Puzzle-solving science: the quixotic quest for units in speech perception

Although speech signals are continuous and variable, listeners experience segmentation and linguistic structure in perception. For years, researchers have tried to identify the basic building-block of speech perception. In that time, experimental methods have evolved, constraints on stimulus materials have evolved, sources of variance have been identified, and computational models have been advanced. As a result, the slate of candidate units has increased, each with its own empirical support. In this article, we endorse Grossberg's adaptive resonance theory (ART), proposing that speech units are emergent properties of perceptual dynamics. By this view, units only "exist" when disparate features achieve resonance, a level of perceptual coherence that allows conscious encoding. We outline basic principles of ART, then summarize five experiments. Three experiments assessed the power of social influence to affect phoneme-syllable competitions. Two other experiments assessed repetition effects in monitoring data. Together the data suggest that "primary" speech units are strongly and symmetrically affected by bottom-up and top-down knowledge sources.

Visual comparisons within and between object parts: evidence for a single-part superiority effect

Subjects judged whether two marks placed at different positions along a curved contour were physically the same. When targets were separated by a concave curvature extremum--corresponding to a part-boundary--decision latencies were longer than when they straddled an equally curved convex extremum, demonstrating a "single-part superiority effect". This difference increased with both stimulus duration and the magnitude of contour curvature. However, it disappeared when the global configuration was not consistent with a part-boundary interpretation, suggesting a critical role of global organization in part decomposition.

Abstract-concept learning and list-memory processing by capuchin and rhesus monkeys

Three capuchin monkeys (Cebus apella) touched the lower of 2 pictures (same) or a white rectangle (different), increased same/different abstract-concept learning (52% to 87%) with set-size increases (8 to 128 pictures), and were better than 3 rhesus monkeys (Macaca mulatta). Three other rhesus that touched the top picture before choices learned similar to capuchins but were better at list-memory learning. Both species' serial position functions were similar in shape and changes with retention delays. Other species showed qualitatively similar shape changes but quantitatively different time-course changes. In abstract-concept learning, qualitative similarity was shown by complete concept learning, whereas a quantitative difference would have been a set-size slope difference. Qualitative similarity is discussed in relation to general-process versus modular cognitive accounts.

Meaning through syntax: language comprehension and the reduced relative clause construction

A new explanation is proposed for a long standing question in psycholinguistics: Why are some reduced relative clauses so difficult to comprehend? It is proposed that the meanings of some verbs like race are incompatible with the meaning of the reduced relative clause and that this incompatibility makes sentences like The horse raced past the barn fell unacceptable. In support of their hypotheses, the authors show that reduced relatives of The horse raced past the barn fell type occur in naturally produced sentences with a near-zero probability, whereas reduced relatives with other verbs occur with a probability of about 1 in 20. The authors also support the hypotheses with a number of psycholinguistic experiments and corpus studies.

Conditional reasoning and conditionalization

In solving conditional reasoning problems, reasoners are assumed to compute the probability of the conclusion, conditionalizing first on the categorical premise, giving the knowledge-based component, and conditionalizing then on the conditional-statement premise, from which the assumption-based component is derived. Because reasoners find it difficult to compute the second-step conditionalization except when the conditional-statement premise is found to be related to the result of the first-step conditionalization as for modus ponens or, possibly, for modus tollens, the knowledge-based component generally dominates reasoning performance. After representing all the possible cases in which conditional-argument forms may appear, this approach was found to be consistent with the results from the 3 experiments reported in this study, whereas 2 alternative hypotheses account for only some of the results.

Cognition in the hearing impaired and deaf as a bridge between signal and dialogue: a framework and a model

This paper focuses on the role of cognition in visual language processing in the deaf and hard of hearing. Although there are modality-specific cognitive findings in the literature on comparisons across speech communication modes and language (sign and speech), there is an impressive bulk of evidence that supports the notion of general modality-free cognitive functions in speech and sign processing. A working-memory framework is proposed for the cognitive involvement in language understanding (sign and speech). On the basis of multiple sources of behavioural and neuroscience data, four important parameters for language understanding are described in some detail: quality and precision of phonology, long-term memory access speed, degree of explicit processing, and general processing and storage capacity. Their interaction forms an important parameter space, and general predictions and applications can be derived for both spoken and signed language conditions. The model is mathematically formulated at a general level, hypothetical ease-of-language-understanding (ELU) functions are presented, and similarities and differences from current working-memory and speech perception formulations are pointed out.

Constraints on definite article alternation in speech production: to "thee" or not to "thee"?

