Categorical Perception

In previous experiments two extreme modes of visual discrimination performance have been investigated by measuring small differences in pattern shape at points along a continuum of pattern shapes. These two modes, associated with discrete and continuous encoding processes, were obtained by simultaneously manipulating the number of pattern components in the display and the effective duration of the display. In this experiment, discrimination performance was measured for a fixed number of pattern components, namely three, and variable display time course. The stimuli used were curved lines drawn from a continuum with curvature parameter s. There were three stimulus time courses: (1) 2-s stimulus display, (2) 100-ms stimulus display, and (3) 100-ms stimulus display followed by a post-stimulus mask. Discrimination performance declined smoothly and monotonically with s for (1), but varied non-monotonically with s revealing a central peak for (3). Performance for (2) was intermediate between that for (1) and that for (3). A reduction in effective stimulus duration alone was thus sufficient to cause a transition from continuous to discrete modes of discrimination performance, a result which may be compatible with an explanation of variable discrimination modes based on a method of successive internal approximations of the stimulus.

The demands of social life often require categorically judging whether someone's continuously varying facial movements express "calm" or "fear," or whether one's fluctuating internal states mean one feels "good" or "bad." In two studies, we asked whether this kind of categorical, "black and white," thinking can shape the perception and neural representation of emotion. Using psychometric and neuroimaging methods, we found that (a) across participants, judging emotions using a categorical, "black and white" scale relative to judging emotions using a continuous, "shades of gray," scale shifted subjective emotion perception thresholds; (b) these shifts corresponded with activity in brain regions previously associated with affective responding (i.e., the amygdala and ventral anterior insula); and (c) connectivity of these regions with the medial prefrontal cortex correlated with the magnitude of categorization...

Perceptually categorizing a face to its racial belonging may have important consequences on interacting with people. However, race categorical perception (CP) has been scarcely investigated nor its developmental pathway. In this study, we tested the neurolinguistics rewiring hypothesis, stating that language acquisition modulates the brain processing of social perceptual categories. Accordingly, we investigated the electrophysiological correlates of race CP in a group of adults and children between 3 and 5 years of age. For both groups we found a greater modulation of the N400 connected with the processing of between category boundaries (i.e., faces belonging to different race groups) than withincategory boundaries (i.e., different faces belonging to the same race group). This effect was the same in both adults and children, as shown by the comparable between-group amplitude of the differential wave (DW) elicited by the between-category faces. Remarkably, this effect was positively correlated with racial-labels acquisition, but not with age, in children. Finally, brain source analysis revealed the activation of a more modularized cortical network in adults than in children, with unique activation of the left superior temporal gyrus (STG) and the inferior frontal gyrus (IFG), which are areas connected to language processing. These are the first results accounting for an effect of language in rewiring brain connectedness when processing racial categories.

The alveolar-retroflex contrast is a critical feature in Mandarin and is often used to differentiate Beijing Mandarin from other dialects of Mandarin like Taiwan Mandarin. While a number of linguistic and sociolinguistic factors have been found to affect the alveolar-retroflex contrast, leading to variation in Taiwan Mandarin, a consistent alveolar-retroflex distinction is described for Beijing Mandarin in the literature on Mandarin phonology. With a series of map tasks, this dissertation examines whether the production of alveolar-retroflex contrast in both dialects is subject to the effects of vowel context and focal prominence. With a discrimination task and a goodness rating task, the categorical and gradient modes of alveolar-retroflex perception in different vowel contexts are investigated for listeners of both dialects. Results of the production study indicate that the acoustic characterization of Beijing vs. Taiwan Mandarin alveolarretroflex contrast varies by vowel and by how each contrasting phoneme is realized in a particular vowel context. Focal prominence is found to result in longer syllable durations but not increased spectral distinctiveness between the alveolar and retroflex sibilants. The findings are discussed with respect to enhancement theory. The perception study found that Beijing and Taiwan listeners have different perceptual boundaries along the acoustic continuum, with a lower cutoff frication frequency required for the retroflex percepts for Beijing listeners. Listeners' alveolar-retroflex boundaries shift to lower frequencies in the rounded vowel context to normalize for vowel coarticulatory effects. Discrepant within-category sensitivity was found in that while both Beijing and Taiwan listeners perceive all retroflex variants as equally good, Beijing listeners consider the endpoint variant of the alveolar as the best category exemplar. The findings are discussed within the frameworks of quantal theory and exemplar theory as well as with respect to the hyperspace effect in perception. Together, the results show that linguistic (i.e., iii vowel context) and sociolinguistic (i.e., dialect) factors collectively and variably affect the production and perception of the Mandarin alveolar-retroflex contrast.

