our research addressed the question of whether there are representational shifts during category learning. We report a series of experiments that tracked how individual subjects generalized their acquired category knowledge to classifying new critical transfer items as a function of learning. Individual differences were observed in the generalization patterns exhibited by subjects, and those generalizations changed systematically with experience. Early in learning, subjects generalized on the basis of single diagnostic dimensions, consistent with the use of simple categorization rules. Later in learning, subjects generalized in a manner consistent with the use of similarity-based exemplar retrieval, attending to multiple stimulus dimensions. Theoretical modeling was used to formally corroborate these empirical observations by comparing fits of rule, prototype, and exemplar models to the observed categorization data. Although we provide strong evidence for shifts in the kind of information used to classify objects as a function of categorization experience, interpreting these results in terms of shifts in representational systems underlying perceptual categorization is a far thornier issue. We provide a discussion of the challenges of making claims about category representation, making reference to a wide body of literature suggesting different kinds of representational systems in perceptual categorization and related domains of human cognition.     

On the relation between decision rules and perceptual representation in multidimensional perceptual categorization

This article examines the relation between changing categorization decision rules and the nature of the underlying perceptual representation. Observers completed a matching task that required them to adjust the length and orientation of a single line stimulus until they perceived it to "match" a second line stimulus (Alfonso-Reese, 1996, 1997). The same observers then completed four categorization tasks with the same stimuli. Data from the matching task were used to estimate a perceptual representation for each stimulus and observer. Three hypotheses regarding potential interactions between categorization decision rules and perceptual representation were examined. One assumed that there was no interaction between decision rules and perceptual representation. The second assumed that linear categorization rules affect the perceptual representation differently from nonlinear categorization rules. The third assumed that dimensional integration rules affected the perceptual representation differently from decision rules that require the observer to set a criterion along one stimulus dimension while ignoring the other; this is referred to as decisional selective attention. The results suggested that (1) the matching task perceptual representation provided a good account of the categorization data, (2) decisional selective attention affected the perceptual representation differently from decisional integration, and (3) decisional selective attention generally decreased the perceptual variability along the attended dimension.     

Separating perceptual processes from decisional processes in identification and categorization

Four observers completed perceptual matching, identification, and categorization tasks using separable-dimension stimuli. A unified quantitative approach relating perceptual matching, identification, and categorization was proposed and tested. The approach derives from general recognition theory (Ashby & Townsend, 1986) and provides a powerful method for quantifying the separate influences of perceptual processes and decisional processes within and across tasks. Good accounts of the identification data were obtained from an initial perceptual representation derived from perceptual matching. The same perceptual representation provided a good account of the categorization data, except when selective attention to one stimulus dimension was required. Selective attention altered the perceptual representation by decreasing the perceptual variance along the attended dimension. These findings suggest that a complete understanding of identification and categorization performance requires an understanding of perceptual and decisional processes. Implications for other psychological tasks are discussed.     

Separating perceptual processes from decisional processes in identification and categorization.

Four observers completed perceptual matching, identification, and categorization tasks using separable-dimension stimuli. A unified quantitative approach relating perceptual matching, identification, and categorization was proposed and tested. The approach derives from general recognition theory (Ashby & Townsend, 1986) and provides a powerful method for quantifying the separate influences of perceptual processes and decisional processes within and across tasks. Good accounts of the identification data were obtained from an initial perceptual representation derived from perceptual matching. The same perceptual representation provided a good account of the categorization data, except when selective attention to one stimulus dimension was required. Selective attention altered the perceptual representation by decreasing the perceptual variance along the attended dimension. These findings suggest that a complete understanding of identification and categorization performance requires an understanding of perceptual and decisional processes. Implications for other psychological tasks are discussed.     