A recent study showed that the pronunciation of the definite article in English (as either a reduced "thuh" or an unreduced "thee") depends on a number of different factors, including the pronunciation, spelling, and stress assignment of the following word (Raymond, Fisher, & Healy, 2002). However, it is not clear from previous research whether these factors influenced performance implicitly in normal speech production or whether explicit knowledge of the object of the experiment was relied on. In Experiment 1, we examined implicit performance on pronunciation of the definite article and found more systematic behavior than had previously been observed but, again, an influence of the pronunciation, spelling, and stress assignment of the following word. In Experiment 2, we tested the influence of the following word on definite article production during language development for two groups of children 8 and 10 years of age. This experiment showed increasing use of the unreduced form during development and a further influence of orthography. We interpret these results in terms of an interaction between perception and production in which the production system makes use of generalizations on the basis of both phonological and orthographic representations generated in perception.

A dual-process model of belief and evidence interactions in causal reasoning

In three experiments, we examined how reasoners' preexisting beliefs about causal relations constrained their evaluation of covariation-based empirical evidence. Reasoners were presented with causal candidates that were a priori rated to be either believable or unbelievable, as well as information regarding the degree to which the cause and the effect covaried. Several findings supported the conclusion that preexisting beliefs about causal relations reflect knowledge of both causal mechanisms and covariation relations, that these sources of knowledge are represented independently and contribute independently to causal judgments, and that the evaluation of new empirical evidence is influenced differently by mechanism-based and covariation-based beliefs. Finally, we observed that reasoners were relatively accurate in evaluating the degree to which their judgments were sensitive to empirical evidence but were less able to judge how much their judgments were influenced by their prior beliefs. We present a dual-process model that provides a descriptive account of the boundary conditions for belief and evidence interactions in causal reasoning.

Driven by information: a tectonic theory of Stroop effects

The goal of avoiding distraction (e.g., ignoring words when naming their print colors in a Stroop task) is opposed intrinsically by the penchant to process conspicuous and correlated characteristics of the environment (e.g., noticing trial-to-trial associations between the colors and the words). To reconcile these opposing forces, the authors propose a tectonic theory of selective attention in which 2 memory-based structures--dimensional imbalance and dimensional uncertainty--drive selection by processing salient, surprising, and/or correlated information contained within and across stimulus dimensions. Each structure modulates the buildup of excitation to targets and the buildup of inhibition to distractors and to memories of previous stimuli. Tectonic theory is implemented to simulate the impact of 4 types of context on the presence, magnitude, and direction of congruity effects and task effects in the Stroop paradigm. The tectonic model is shown to surpass other formal models in explaining the range and diversity of Sroop effects.

The developmental origins of musicality

The study of musical abilities and activities in infancy has the potential to shed light on musical biases or dispositions that are rooted in nature rather than nurture. The available evidence indicates that infants are sensitive to a number of sound features that are fundamental to music across cultures. Their discrimination of pitch and timing differences and their perception of equivalence classes are similar, in many respects, to those of listeners who have had many years of exposure to music. Whether these perceptual skills are unique to human listeners is not known. What is unique is the intense human interest in music, which is evident from the early days of life. Also unique is the importance of music in social contexts. Current ideas about musical timing and interpersonal synchrony are considered here, along with proposals for future research.

Risikokommunikation bei Brustkrebsfrüherkennung und Hormonersatztherapie

Zusammenfassung. Kommunikation von Risiken beinhaltet oft eine Vermittlung von Statistiken. Ein Überblick über eine Reihe von Studien mit Laien und Experten ergibt, dass die Form, wie mathematisch äquivalente Risikoinformation kommuniziert wird, das Verständnis maßgeblich beeinflusst. Wurden die Prävalenz einer Krankheit (z.B. Brustkrebs) und die Güte eines medizinischen Tests (z.B. Mammographie) in Form von Wahrscheinlichkeiten kommuniziert, konnten nur ca. 15% der Probanden die Bedeutung eines positiven Testbefunds richtig einschätzen. Bei Verwendung natürlicher Häufigkeiten, wie sie sich durch die Auszählung von beobachteten Einzelfällen in einer natürlichen Umgebung ergeben, waren es 50%. Ebenso ergeben frühere Studien zur Teilnahmebereitschaft an Screeningprogrammen, dass die Kommunikation des Nutzens eines solchen Programms in Form der absoluten versus relativen Risikoreduktion einen Effekt hat. Die hier berichtete Studie zur Brustkrebsfrüherkennung konnte diesen allerdings nicht replizieren. Abschließend werden Risiken und Nutzen der Hormonersatztherapie vorgestellt sowie Ergebnisse einer Umfrage berichtet, die Defizite beim Verständnis der relativen und absoluten Risikoreduktion in diesem Kontext aufgezeigt hat.