Anxiety has been associated with a bias for interpreting threatening information. Faces expressing anger seem to be more easily detected by socially anxious individuals than by non-anxious individuals. Similarly, disgust on a face may also reflect a negative social judgment. We tested the hypothesis that individuals displaying non-clinical social anxiety would be as sensitive to disgust as to anger interpretation by comparing individuals scoring high or low on the fear of social evaluation scale (FNE, Watson and Friend, 1969). Eventrelated potentials (ERP) were recorded in response to repetitions of a particular facial expression (e.g. anger) and in response to two deviating (rare) stimuli obtained by a morphing procedure, where one depicted the same emotion as the frequent stimulus, while the other depicted a different facial expression (e.g. disgust). The classic effect of categorical perception was reproduced: at a behavioral level, people detected more easily rare faces depicting a different emotion than faces depicting the same emotion. ERP results suggest that deviant faces depicting a different emotion evoked an earlier attentional N2b/P3a wave complex, together with an earlier and enhanced P3b. More interestingly, participants with non-clinical social anxiety manifested a reduced N2b wave when they had to detect a change in intensity of anger presentation. However, these individuals did not show facilitation to disengage from disgust when they have to detect angry faces, which was displayed by control participants. Implications and suggestions for further research about the role played by anger and disgust in psychopathology are outlined.

Pitch is the psychological correlate of the fundamental frequency and is important for speech perception. The quality of the sound is dependent on the highness or lowness of tone pitch along with other acoustic cues. It is a major cue for the identification of suprasegmental aspects of speech; helpful in gender identification; age identification; emotional arousal; cultural variations; and sociocultural aspects. The change in pitch does not vary the meaning of spoken words or sentences in most of the Indo-European languages such as English, Hindi, and Sanskrit, but in Sino-Tibetan languages such as Mandarin, Cantonese, and Thai, the change in the pitch contours changes the meaning of the words. Such languages where the meaning of the words is dependent on the pitch contour within a syllable are known as tonal languages. Perception of pitch is a topic of scientific enquiry. The contour tone of pitch is perceived categorically. The categorical perception indicates that the gradually morphed stimulus is perceived as discrete identities in the auditory system. Thus, the pitch perception is categorical when the continuum involves the change in the direction of the pitch contour. In the last decade, a surge of interest has been developed to assess the pitch contour contrasts of tonal languages. Mandarin Chinese is one such tonal language involving contour tones which is perceived categorically. Researchers reported strong evidences of categorical perception for pitch contrasts in Mandarin, Thai, and Cantonese listeners. Xi et al. have found that categorical perception of lexical tones in Mandarin Chinese is perceived categorically.

Recent research indicates that adults show categorical perception of facial expressions of emotion. It is not known whether this is a basic characteristic of perception that is present from the earliest weeks of life, or whether it is one that emerges more gradually with experience in perceiving and interpreting expressions. We report two experiments designed to investigate whether young infants, like adults, show categorical perception of facial expressions. 7-month-old infants were shown photographic quality continua of interpolated (morphed) facial expressions derived from two prototypes of fear and happiness. In the first experiment, we used a visualpreference technique to identify the infants' category boundary between happiness and fear. In the second experiment, we used a combined familiarisation ^visual-preference technique to compare infants' discrimination of pairs of expressions that were equally physically different but that did or did not cross the emotion-category boundary. The results suggest that 7-month-old infants (i) show evidence of categorical perception of facial expressions of emotion, and (ii) show persistent interest in looking at fearful expressions.

ABSTRACTWe intended to establish if two lexical tone contrasts in Zhumadian Mandarin, one between early and late aligned falls and another between early and late aligned rises, are perceived categorically, while the difference between declarative and interrogative pronunciations of these four tones is perceived gradiently. Presenting stimuli from 7-point acoustic continua between tones and between intonations, we used an identification task and a discrimination task with an experimental group of native listeners and a control group of Indonesian listeners, whose language employs none of the differences within either the falling or the rising pitch contours in its phonology. Only the lexical condition as perceived by the experimental group yielded sigmoid identification functions and a heightened discriminatory sensitivity around the midpoint of continua. The intonational condition in the native group and both conditions in the control group yielded gradient identification functions ...

We can perceive small color differences, and we can also perceive color as a group of many different colors (categorical color perception) . Visual performances based on small color differences are known to be better in the central visual field than in the periphery. We have clarified the characteristics of categorical color perception in the peripheral visual field . Observers were shown color chips of the OSA Uniform Color Scales set in the central or the peripheral visual field. The chip, which subtended 4deg, was presented at the fovea (Odeg), eccentricities of 30 , 50, and 60 deg in the nasal visual field and of 30, 50, 70, 80, and 90 deg in the temporal visual field. A large gray surrounding field was made with a hemisphere and illuminated at a moderate intensity of D65 lights (yielding 2000 scotopic td) to suppress rod activity . The observers reported color appearance of the stimulus with one of the eleven basic color terms. The distributions of the color categories on the xy chromaticity diagram varied little between stimulus locations from 30 deg to the nasal and 70 deg to the temporal visual field. The results of eccentricities greater than nasal 50 deg and temporal 80 deg were remarkable different from those in the locations closer to the fovea. Our results suggest that categorical color perception in the central visual field is maintained across a wide area of the peripheral visual field.

Language is often regarded as a rich source of evidence about the mind. However, a number of findings challenge this position, at least at the level of words: Where languages differ in their lexical distinctions, conceptual differences are not always observed. We ask here how language might serve as a window into the mind despite an apparently loose connection between words and concepts. We propose that prominent conceptual distinctions, though not necessarily captured by individual words, may be revealed by elements of meaning shared by multiple words. Testing this hypothesis in the domain of space, we show that clusters of spatial terms, identified through dimensionality reduction analyses of semantic similarity data, align with conceptual categories spontaneously accessed during the perceptual discrimination of spatial relations. These findings suggest that aspects of semantic structure beyond the level of words may provide considerable insight into the conceptual system. Implications for research on linguistic relativity are discussed.