Learning and attention in multidimensional identification and categorization: separating low-level perceptual processes and high-level decisional processes

Four observers completed identification and categorization tasks. Learning and attention processes were examined by applying general recognition theory (F. G. Ashby & J. T. Townsend, 1986), which separates perceptual, decisional, and attentional processes. Learning led to decision regions that became more nearly optimal. Learning had little effect on perceptual processes in identification and decisional integration categorization tasks but affected perceptual processes in decisional selective attention categorization tasks, leading to perceptual selective attention. These findings suggest that (a) identification and categorization invoke decision strategies that are localized in the striatum (F. G. Ashby, E. M. Waldron, W. W. Lee, & A. Berkman, 2001) and (b) perceptual and decisional attention systems exist and are mediated by distinct brain structures (M. I. Posner & S. E. Petersen, 1990).     

知觉与行为分离现象在二维铁钦纳错觉实验中的验

利用二维铁钦纳错觉图片对单手及双手抓握情境下的知觉与行为分离现象进行实验验证,并探讨注意引导等因素对分离现象的影响。实验包括知觉任务和行为任务两项内容,前者主要测量被试的主观错觉量,后者则探讨分离现象是否存在及其影响因素。在行为任务中,记录被试在中心（目标）圆尺寸“实际相同”和“知觉相同”等不同情境下的行为,以拇指和食指抓握图片中心圆的最大抓握孔径为行为指标。结果发现：单手抓握时,左、右手的行为虽然在一定程度上受到了错觉的影响,但均显示出分离现象;双手抓握时,右手受错觉影响的程度减少,分离现象增强,而左手的结果则比较混淆。因此,分离现象是存在的,但它的出现可能受到注意引导、注意分配倾向或双手协调能力等因素的影响。     

The feeling of fluent perception: a single experience from multiple asynchronous sources

Zeki and co-workers recently proposed that perception can best be described as locally distributed, asynchronous processes that each create a kind of microconsciousness, which condense into an experienced percept. The present article is aimed at extending this theory to metacognitive feelings. We present evidence that perceptual fluency-the subjective feeling of ease during perceptual processing-is based on speed of processing at different stages of the perceptual process. Specifically, detection of briefly presented stimuli was influenced by figure-ground contrast, but not by symmetry (Experiment 1) or the font (Experiment 2) of the stimuli. Conversely, discrimination of these stimuli was influenced by whether they were symmetric (Experiment 1) and by the font they were presented in (Experiment 2), but not by figure-ground contrast. Both tasks however were related with the subjective experience of fluency (Experiments 1 and 2). We conclude that subjective fluency is the conscious phenomenal correlate of different processing stages in visual perception.     

On the relation between justification of solution method and correctness of solution in statistical problem solving

The relation between the justification of a choice of solution method and the correctness of that choice in statistical problem solving was investigated. In the first of two studies 16 subjects were asked to think aloud while solving two statistical problems. The results showed that an incorrect choice of solution method was more common when subjects did not justify their choice of solution as compared to when they justified their choice with domain-specific knowledge. Study 2 employed an experimental design. A group of 20 subjects were instructed to provide a justification for each choice of solution method, while another group of 20 subjects received no such instructions. The results showed no difference between the groups with respect to number of correct choices of solution method. A qualitative analysis of the justifications in the instructed group showed that the justifications for incorrect solution methods were more often incorrect than subjects' justifications for correct solution methods. The results in Study 2 suggested that the association found between incorrect choice of solution method and lack of justification in Study 1 was not in the first place due to a strategical deficiency on the part of the subjects but due to a lack of domain-specific knowledge.     

The role of motion in children's categorization of objects.

Perceptual cues play a fundamental role in early categorization of objects. What is meant by perceptual cues in the literature, however, is not always clear. It is fair to say that they are typically understood to be static shape cues. A number of recent studies have suggested that dynamic perceptual cues, such as motion, may also be important in early categorization. The study presented here explored the role that motion plays in children's categorization of animal and non-animal kinds, such as geometric figures. Motion was directly pitted against shape as a cue for categorization. Results showed that 4-year-old children, confronted with a choice between shape and motion, significantly used motion cues over shape cues to categorize objects, regardless of whether they were animals or geometric figures. Seven-year-olds also tended to use motion more often to categorize animals but not when dealing with geometric figures. Older children, who have been found to have a clearer natural kind/artifact distinction, seem to appreciate the uniqueness of movement to animals and see motion as more relevant to their categorization but relatively less so to categorize geometric figures. This developmental shift in the categorization of animals and geometric figures based on motion was further confirmed by testing adults on the same tasks. Adults were found to base their judgements significantly more often on motion for animals but not for geometric figures. These findings support the view that children are initially guided by motion in object categorization, suggesting that motion plays an overriding role that is central in the process of concept acquisition and in the mechanisms by which concepts are later structured.     