Naive Biologie im kindlichen Denken:

Zusammenfassung. In der kognitiven Entwicklungspsychologie wird bereits seit einigen Jahren die Entwicklung bereichsspezifischen Wissens innerhalb fundamentaler Rahmentheorien, v.a. in den Wissensbereichen naive Physik, Biologie und Psychologie untersucht. Von besonderer Bedeutung ist dabei die Frage, ob Kinder kausale Mechanismen verschiedener Domänen (z.B. intentionale vs. mechanische Verursachung) auseinanderhalten können. In der vorliegenden Arbeit ging es um die Differenzierung zwischen naiver Biologie und Soziologie. Gelingt diese Differenzierung, sollten Kinder zwischen Beziehungen, die biologisch bedingt sind (Verwandtschaftsbeziehungen) und solchen, die sozial bedingt sind (Freundschafts- oder Nachbarschaftsbeziehungen), unterscheiden können. Je 25 vier- und sechsjährige Kindergartenkinder wurden in zwei Teilstudien mit kleinen Aufgaben konfrontiert, bei denen sie zwischen Personen ihres erfahrbaren Umfeldes (Eltern, Geschwister, Großeltern, Freunde, Kindergärtnerin, Kinderarzt) anhand des Beziehungstyps differenzieren sollten. Wissen Vorschulkinder, dass Verwandtschaftsbeziehungen auf bestimmte Personen begrenzt sind, Bekanntschaftsbeziehungen hingegen nicht (Teilstudie 1)? Unterscheiden sie zwischen Geschwistern und Freunden bezüglich eines möglichen Anfangs und Endes einer Beziehung (Teilstudie 2)? Für die hier gewählten Indikatoren zeigten sich deutliche Entwicklungsfortschritte im Altersbereich zwischen vier und sechs Jahren. Während die jüngeren Kinder noch keine deutliche Differenzierungsleistung zwischen Verwandtschafts- und Bekanntschaftsbeziehungen zeigen, scheinen die älteren sechsjährigen Kinder für die Besonderheit von Familienbeziehungen sensibilisiert zu sein. Die Ergebnisse weisen darauf hin, dass erst gegen Ende des Vorschulalters ein Verständnis spezifisch biologischer Kausalität im Sinne einer domänspezifischen Theorie erworben wird.

Children's performance on a false-belief task is impaired by activation of an evolutionarily-canalized response system

We examine whether children's performance on a false-belief task is impaired by task content that activates an early-developing, prepotent motivational system: predator-avoidance. In two studies (N = 46 and N = 37), children aged 3-4 years completed variants of a false-belief task that involved predator-avoidance, playmate-avoidance, prey-seeking, and playmate-seeking, respectively. The proportion of correct answers on the playmate-avoidance task (Study 1: 52%; Study 2: 51%) was significantly greater than the proportion of correct answers on the analogous predator-avoidance task (Study 1: 28%; Study 2: 22%). This difference was not an artifact of children generally performing better on playmate stories than on predator-prey stories. The findings are consistent with the hypothesis that activation of the predator-avoidance system generates prepotent response patterns that pre-empt full consideration of the mental states of the prey characters in false-belief stories.

Lexical access and phonological decoding in adult dyslexic subtypes

Lexical access and phonological decoding were tested in 100 normal adult readers and 21 adult dyslexic individuals. Within the dyslexic sample, 11 dysphonetic dyslexic and 10 dyseidetic dyslexic participants were classified on the basis of spelling patterns. In the 1st experiment, adult dyseidetic readers showed a marked deficit on the lexical-access decision task in comparison with adult dysphonetic readers. In the 2nd experiment, the phonological-decoding decision task did not separate the subtypes. A lexical-access deficit in adult dyseidetic dyslexia cannot be explained in terms of a developmental delay. A phonological-decoding deficit in adult dyseidetic dyslexia may be explained by increased involvement of the lexical procedure in phonological assembly under an analogy strategy.

Representation of lexical form

The authors attempted to determine whether surface representations of spoken words are mapped onto underlying, abstract representations. In particular, they tested the hypothesis that flaps--neutralized allophones of intervocalic /t/s and /d/s--are mapped onto their underlying phonemic counterparts. In 6 repetition priming experiments, participants responded to stimuli in 2 blocks of trials. Stimuli in the 1st block served as primes and those in the 2nd as targets. Primes and targets consisted of English words containing intervocalic /t/s and /d/s that, when produced casually, were flapped. In all 6 experiments, reaction times to target items were measured as a function of prime type. The results provide evidence for both surface and underlying form-based representations.