Previous research has demonstrated that listeners make use of both auditory and visual information in bimodal speech perception. Preschool children appear to evaluate and integrate the two sources of information in the same manner as adults, but the children are less influenced by the visual source. The current experiments test a possible explanation of this difference and extend the question to younger children. It is possible that children are poorer lip-readers than adults and thus have less complete information about the visual source. Children and adults were tested with both auditory and visual sources and were also required to identify speech events on the basis of only the visual source. In addition to replicating the previous findings in the bimodal situation, the current experiments found that children are poorer lip-readers than adults. Furthermore, a positive correlation was observed between lipreading ability and the size of the visual contribution to bimodal speech perception. A fuzzy logical model of speech perception provided a good quantitative description of the results even with the assumption that the visual information was equivalent in both the bimodal and lipreading conditions. The results also contradict the categorical perception of speech events and any nonindependence in the evaluation of auditory and visual information in speech perception. 0 1986 Academic PWS. Inc.

The magnification exponents μ occurring in adaptive map formation algorithms like Kohonen's self-organizing feature map deviate for the information theoretically optimal value μ = 1 as well as from the values that optimize, e.g., the mean square distortion error (μ = 1/3 for one-dimensional maps). At the same time, models for categorical perception such as the "perceptual magnet" effect, which are based on topographic maps, require negative magnification exponents μ < 0. We present an extension of the self-organizing feature map algorithm, which utilizes adaptive local learning step sizes to actually control the magnification properties of the map. By change of a single parameter, maps with optimal information transfer, with various minimal reconstruction errors, or with an inverted magnification can be generated. Analytic results on this new algorithm are complemented by numerical simulations.

In this paper we describe a type of neuron of the medial premotor cortex (MPC) that discharged differentially during a categorization task and reflected in their activity whether the speed of a tactile stimulus was low or high. The activity of these neurons was recorded in the MPC contralateral (right MPC, n = 88) and ipsilateral (left MPC, n = 103) to the stimulated hand of four monkeys performing this somesthetic task. Animals performed the task by pressing with the right hand one of two target switches to indicate whether the speed of probe movement across the skin of the left hand was low or high. Differential responses of MPC neurons occurred during the stimulus and reaction time period. We used an analysis based on signal detection theory to determine whether these differential responses were associated with the animal's decision. According to this analysis, 104 of the 191 neurons (right MPC, n = 48; left MPC, n = 56) coded the categorization of the stimulus speeds (categorical neurons). In a light instruction task, we tested the possibility that the categorical neurons (n = 71) were associated with the intention to press, or with the trajectory of the hand to one of the two target switches used to indicate categorization. In this situation, each trial began as in the somesthetic categorization task, but one of the two target switches was illuminated beginning with the skin indentation, continued during the delay period and turned off when the probe was lifted off from the skin. This condition instructed the animal which target switch was required to be pressed for reward. Very few neurons (14 of 71) maintained their differential responses observed in the categorization task. Some categorical neurons (n = 6) were also studied; the animal categorized the tactile stimulus speeds, but knew in advance whether the stimulus speed was low or high (categorization + light instruction). This was made by illuminating one of the two target switches which was associated with the stimulus speed. The categorical response was considerably attenuated in this condition. Interestingly, during the delay period, these neurons reflected in their activity whether the stimulus was low or high. A number of the categorical MPC neurons (n = 30) were studied when the same set of stimuli, used in the categorization, were delivered passively. None of these neurons responded in this condition. These results suggest that the MPC, apart from its well-known role in motor behavior, is also involved in the animal's decision during the execution of this learned somesthetic task.

We study the dynamic categorization ability of an autonomous agent that distinguishes rectangular and triangular objects. The objects are distributed on a two-dimensional space and the agent is equipped with a recurrent neural network that controls its navigation dynamics. As the agent moves through the environment, it develops neural states which, while not symbolic representations of rectangles or triangles, allow it to distinguish these objects. As a result, it decides to avoid triangles and remain for longer periods of time at rectangles. A significant characteristic of the network is its plasticity, which enables the agent to switch from one navigation mode to another. Diversity of this switching behavior will be discussed.

Efficient speech perception requires the mapping of highly variable acoustic signals to distinct phonetic categories. How the brain overcomes this many-to-one mapping problem has remained unresolved. To infer the cortical location, latency, and dependency on attention of categorical speech sound representations in the human brain, we measured stimulus-specific adaptation of neuromagnetic responses to sounds from a phonetic continuum. The participants attended to the sounds while performing a non-phonetic listening task and, in a separate recording condition, ignored the sounds while watching a silent film. Neural adaptation indicative of phoneme category selectivity was found only during the attentive condition in the pars opercularis (POp) of the left inferior frontal gyrus, where the degree of selectivity correlated with the ability of the participants to categorize the phonetic stimuli. Importantly, these category-specific representations were activated at an early latency of 115-140 ms, which is compatible with the speed of perceptual phonetic categorization. Further, concurrent functional connectivity was observed between POp and posterior auditory cortical areas. These novel findings suggest that when humans attend to speech, the left POp mediates phonetic categorization through integration of auditory and motor information via the dorsal auditory stream.