Similarity and categorization: from vision to touch

Even though human perceptual development relies on combining multiple modalities, most categorization studies so far have focused on the visual modality. To better understand the mechanisms underlying multisensory categorization, we analyzed visual and haptic perceptual spaces and compared them with human categorization behavior. As stimuli we used a three-dimensional object space of complex, parametrically-defined objects. First, we gathered similarity ratings for all objects and analyzed the perceptual spaces of both modalities using multidimensional scaling analysis. Next, we performed three different categorization tasks which are representative of every-day learning scenarios: in a fully unconstrained task, objects were freely categorized, in a semi-constrained task, exactly three groups had to be created, whereas in a constrained task, participants received three prototype objects and had to assign all other objects accordingly. We found that the haptic modality was on par with the visual modality both in recovering the topology of the physical space and in solving the categorization tasks. We also found that within-category similarity was consistently higher than across-category similarity for all categorization tasks and thus show how perceptual spaces based on similarity can explain visual and haptic object categorization. Our results suggest that both modalities employ similar processes in forming categories of complex objects.     

You heard it here first: Readers mentally simulate described sounds

The present experiments examined whether readers spontaneously simulate implied auditory elements of sentences. Participants read sentences that implicitly conveyed details that could provoke auditory imagery (e.g., The engine clattered as the truck driver warmed up his rig.), and then performed an unrelated sound categorization task during which they classified sounds as real (occurring in the world) or fake (computer generated). In Experiment 1 these two tasks were performed in sequence; in Experiment 2 they were separated into three experimental blocks to rule out the possibility that readers strategically formed auditory imagery as a result of task demands. In both studies, readers were faster to correctly categorize sounds as ‘real’ when the sounds had been implied by a preceding sentence. These results suggest that readers mentally simulate the implied auditory characteristics of sentences, even in the absence of tasks that promote mental simulation. Mentally simulating described events is not limited to visual and action-based modalities, further demonstrating the multimodal nature of the perceptual symbols spontaneously activated during reading.     

Sequence effects in categorization of simple perceptual stimuli

Categorization research typically assumes that the cognitive system has access to a (more or less noisy) representation of the absolute magnitudes of the properties of stimuli and that this information is used in reaching a categorization decision. However, research on identification of simple perceptual stimuli suggests that people have very poor representations of absolute magnitude information and that judgments about absolute magnitude are strongly influenced by preceding material. The experiments presented here investigate such sequence effects in categorization tasks. Strong sequence effects were found. Classification of a borderline stimulus was more accurate when preceded by a distant member of the opposite category than by a distant member of the same category. It is argued that this category contrast effect cannot be accounted for by extant exemplar or decision-bound models of categorization. The effect suggests the use of relative magnitude information in categorization. A memory and contrast model illustrates how relative magnitude information may be used in categorization.     

Metacognitive components of visual search in children

Two studies examined children's increasing ability to analyze tasks in terms of the perceptual features that affect task difficulty. Of particular interest was any understanding that perceptual confusions occur during the search for an object surrounded by objects similar in shape or color to that object. In Study 1, 32 pre-schoolers constructed arrays intended to make the search easy or difficult. They made the search difficult simply by putting many toys into the toy box. In a forced-choice situation, they indicated that task difficulty was influenced by the number of objects and the similarity in color and shape of the targets and the surrounding objects. Study 2 more thoroughly examined knowledge of color and shape confusions, using 96 children from Grades K, 1, 3, and 4, assigned to two age groups. The older children but not the younger ones showed a significant understanding of color and shape confusions. Both age groups understood that performance is affected by a person's interest level and degree of attention to the task. The results were discussed in terms of the accessibility of the children's knowledge under different conditions.     