The development of teleological versus mentalizing observational learning strategies in infancy

The author introduces the concept of mentalization as a central interpretative mechanism of social reality testing. It is argued that developmentally the emergence of this mentalizing capacity to interpret other people's actions in terms of their causal intentional mind states (such as beliefs, desires, intentions, and emotions) is preceded by an earlier, nonmentalistic, teleological action interpretational system that represents others' actions in terms of their concrete and visible outcomes. Then the early psychosocial determinants of the developmental unfolding of our mentalizing capacity are considered from the points of view of attachment theory and developmental psychopathology. It is argued that, in severely dysfunctional (neglecting, abusive, and/or dissociative) caregiving environments, the development of mentalization becomes inhibited and results in a predominantly teleological, nonmentalistic interpretation of intimate attachment relationships that is a core feature of certain developmental psychopathologies such as borderline personality disorder. The normal developmental shift from a teleological to a mentalistic mode of action interpretation is illustrated in terms of recently discovered qualitative changes in imitative and observational learning styles during infancy. It is hypothesized that these changes are related to the infant's developing capacity to interpret the communicative-referential behavioral cues that frame the caregiver's infant-directed actions as signaling a cooperative and benevolent mentalistic attitude toward the baby. In closing, it is proposed that the hypothesized role of severely dysfunctional attachment environments in inhibiting the establishment of mentalization skills could be directly tested in early development in the domain of observational learning. It is predicted that differential patterns of "teleological emulation" versus "mentalistic imitative learning" will be found in infants raised in severely dysfunctional versus congenial and secure caregiving contexts, respectively.

What makes viewpoint-invariant properties perceptually salient?

It has been noted that many of the perceptually salient image properties identified by the Gestalt psychologists, such as collinearity, parallelism, and good continuation, age invariant to changes in viewpoint. However, I show that viewpoint invariance is not sufficient to distinguish these Gestalt properties; one can define an infinite number of viewpoint-invariant properties that are not perceptually salient. I then show that generally, the perceptually salient viewpoint-invariant properties are minimal, in the sense that they can be derived by using less image information than for nonsalient properties. This finding provides support for the hypothesis that the biological relevance of an image property is determined both by the extent to which it provides information about the world and by the ease with which this property can be computed. [An abbreviated version of this work, including technical details that are avoided in this paper, is contained in K. Boyer and S. Sarker, eds., Perceptual Organization for Artificial Vision Systems (Kluwer Academic, Dordrecht, The Netherlands, 2000), pp. 121-138.]

Inhibitory priming effects in auditory word recognition: when the target's competitors conflict with the prime word

Several studies indicate that the number of similar sounding words that are activated during recognition is a powerful predictor of performance on auditory targets. Words with few competitors are processed more quickly and accurately than words with many competitors. In the present study, we examined the contribution of the competitor set size in determining the magnitude of the inhibitory priming effect. The data show that the priming effect is stronger when word targets have few competitors. This result supports the view of direct competition between lexical candidates.

Acute effects of alcohol on hemodynamic changes during visual stimulation assessed using 24-channel near-infrared spectroscopy

The purpose of this study was to evaluate the effects of alcohol on hemodynamic changes induced by visual stimulation. Ten healthy human subjects were examined using Optical Topography((R)) (Hitachi Medical Corporation: ETG-100). Each subject gradually drank 0.4 ml/kg alcohol over 10 min. Changes in oxy-hemoglobin (Hb), deoxy-Hb and total-Hb concentration were measured five times: 20 min before alcohol intake, immediately after alcohol intake, and at 20, 40 and 60 min after alcohol intake. A questionnaire was used to assess subjective feelings of alcohol. Blood-alcohol concentration (BAC) was estimated from ethanol concentration in expired air four times: immediately after alcohol intake and at 20, 40 and 60 min after alcohol intake. The visual stimulation tool was a checkerboard. It showed alternations of black and red patterns at a frequency of 8 Hz. The stimulus was displayed for 10 s after a rest of 30 s. The stimulus was repeated 10 times. Oxy-Hb concentration increased and deoxy-Hb concentration decreased during visual stimulation before and after alcohol intake, despite changes in the score of subjective feelings of alcohol and BAC. Alcohol intake does not significantly affect hemodynamic changes caused by visual stimulation in the visual cortex.

Visual lateralization in the bottlenose dolphin (Tursiops truncatus): evidence for a population asymmetry?