Efficient speech perception requires the mapping of highly variable acoustic signals to distinct phonetic categories. How the brain overcomes this many-to-one mapping problem has remained unresolved. To infer the cortical location, latency, and dependency on attention of categorical speech sound representations in the human brain, we measured stimulus-specific adaptation of neuromagnetic responses to sounds from a phonetic continuum. The participants attended to the sounds while performing a non-phonetic listening task and, in a separate recording condition, ignored the sounds while watching a silent film. Neural adaptation indicative of phoneme category selectivity was found only during the attentive condition in the pars opercularis (POp) of the left inferior frontal gyrus, where the degree of selectivity correlated with the ability of the participants to categorize the phonetic stimuli. Importantly, these category-specific representations were activated at an early latency of 115...

The question of whether language affects perception has been debated largely on the basis of cross-language data, without considering the functional organization of the brain. The nature of this neural organization predicts that, if language affects perception, it should do so more in the right visual field than in the left visual field, an idea unexamined in the debate. Here, we find support for this proposal in lateralized color discrimination tasks. Reaction times to targets in the right visual field were faster when the target and distractor colors had different names; in contrast, reaction times to targets in the left visual field were not affected by the names of the target and distractor colors. Moreover, this pattern was disrupted when participants performed a secondary task that engaged verbal working memory but not a task making comparable demands on spatial working memory. It appears that people view the right (but not the left) half of their visual world through the lens...

This paper investigates the contextual recognition of neutral thirds in music by integrating real-world musical context into the study of categorical perception. Traditionally, categorical perception has been studied using isolated auditory stimuli in controlled laboratory settings. However, music is typically experienced within a circumstantial framework, significantly influencing its reception. Our study involved musicians from various specializations who listened to precomposed musical fragments, each concluding with a 350-cent interval preceded by different harmonic contexts. The fragments included a monophonic synthesizer and orchestral mockups, with contexts such as major chords, minor chords, a single pitch, neutral thirds, and natural fifths. The results indicate that musical context remarkably affects the recognition of pseudotonal chords. Participants' accuracy in judging interval size varied based on the preceding harmonic context. Two statistical analyses was conducted to determine if there were significant differences in the neutral third perception across the different harmonic contexts (p = 9.86*10^-29) and across the cultural background of the study participants (p = 0.8998). The findings underscore the need to consider real-world listening experiences in research on auditory processing and cognition.

This article considers categorical perception (CP) as a crucial process involved in all sort of communication throughout the biological hierarchy, i.e. in all of biosemiosis. Until now, there has been consideration of CP exclusively within the functional cycle of perception-cognition-action and it has not been considered the possibility to extend this kind of phenomena to the mere physiological level. To generalise the notion of CP in this sense, I have proposed to distinguish between categorical perception (CP) and categorical sensing (CS) in order to extend the CP framework to all communication processes in living systems, including intracellular, intercellular, metabolic, physiological, cognitive and ecological levels. The main idea is to provide an account that considers the heterarchical embeddedness of many instances of CP and CS. This will take me to relate the hierarchical nature of categorical sensing and perception with the equally hierarchical issues of the "binding problem", "triadic causality", the "emergent interpretant" and the increasing semiotic freedom observed in biological and cognitive systems.

The division of continuously variable acoustic signals into discrete perceptual categories is a fundamental feature of vocal communication, including human speech. Despite the importance of categorical perception to learned vocal communication, the neural correlates underlying this phenomenon await identification. Here we report that individual sensorimotor neurons in freely behaving swamp sparrows express categorical auditory responses to changes in note duration, a learned feature of their songs, and that the neural response boundary accurately predicts the categorical perceptual boundary measured in field studies of the same sparrow population. Furthermore, swamp sparrow populations that learn different song dialects exhibit different categorical perceptual boundaries, consistent with the boundary being learned. Our results extend the analysis of the neural basis of perceptual categorization into the realm of vocal communication, while advancing the learned vocalizations of songbirds as a model for investigating how experience shapes categorical perception and the activity of categorically responsive neurons. Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

IntroductionProcessing the wealth of sensory information from the surrounding environment is a vital human function with the potential to develop learning, advance social interactions, and promote safety and well-being.MethodsTo elucidate underlying processes governing these activities we measured neurophysiological responses to patterned stimulus sequences during a sound categorization task to evaluate attention effects on implicit learning, sound categorization, and speech perception. Using a unique experimental design, we uncoupled conceptual categorical effects from stimulus-specific effects by presenting categorical stimulus tokens that did not physically repeat.ResultsWe found effects of implicit learning, categorical habituation, and a speech perception bias when the sounds were attended, and the listeners performed a categorization task (task-relevant). In contrast, there was no evidence of a speech perception bias, implicit learning of the structured sound sequence, or repe...