Dr. Angry and Mr. Smile: when categorization flexibly modifies the perception of faces in rapid visual presentations

Are categorization and visual processing independent, with categorization operating late, on an already perceived input, or are they intertwined, with the act of categorization flexibly changing (i.e. cognitively penetrating) the early perception of the stimulus? We examined this issue in three experiments by applying different categorization tasks (gender, expressive or not, which expression and identity) to identical face stimuli. Stimuli were hybrids: they combined a man or a woman with a particular expression at a coarse spatial scale with a face of the opposite gender with a different expression at the fine spatial scale. Results suggested that the categorization task changes the spatial scales preferentially used and perceived for rapid recognition. A perceptual set effect is shown whereby the scale preference of an important categorization (e.g. identity) transfers to resolve other face categorizations (e.g. expressive or not, which expression). Together, the results suggest that categorization can be closely bound to perception.     

True or false: do 5-year-olds understand belief?

In 3 studies (N = 188) we tested the hypothesis that children use a perceptual access approach to reason about mental states before they understand beliefs. The perceptual access hypothesis predicts a U-shaped developmental pattern of performance in true belief tasks, in which 3-year-olds who reason about reality should succeed, 4- to 5-year-olds who use perceptual access reasoning should fail, and older children who use belief reasoning should succeed. The results of Study 1 revealed the predicted pattern in 2 different true belief tasks. The results of Study 2 disconfirmed several alternate explanations based on possible pragmatic and inhibitory demands of the true belief tasks. In Study 3, we compared 2 methods of classifying individuals according to which 1 of the 3 reasoning strategies (reality reasoning, perceptual access reasoning, belief reasoning) they used. The 2 methods gave converging results. Both methods indicated that the majority of children used the same approach across tasks and that it was not until after 6 years of age that most children reasoned about beliefs. We conclude that because most prior studies have failed to detect young children's use of perceptual access reasoning, they have overestimated their understanding of false beliefs. We outline several theoretical implications that follow from the perceptual access hypothesis.     

Global influences on the development of spatial and object perceptual categorization abilities: Evidence from preterm infants

Influences on the development of perceptual categorization were examined by comparing the performance of three groups of infants on spatial and object categorization tasks. The groups consisted of 1) fullterm infants tested at 3 to 4 months of age, 2) healthy preterm infants tested 3 to 4 months from birth (postnatals), and 3) healthy preterm infants tested 3 to 4 months from their due date (postterms). Four experiments showed that fullterms and postterms outperformed postnatals on a spatial categorization task (i.e., ‘above’ vs. ‘below’, and that fullterms outperformed both postnatals and postterms on object categorization tasks (i.e., dogs vs. cats, and cats vs. birds). These results suggest that maturation may be the predominant influence on the early development of the ability to form categorical representations of spatial information, while preterm birth may exert a limiting influence on the development of object categorization abilities.     

Declarative strategies persist under increased cognitive load

When humans simultaneously execute multiple tasks, performance on individual tasks suffers. Complementing existing theories, this article poses a novel question to investigate interactions between memory systems supporting multi-tasking performance: When a primary and dual task both recruit declarative learning and memory systems, does simultaneous performance of both tasks impair primary task performance because learning in the declarative system is reduced, or because control of the primary task is passed to slower procedural systems? To address this question, participants were trained on either a perceptual categorization task believed to rely on procedural learning or one of three different categorization tasks believed to rely on declarative learning. Task performance was examined with and without a simultaneous dual task thought to recruit working memory and executive attention. To test whether the categories were learned procedurally or declaratively, the response keys were switched after a learning criterion had been reached. Large impairments in performance after switching the response keys are taken to indicate procedural learning, and small impairments are taken to indicate declarative learning. Our results suggest that the declarative memory categorization tasks (regardless of task difficulty) were learned by declarative systems, regardless of whether they were learned under dual-task conditions.