A previous behavioural study with a single bottlenose dolphin had reported a right eye superiority in visual discrimination tasks, indicating a left hemisphere dominance for visual object processing. The presence of a functional asymmetry demonstrated with one individual shows that this function can be lateralized in this single animal, but cannot reveal if this represents a population asymmetry. Therefore, we conducted a series of visual discrimination experiments with three individuals of Tursiops truncatus under monocular conditions. The tested animals had to distinguish between simultaneously presented stimulus pairs of different patterns, whereby one stimulus was always defined to be correct. Additionally, the animals were observed for their free eye use during training and introduction of new items. The present data set revealed a right eye advantage (left hemisphere dominance) for all tested animals and a predominance of right eye use during daily activities. These results make it possible that bottlenose dolphins are lateralized for visual pattern discrimination at the level of a population asymmetry. Against the background of similar data in other vertebrates, a left hemisphere dominance for pattern discrimination points to the possibility that dolphins exploit local visual details instead of global configurational features to recognize and memorize visual stimuli.

The mechanism of self-recognition in humans

Recognizing oneself as the owner of a body and the agent of actions requires specific mechanisms which have been elucidated only recently. One of these mechanisms is the monitoring of signals arising from bodily movements, i.e. the central signals which contribute to the generation of the movements and the sensory signals which arise from their execution. The congruence between these two sets of signals is a strong index for determining the experiences of ownership and agency, which are the main constituents of the experience of being an independent self. This mechanism, however, does not account from the frequent cases where an intention is generated but the corresponding action is not executed. In this paper, it is postulated that such covert actions are internally simulated by activating specific cortical networks or representations of the intended actions. This process of action simulation is also extended to the observation and the recognition of actions performed or intended by other agents. The problem of disentangling representations that pertain to self-intended actions from those that pertain to actions executed or intended by others, is a critical one for attributing actions to their respective agents. Failure to recognize one's own actions and misattribution of actions may result from pathological conditions which alter the readability of these representations.

The remarkable inefficiency of word recognition

Do we recognize common objects by parts, or as wholes? Holistic recognition would be efficient, yet people detect a grating of light and dark stripes by parts. Thus efficiency falls as the number of stripes increases, in inverse proportion, as explained by probability summation among independent feature detectors. It is inefficient to detect correlated components independently. But gratings are uncommon artificial stimuli that may fail to tap the full power of visual object recognition. Familiar objects become special as people become expert at judging them, possibly because the processing becomes more holistic. Letters and words were designed to be easily recognized, and, through a lifetime of reading, our visual system presumably has adapted to do this as well as it possibly can. Here we show that in identifying familiar English words, even the five most common three-letter words, observers have the handicap predicted by recognition by parts: a word is unreadable unless its letters are separately identifiable. Efficiency is inversely proportional to word length, independent of how many possible words (5, 26 or thousands) the test word is drawn from. Human performance never exceeds that attainable by strictly letter- or feature-based models. Thus, everything seen is a pattern of features. Despite our virtuosity at recognizing patterns and our expertise from reading a billion letters, we never learn to see a word as a feature; our efficiency is limited by the bottleneck of having to rigorously and independently detect simple features.

Nonconscious formation and reactivation of semantic associations by way of the medial temporal lobe

A successful strategy to memorize unrelated items is to associate them semantically. This learning method is typical for declarative memory and depends on the medial temporal lobe (MTL). Yet, only a small fraction of perceived items emerge into conscious awareness and receive the status of representations in declarative memory. This functional magnetic resonance imaging (fMRI) study tackled the mnemonic fate of unrelated item pairs processed without conscious awareness. Stimuli consisted of a face and a written profession (experimental condition) or of a face (control condition) exposed very briefly between pattern masks. Although the participants were unaware of the stimuli, activity in the hippocampus and perirhinal cortex was changed in the experimental versus the control condition; perirhinal activity changes correlated with the reaction time measure of the later nonconscious retrieval. For retrieval, the previously presented faces were shown again, this time for conscious inspection. The task was to guess the professional category of each face. This task was to induce a nonconscious retrieval of previously formed face-profession associations. Remarkably, activity in the hippocampus and perirhinal cortex was enhanced when subjects were confronted with faces from the experimental versus the control condition. The degree of hippocampal and perirhinal activation changes correlated with the reaction time measure of nonconscious retrieval. Together, our findings suggest that new semantic associations can be formed and retrieved by way of the medial temporal lobe without awareness of the associations or its components at encoding or any awareness that one is remembering at retrieval.