& Where and how does the brain discriminate familiar and unfamiliar faces? This question has not been answered yet by neuroimaging studies partly because different tasks were performed on familiar and unfamiliar faces, or because familiar faces were associated with semantic and lexical information. Here eight subjects were trained during 3 days with a set of 30 faces. The familiarized faces were morphed with unfamiliar faces. Presented with continua of unfamiliar and familiar faces in a pilot experiment, a group of eight subjects presented a categorical perception of face familiarity: there was a sharp boundary in percentage of familiarity decisions between 40% and 60% faces. In the main experiment, subjects were scanned (PET) on the fourth day (after 3 days of training) in six conditions, all requiring a sex classification task. Completely novel faces (0%) were presented in Condition 1 and familiar faces (100%) in Condition 6, while faces of steps of 20% in the continuum of familiarity were presented in Conditions 2 to 5 (20% to 80%). A principal component analysis (PCA) indicated that most variations in neural responses were related to the dissociation between faces perceived as familiar (60% to 100%) and faces perceived as unfamiliar (0 to 40%). Subtraction analyses did not disclose any increase of activation for faces perceived as familiar while there were large relative increases for faces perceived as unfamiliar in several regions of the right occipito-temporal visual pathway. These changes were all categorical and were observed mainly in the right middle occipital gyrus, the right posterior fusiform gyrus, and the right inferotemporal cortex. These results show that (1) the discrimination between familiar and unfamiliar faces is related to relative increases in the right ventral pathway to unfamiliar/ novel faces; (2) familiar and unfamiliar faces are discriminated in an all-or-none fashion rather than proportionally to their resemblance to stored representations; and (3) categorical perception of faces is associated with abrupt changes of brain activity in the regions that discriminate the two extremes of the multidimensional continuum. &

Drawing on data from interviews with mathematics faculty in three different types of undergraduate institutions and using Rabardel's model of instrument use (Vérillon & Rabardel 1995), we describe three ways textbooks mediate college faculty work regarding instruction. The model anticipates epistemic and pragmatic mediations between the instructor and teaching, others, and self, with the textbook playing a significant role. We provide illustrations of each of these mediations as described by the participants. Pragmatic rather than epistemic mediations were more common. In addition, we found that the mediations seem largely dependent on instructors' categorical perceptions of their students, either as "math students" or as "undergraduate students". These alternate perceptions resulted in different descriptions of schemas for using the textbook with each type of student. The analysis generates further questions for research regarding either a developmental component or a curricular component that could explain this categorization of students. Keywords Textbook mediation. College level. Mathematics instructors. Textbook use. Tertiary level Textbooks appear to be a predominant feature in the teaching of tertiary mathematics, but the phenomenon of instructor-textbook use in higher education has not been extensively studied. We wanted to know how textbooks are being used and what faculty's reasons behind those uses are. We had three reasons for pursuing these questions. First, in the USA, there have been calls for changing instruction in undergraduate mathematics to promote greater student engagement with the material and heavier use of technology, especially in the first 2 years (Blair, 2006; Steen, 1998). In order to support such changes, new textbooks

This paper investigates respiratory odor navigation with minimal evolutionary robots. We introduce a novel agent tasked with locating a chemical source solely through the use of a respiratory sensor, a challenge inspired by the active sampling strategies observed in a wide variety of animals (e.g., sniffing, whisking). Prevailing hypotheses suggest that odor navigation serves predominantly to gate behaviors in response to information gleaned from different sensory modalities. We analyze the agent's behavior and neural dynamics using dynamical systems theory, demonstrating the possibility of strategies that instead rely solely on the information obtained from their respiratory sensor. Our findings reveal that agents can successfully locate chemical sources through the synchronization of breathing rates with motor outputs, mirroring sensorimotor coupling strategies recently identified in the experimental literature. This research contributes to the theoretical understanding of sensory odor navigation and the role of physiology in agent-environment interactions.

We review research on the neural correlates of colour categories, and categorical responses in preverbal infants and animals. Our aim was to address the question of the functional segregation of colour categories from colour perception and colour language, i.e. whether or not colour categorisation shares processing resources with language and perception. Together, the reviewed findings suggest that colour categorisation often involves automatic language processing, but it can also occur in the absence of language or colour naming, as suggested by research on brain-damaged patients, preverbal infants, and non-human animals. Furthermore, there is no compelling evidence coming from human neuroimaging and neuropsychological studies, or from animal studies, that categorisation is inherent to colour perception. Instead, colour categorisation might simply build upon the continuous perception of colour and may interact with perception through the direction of attention to colour differences that are relevant to categorisation. Altogether, the reviewed evidence does not seem to offer a straightforward account of the origin of lexical colour categories. We suggest that future research in all areas (1) requires methodological improvements, in particular in stimulus control, (2) should overcome the universalist-realist debate and go beyond a simple contrast between perception and language, and (3) should consider the link between object colours and colour categories to establish both evolutionary and developmental continuity between categorical responses in animals, infants and adult humans.

The 'simulation hypothesis' is an intriguing explanation for cognition, and holds that 'thinking consists of simulated interaction with the environment' ([4], p.242). However, the neuroscientific proof for a simulation mechanism in the brain is indirect. In this paper we present a minimal-model approach to investigate the 'simulation hypothesis'. Our minimal model is called ACP and is an extension of the Active Categorical Perception model (ACP) presented in . In ACP , robots have a neurocontroller with an output-input feedback mechanism that allows them to simulate perception and behaviour internally. Our experiments focus on the performance of robots with three different types of neurocontroller (two feedforward and one recurrent type of neurocontroller). Their performance is compared over three experimental conditions in which the output-input feedback mechanism is functional for variable durations. The results show that feedforward-neurocontrolled robots benefit from output-input feedback, while recurrent-neurocontrolled robots do not. Based on these results, two closely related conclusions are drawn: (1) the 'simulation hypothesis' may be too specific, and (2) predicting future perception may depend on neural recurrency (i.e., internal feedback) in general, rather than on the ability to simulate perception by feeding back actions.