Seeing and hearing speech excites the motor system involved in speech production

The perception of action is associated with increased activity in motor regions, implicating such regions in the recognition, understanding and imitation of actions. We examined the possibility that perception of speech, both auditory and visual, would also result in changes in the excitability of the motor system underlying speech production. Transcranial magnetic stimulation was applied to the face area of primary motor cortex to elicit motor-evoked potentials in the lip muscles. The size of the motor-evoked potentials was compared under the following conditions: listening to speech, listening to non-verbal sounds, viewing speech-related lip movements, and viewing eye and brow movements. Compared to control conditions, listening to and viewing speech enhanced the size of the motor-evoked potential. This effect was only seen in response to stimulation of the left hemisphere; stimulation of the right hemisphere produced no changes in motor-evoked potentials in any of the conditions. In a control experiment, the size of the motor-evoked potentials elicited in the muscles of the right hand did not differ among conditions, suggesting that speech-related changes in excitability are specific to the lip muscles. These results provide evidence that both auditory and visual speech perception facilitate the excitability of the motor system involved in speech production.

Reference frames for orientation anisotropies in face recognition and biological-motion perception

Both face recognition and biological-motion perception are strongly orientation-dependent. Recognition performance decreases if the stimuli are rotated with respect to their normal upright orientation. Here, the question whether this effect operates in egocentric coordinates or in environmental coordinates is examined. In addition to the use of rotated stimuli the observers were also rotated and tested both with a same-different face-recognition task and with a biological-motion detection task. A strong orientation effect was found that depended only on the stimulus orientation relative to the observer. This result clearly indicates that orientation effects in both stimulus domains operate in an egocentric frame of reference. This finding is discussed in terms of the particular requirement of extracting sophisticated information for social recognition and communication from faces and biological motion.

AAC performance and usability issues: the effect of AAC technology on the communicative process

In this article, Clark's theory of language use is applied to the study of conversations of augmented speakers and their addressees. Discussion focuses on how shared meaning--called common ground--is achieved, the process of grounding utterances under real-time constraints, and how the media characteristics of devices affect the grounding process. A joint action analysis of grounding will be applied to examples of word-board and Voice Output Communication Aid (VOCA)-mediated conversations to show how participants organize their talk around specific media constraints to conduct their conversations and solve communication problems. The authors argue that this model of device-mediated communication performance, or some variety of it, has the potential to reconcile many of the individual research findings in this field within a single explanatory framework. If successful, this approach could be used to evaluate future research with an empirically-based model of communication performance.

Interpreting gaze in Turner syndrome: impaired sensitivity to intention and emotion, but preservation of social cueing

Women with Turner's syndrome (TS), who lack a complete X-chromosome, show an impairment in remembering faces and in classifying "fear" in face images. Could their difficulties extend to the processing of gaze? Three tasks, all of which rely on the ability to make use of the eye-region of a pictured face, are reported. Women with TS were impaired at judging mental state from images of the upper face ("reading the mind in the eyes"). They were also specifically impaired at interpreting "fear" from displays of the eye-region of the face. However, they showed normal susceptibility to direction of gaze as an attentional cue (social cueing), since they were as sensitive as controls to the validity of the cue, under conditions where it should be ignored. In this task, unlike those of reading the upper face for intention or expression, PIQ accounted for a significant amount of individual variance in task performance. The processing of displays of the eye region affording social and affective information is specifically affected in TS. We speculate that amygdala dysfunction is likely to be implicated in this anomalous behaviour. The presence in the female karyotype of two complete X-chromosomes is protective for some socio-cognitive abilities related to the modulation of behaviour by the interpretation of gaze.

A chimeric point-light walker

Ambiguity has long been used as a probe into visual processing. Here, we describe a new dynamic ambiguous figure-the chimeric point-light walker--which we hope will prove to be a useful tool for exploring biological motion. We begin by describing the construction of the stimulus and discussing the compelling finding that, when presented in a mask, observers consistently fail to notice anything odd about the walker, reporting instead that they are watching an unambiguous figure moving either to the left or right. Some observers report that the initial percept fluctuates, moving first to the left, then to the right, or vice versa; others always perceive a constant direction. All observers, when briefly shown the unmasked ambiguous figure, have no difficulty in perceiving the novel motion pattern once the mask is returned. These two findings--the initial report of unambiguous motion and the subsequent 'primed' perception of the ambiguity--are both consistent with an important role for top-down processing in biological motion. We conclude by suggesting several domains within the realm of biological-motion processing where this simple stimulus may prove to be useful.

Spatial representation and attention in toddlers with Williams syndrome and Down syndrome

The nature of the spatial representations that underlie simple visually guided actions early in life was investigated in toddlers with Williams syndrome (WS), Down syndrome (DS), and healthy chronological age- and mental age-matched controls, through the use of a "double-step" saccade paradigm. The experiment tested the hypothesis that, compared to typically developing infants and toddlers, and toddlers with DS, those with WS display a deficit in using spatial representations to guide actions. Levels of sustained attention were also measured within these groups, to establish whether differences in levels of engagement influenced performance on the double-step saccade task. The results showed that toddlers with WS were unable to combine extra-retinal information with retinal information to the same extent as the other groups, and displayed evidence of other deficits in saccade planning, suggesting a greater reliance on sub-cortical mechanisms than the other populations. Results also indicated that their exploration of the visual environment is less developed. The sustained attention task revealed shorter and fewer periods of sustained attention in toddlers with DS, but not those with WS, suggesting that WS performance on the double-step saccade task is not explained by poorer engagement. The findings are also discussed in relation to a possible attention disengagement deficit in WS toddlers. Our study highlights the importance of studying genetic disorders early in development.

Attentional capture within and between objects

The present study addressed the question whether attentional capture by abrupt onsets is affected by object-like properties of the stimulus field. Observers searched for a target circle at one of four ends of two solid rectangles. In the focused attention condition the location of the upcoming target was cued by means of a central arrowhead, whereas in the divided attention condition, the target location was not cued. Irrelevant abrupt onsets could appear either within the attended or within the non-attended object. The results showed that in the focused attention condition, onsets ceased to capture attention irrespective of whether the onset appeared within an attended object or within a non-attended object.

Predicting events of varying probability: uncertainty investigated by fMRI

Many everyday life predictions rely on the experience and memory of event frequencies, i.e., natural samplings. We used functional magnetic resonance imaging (fMRI) to investigate the neural substrates of prediction under varying uncertainty based on a natural sampling approach. The study focused particularly on a comparison with other types of externally attributed uncertainty, such as guessing, and on the frontomedian cortex, which is known to be engaged in many types of decisions under uncertainty. On the basis of preceding stimulus cues, participants predicted events that occurred with probabilities ranging from p = 0.6 to p = 1.0. In contrast to certain predictions in a control task, predictions under uncertainty elicited activations within a posterior frontomedian area (mesial BA 8) and within a set of subcortical areas which are known to subserve dopaminergic modulations. The parametric analysis revealed that activation within the mesial BA 8 significantly increased with increasing uncertainty. A comparison with other types of uncertainty indicates that frontomedian correlates of frequency-based prediction appear to be comparable with those induced in long-term stimulus-response adaptation processes such as hypothesis testing, in contrast to those engaged in short-term error processing such as guessing.

Sensory perception during sleep and meditation: common features and differences

Sleep and meditation are both physiological conditions in which peripheral sensory input is voluntarily reduced, but sensory perception of internally generated information continues. However, the two conditions differ in the level of awareness retained.

Age differences in working memory--the roles of storage and selective access

Twenty-four young (23 years) and 24 old (71 years) adults performed arithmetic tasks with working memory loads ranging from 1 to 4. Age groups were equivalent in mean accuracy and speed of arithmetic operations under minimal working memory load, but old adults were slower than young with memory demands >1. Access to a new object in working memory as the basis of computation required additional time. This object-switching cost increased with increases in memory demand, but was unaffected by age, indicating that old adults have no deficit in selective access to working memory.

Inference suppression and semantic memory retrieval: every counterexample counts

Reasoning with conditionals involving causal content is known to be affected by retrieval of counterexamples from semantic memory. In this study we examined the characteristics of this search process in everyday conditional reasoning. In Experiment 1 we manipulated the number (zero to four) of explicitly presented counterexamples (alternative causes or disabling conditions) for causal conditionals. In Experiment 2, using a generation pretest, we measured the number of counterexamples participants could retrieve for a set of causal conditionals. One month after the pretest, participants were presented a reasoning task with the same conditionals. The experiments indicated that acceptance of modus ponens linearly decreased with every additionally retrieved disabler, whereas affirmation of the consequent acceptance linearly decreased as a function of the number of retrieved alternatives. Results for denial of the antecedent and modus tollens were less clear. The findings show that the search process does not necessarily stop after retrieval of a single counterexample and that every additional counterexample has an impact on the inference acceptance.

Signing enhances memory like performing actions

In three experiments, we investigated the influence of the overt performance of signs on memory. Deaf and hearing participants studied lists of action phrases (Experiment 1) or nouns (Experiment 2) under standard verbal instruction, under the instructions to sign the verbal phrase, to symbolically perform the denoted action, or to carry out a prototypical action corresponding to each noun. Higher recall and recognition performances were observed when actions were performed than in the verbal encoding condition, and signing was as effective for memory as was enactment. Thus, overt signing can induce an enactment effect. In contrast, Experiment 3 demonstrated that performing an unrelated action did not. A unique but unrelated action was not memory efficient.