Among the five senses, vision and audition share very strong anatomical, functional, and cognitive links. This is especially true for speech perception. Visual speech (ie speech reading) influences auditory perception at the very early stages of audiovisual speech processing [1]. This ...

Several theoretical models predict that nonnative speech discrimination depends on phonetic fit as well as phonological correspondence to native phonemes. Languages differ both phonologically and phonetically, e.g., high vowels differ among English, French, Danish, Norwegian. All use /i u/, all except English use /y/, but only Norwegian has / /. These languages realize /i y u/ differently. American, Danish and French listeners categorized and discriminated Norwegian /i/-/y/, /y/-/u/, /y/-/ /, / /-/u/. Danes assimilated the first three to native contrasts, / /-/u/ as an /y/ goodness difference, and discriminated all near ceiling. French listeners assimilated /y/-/u/, /y/-/ /, / -u/ to native contrasts, Americans assimilated /y/-/u/ and /y/-/ / to native contrasts, / -u/ to allophones of native /u/. They discriminated those contrasts near ceiling. French listeners assimilated /i/-/y/ as an /i/ goodness difference, discriminating it worse than Danes but better than Americans, who assim...

Previous work has not yielded clear conclusions about the categorical nature of perception of tone contrasts by native listeners of tone languages. We reopen this issue in a cross-linguistic study comparing Taiwan Mandarin and French listeners. We tested these listeners on three tone continua derived from natural Mandarin utterances within carrier sentences, created via a state-of-the-art pitch-scaling technique in which within-continuum interpolation was applied to both f 0 and intensity contours. Classic assessments of categorization and discrimination of each tone continuum were conducted with both groups of listeners. In Experiment 1, Taiwanese listeners identified the tone of target syllables within carrier sentence context and discriminated tones of single syllables. In Experiment 2, both French and Taiwanese listeners completed an AXB identification task on single syllables. Finally, French listeners were run on an AXB discrimination task in Experiment 3. Results indicated that Taiwanese listeners' perception of tones is quasi-categorical whereas French listeners' is psychophysically based. French listeners nevertheless show substantial sensitivity to tone contour differences, though to a lesser extent than Taiwanese listeners. Thus, the findings suggest that despite the lack of lexical tone contrasts in the French language, French listeners are not absolutely ''deaf'' to tonal variations. They simply fail to perceive tones along the lines of a welldefined and finite set of linguistic categories.

Surrounding context influences speech listening, resulting in dynamic shifts to category percepts. To examine its neural basis, event-related potentials (ERPs) were recorded during vowel identification with continua presented in random, forward, and backward orders to induce perceptual warping. Behaviorally, sequential order shifted individual listeners’ categorical boundary, versus random delivery, revealing perceptual warping (biasing) of the heard phonetic category dependent on recent stimulus history. ERPs revealed later (∼300 ms) activity localized to superior temporal and middle/inferior frontal gyri that predicted listeners’ hysteresis/enhanced contrast magnitudes. Findings demonstrate that interactions between frontotemporal brain regions govern top-down, stimulus history effects on speech categorization.

Ž. Event-related Fields ERFs were recorded in eleven normal volunteers in response to four two-tone stimuli selected from a tone onset Ž. time TOT continuum. The latter has been used extensively in the past as an analog of voice onset-time, an important cue for making Ž < < < <. Ž voicing distinctions e.g., pa versus ba. TOT values ranged from 0 to 60 ms in 20-ms steps. Three components of the ERF P50m,. N1m, and P2m in the hemisphere contralateral to the stimulated ear were analyzed. The most significant finding was an abrupt reduction Ž. in the peak field amplitude of N1m bilaterally as TOT values increased from q20 to q40 ms. No systematic differences were noted between the 0 and q20 ms stimuli or between the q40 and q60 ms tokens. On the other hand, peak component latencies rose steadily with increasing TOT values. The discontinuity in the change of peak RMS as a function of TOT is in close agreement with behavioral evidence of categorical perception of similar non-speech as well as speech stimuli. q 1998 Elsevier Science B.V.

There have been controversial debates across multiple disciplines regarding the underlying mechanism of developmental stuttering. Stuttering is often related to issues in the speech production system; however, the presence and extent of a speech perception deficit is less clear. This study aimed to investigate the speech perception of children who stutter (CWS) using the categorical perception paradigm to examine their ability to categorize different acoustic variations of speech sounds into the same or different phonemic categories. In this study, 15 CWS and 16 children who do not stutter (CWNS) completed identification and discrimination tasks involving acoustic variations of Cantonese speech sounds in three stimulus contexts: consonants (voice onset times, VOTs), lexical tones, and vowels. The results showed similar categorical perception performance in boundary position and width in the identification task and similar d' scores in the discrimination task between the CWS and CWNS groups. However, the reaction times (RTs) were slower in the CWS group compared with the CWNS group in both tasks. Moreover, the CWS group had slower RTs in identifying stimuli located across categorical boundaries compared with stimuli located away from categorical boundaries. Overall, the data implied that the phoneme representation evaluated in speech perception might be intact in CWS as revealed by similar patterns in categorical perception as those in CWNS. However, the CWS group had slower processing speeds during categorical perception, which may indicate an insufficiency in accessing the phonemic representations in a timely manner, especially when the acoustic stimuli were ambiguous.