Paralinguistic correlates of conceptual structure

How is conceptual knowledge transmitted during conversation? When a speaker refers to an object, the name that the speaker chooses conveys information about category identity. In addition, I propose that a speaker's confidence in a classification can convey information about category structure. Because atypical instances of a category are more difficult to classify than typical instances, when speakers refer to these instances their lack of confidence will manifest itself "paralinguistically"--that is, in the form of hesitations, filled pauses, or rising prosody. These features can help listeners learn by enabling them to differentiate good from bad examples of a category. So that this hypothesis could be evaluated, in a category learning experiment participants learned a set of novel colors from a speaker. When the speaker's paralinguistically expressed confidence was consistent with the underlying category structure, learners acquired the categories more rapidly and showed better category differentiation from the earliest moments of learning. These findings have important implications for theories of conversational coordination and language learning.

Perceiving numbers causes spatial shifts of attention

Number symbols are part of our everyday visual world. Here we show that merely looking at numbers causes a shift in covert attention to the left or right side, depending upon the number's magnitude. This observation implies obligatory activation of number meaning and signals a tight coupling of internal and external representations of space.

The difference engine: a model of diversity in speeded cognition

A theory of diversity in speeded cognition, the difference engine, is proposed, in which information processing is represented as a series of generic computational steps. Some individuals tend to perform all of these computations relatively quickly and other individuals tend to perform them all relatively slowly, reflecting the existence of a general cognitive speed factor, but the time required for response selection and execution is assumed to be independent of cognitive speed. The difference engine correctly predicts the positively accelerated form of the relation between diversity of performance, as measured by the standard deviation for the group, and task difficulty, as indexed by the mean response time (RT) for the group. In addition, the difference engine correctly predicts approximately linear relations between the RTs of any individual and average performance for the group, with the regression lines for fast individuals having slopes less than 1.0 (and positive intercepts) and the regression lines for slow individuals having slopes greater than 1.0 (and negative intercepts). Similar predictions are made for comparisons of slow, average, and fast subgroups, regardless of whether those subgroups are formed on the basis of differences in ability, age, or health status. These predictions are consistent with evidence from studies of healthy young and older adults as well as from studies of depressed and age-matched control groups.

Conceptual Change: kognitiv oder situiert?

Zusammenfassung: Es werden zwei kognitive Ansätze zu Conceptual Change ausführlich dargestellt: der “Rahmentheorieansatz” von Vosniadou ( Vosniadou & Brewer, 1992 ) und der “Kategorisierungsansatz” von Chi (1992) . Vosniadou beschreibt Conceptual Change als graduelle Revision mentaler Modelle, bei Chi wird Conceptual Change als Überwindung von ontologischen Kategorisierungsfehlern konzipiert. Beide “Defizit orientierten” Ansätze werden aus einer situierten Perspektive kritisiert. Hierbei werden das Verdinglichungsproblem sowie Probleme des vernachlässigten Kontexts, der Wissensdiagnostik, der Fokussierung auf initiales Lernen in wohl strukturierten Domänen und schließlich das Problem des kognitiven Bias diskutiert. Als Beispiel für einen situierten Ansatz wird ein Kontextmodell von Caravita und Halldén (1994) vorgestellt. Zudem wird auf die “radikale” situierte Position von Säljö (1999) eingegangen. Im Ausblick werden Möglichkeiten einer gegenseitigen Befruchtung kognitiver und situierter Conceptual-Change-Ansätze diskutiert.

Configural information is processed differently in perception and recognition of faces

Several previous studies have stressed the importance of processing configural information in face recognition. In this study the perception of configural information was investigated. Large overestimations were found when the eye-mouth distance and the inter-eye distance had to be estimated. Whereas configural processing is disrupted when inverted faces have to be recognized the perceptual overestimations persisted when faces were inverted. These results suggest that processing configural information is different in perceptual as opposed to recognition tasks.

Weak coherence, no theory of mind, or executive dysfunction? Solving the puzzle of pragmatic language disorders

Deficits in pragmatic language ability are common to a number of clinical populations, for example, right-hemisphere damage (RHD), Autism and traumatic brain injury (TBI). In these individuals the basic structural components of language may be intact, but the ability to use language to engage socially is impaired. Despite the nature of these difficulties being well documented, exactly what causes these difficulties is less clear. Furthermore, the current status of causal explanations for pragmatic difficulties across these populations is divergent and sometimes contradictory. This paper explores the empirical validity of three theories that attempt to explain pragmatic language impairment. It is recommended that a new, more convergent approach to investigating the causes of pragmatic language disability be adopted.