Congenital amusia is a lifelong disorder of fine-grained pitch processing in music and speech. However, it remains unclear whether amusia is a pitch-specific deficit, or whether it affects frequency/spectral processing more broadly, such as the perception of formant frequency in vowels, apart from pitch. In this study, in order to illuminate the scope of the deficits, we compared the performance of 15 Cantonese-speaking amusics and 15 matched controls on the categorical perception of sound continua in four stimulus contexts: lexical tone, pure tone, vowel, and voice onset time (VOT). Whereas lexical tone, pure tone and vowel continua rely on frequency/spectral processing, the VOT continuum depends on duration/temporal processing. We found that the amusic participants performed similarly to controls in all stimulus contexts in the identification, in terms of the across-category boundary location and boundary width. However, the amusic participants performed systematically worse than controls in discriminating stimuli in those three contexts that depended on frequency/spectral processing (lexical tone, pure tone and vowel), whereas they performed normally when discriminating duration differences (VOT). These findings suggest that the deficit of amusia is probably not pitch specific, but affects frequency/spectral processing more broadly. Furthermore, there appeared to be differences in the impairment of frequency/spectral discrimination in speech and nonspeech contexts. The amusic participants exhibited less benefit in between-category discriminations than controls in speech contexts (lexical tone and vowel), suggesting reduced categorical perception; on the other hand, they performed inferiorly compared to controls across the board regardless of between-and within-category discriminations in nonspeech contexts (pure tone), suggesting impaired general auditory processing. These differences imply that the frequency/spectralprocessing deficit might be manifested differentially in speech and nonspeech contexts in amusics-it is manifested as a deficit of higher-level phonological processing in speech sounds, and as a deficit of lower-level auditory processing in nonspeech sounds.

This paper investigates if individuals with amusia show deficits in the identification and discrimination of Mandarin vowels, with the aim of exploring whether the deficiency of the amusics lies in the acoustic processing of frequency, or in pitch processing. The results showed that the amusics performed comparably as the controls in vowel identification. For discrimination, both groups exhibited better discrimination for between-category pairs than within-category pairs, indicating that the amusics are not impaired in the categorical perception of vowels. However, amusics exhibited poorer accuracy than the controls in vowel discrimination across the board, irrespective of between-or within-category vowel pairs. Moreover, the participants' vowel discrimination accuracy is significantly correlated to their musical ability, as indexed by the Montreal Battery of Evaluation of Amusia (MBEA) scores. The results suggest that individuals with congenital amusia might be impaired in frequency processing in general, a deficiency broader than originally believed.

This study investigated both production and perception of Mandarin speech, comparing two groups of 4-to-5-year-old children, a normal-hearing (NH) group and a cochlearimplanted (CI) hearing-impaired group; the perception ability of the CI group was tested under two conditions, with and without hearing aids. In the production study, the participants were asked to produce sustained vowels /a/, /i/ and /u/, on which a set of acoustic parameters were then measured. In comparison to the NH group, the CI group showed a higher F0, a higher H1-H2, and a smaller acoustic space for vowels, demonstrating both phonatory and articulatory impairments. In the perception study, the identification tests of two tone-pairs in Mandarin (T1-T2 and T1-T4) were conducted, using two sets of synthetic speech stimuli varying only along F0 continua. All groups/conditions showed categorical effects in perception. The CI group in the unimodal condition showed little difference from normal, while in the bimodal condition the categorical effect became weaker in identifying the T1-T4 continuum, with the category boundary more biased to T4. This suggests that bimodal CI children may need more fine grain adjustments of hearing aids to take full advantage of the bimodal technology.

Reactive agents are generally believed to be incapable of coping with perceptual ambiguity (i.e., identical sensory states that require different responses). However, a recent finding suggests that reactive agents can cope with perceptual ambiguity in a simple model (Nolfi, 2002). This paper investigates to what extent reactive and nonreactive agents can cope with perceptual ambiguity, and which strategies are employed when doing so. A model of active categorical perception (called Acp) is introduced. In Acp, situated agents with different types of neurocontrollers are optimized to categorize objects by adaptively coordinating action and perception. Our experiments show that both nonreactive and reactive agents can cope with perceptual ambiguity. An analysis of the behavior reveals that nonreactive agents use their internal memory to cope with perceptual ambiguity, while reactive agents use the environment as an external memory to compensate for their lack of an internal memory. We ...

The use of high-rise terminals, or uptalk, continues to be a point of contention in the study of intonation. Researchers continually produce conflicting descriptions of it in an effort to define it, including conflicting explanations of its connotation or significance in conversation. These difficulties suggest that ToBI, the most frequently used system of annotation for intonation, cannot adequately describe the contour. The definitions of uptalk produced using ToBI do not allow it to be distinguished from other contours, namely question intonation. This study tries to define the contour, not by describing it as ToBI does, but by measuring the pitch excursions that speakers produce in these contours in relation to the overall pitch range of the phrase in which it was produced. The results of the study show that the excursions produced in uptalk fall in the mid range of rises, steeper than those of other declarative statements, but not as steep as those produced in question intonation. This provides a potential set of criteria which can be used to precisely distinguish uptalk contours. The ability to identify contours based on the height of the pitch excursion exhibited also points to the possibility of the use of categorical perception of intonation contours by native speakers of English.

Human observers are remarkably proficient at recognizing expressions of emotions and at readily grouping them into distinct categories. When morphing one facial expression into another, the linear changes in low-level features are insufficient to describe the changes in perception, which instead follow an s-shaped function. Important questions are, whether there are single diagnostic regions in the face that drive categorical perception for certain parings of emotion expressions, and how information in those regions interacts when presented together. We report results from two experiments with morphed fear-anger expressions, where (a) half of the face was masked or (b) composite faces made up of different expressions were presented. When isolated upper and lower halves of faces were shown, the eyes were found to be almost as diagnostic as the whole face, with the response function showing a steep category boundary. In contrast, the mouth allowed for a substantially lesser amount of accuracy and responses followed a much flatter psychometric function. When a composite face consisting of mismatched upper and lower halves was used and observers were instructed to exclusively judge either the expression of mouth or eyes, the to-be-ignored part always influenced perception of the target region. In line with experiment 1, the eye region exerted a much stronger influence on mouth judgements than vice versa. Again, categorical perception was significantly more pronounced for upper halves of faces. The present study shows that identification of fear and anger in morphed faces relies heavily on information from the upper half of the face, most likely the eye region. Categorical perception is possible when only the upper face half is present, but compromised when only the lower part is shown. Moreover, observers tend to integrate all available features of a face, even when trying to focus on only one part.

Results: Listeners' responses were faster and their mouse trajectories closer to the ultimate behavioral selection (marked visually on the screen) in serial vs. random order, suggesting increased perceptual attraction to category exemplars. Interestingly, order effects emerged earlier and persisted later in the trial time course when categorizing speech in noise. Discussion: These data describe interactions between perceptual warping in categorization and speech-in-noise perception: warping strengthens the behavioral attraction to relevant speech categories, making listeners more decisive (though not necessarily more accurate) in their decisions of both clean and noise-degraded speech.

Speech perception requires the grouping of acoustic information into meaningful phonetic units via the process of categorical perception (CP). Environmental masking influences speech perception and CP. However, it remains unclear at which stage of processing (encoding, decision, or both) masking affects listeners' categorization of speech signals. The purpose of this study was to determine whether linguistic interference influences the early acousticphonetic conversion process inherent to CP. To this end, we measured source level, event related brain potentials (ERPs) from auditory cortex (AC) and inferior frontal gyrus (IFG) as listeners rapidly categorized speech sounds along a /da/ to /ga/ continuum presented in three listening conditions: quiet, and in the presence of forward (informational masker) and timereversed (energetic masker) 2-talker babble noise. Maskers were matched in overall SNR and spectral content and thus varied only in their degree of linguistic interference (i.e., informational masking). We hypothesized a differential effect of informational versus energetic masking on behavioral and neural categorization responses, where we predicted increased activation of frontal regions when disambiguating speech from noise, especially during lexical-informational maskers. We found (1) informational masking weakens behavioral speech phoneme identification above and beyond energetic masking; (2) low-level AC activity not only codes speech categories but is susceptible to higher-order lexical interference; (3) identifying speech amidst noise recruits a cross hemispheric circuit (ACleft → IFGright) whose engagement varies according to task difficulty. These findings provide corroborating evidence for top-down influences on the early acoustic-phonetic analysis of speech through a coordinated interplay between frontotemporal brain areas.

Surrounding context influences speech listening, resulting in dynamic shifts to category percepts. To examine its neural basis, event-related potentials (ERPs) were recorded during vowel identification with continua presented in random, forward, and backward orders to induce perceptual nonlinearities. Behaviorally, sequential order shifted listeners' categorical boundary vs. random delivery revealing perceptual warping (biasing) of the heard phonetic category dependent on recent stimulus history. ERPs revealed later (~300 ms) activity localized to superior temporal and middle/inferior frontal gyri that predicted listeners' hysteresis magnitudes. Findings demonstrate that top-down, stimulus history effects on speech categorization are governed by interactions between frontotemporal brain regions.

Auditory Gestalt perception by grouping of species-specific vocalizations to a perceptual stream with a defined meaning is typical for human speech perception but has not been studied in non-human mammals so far. Here we use synthesized models of vocalizations (series of wriggling calls) of mouse pups (Mus domesticus) and show that their mothers perceive the call series as a meaningful Gestalt for the release of instinctive maternal behavior, if the inter-call intervals have durations of 100-400 ms. Shorter or longer inter-call intervals significantly reduce the maternal responsiveness. We also show that series of natural wriggling calls have inter-call intervals mainly in the range of 100-400 ms. Thus, series of natural wriggling calls of pups match the time-domain auditory filters of their mothers in order to be optimally perceived and recognized. A similar time window exists for the production of human speech and the perception of series of sounds by humans. Neural mechanisms for setting the boundaries of the time window are discussed.