Representation and competition in the perception of spoken words

We present data from four experiments using cross-modal priming to examine the effects of competitor environment on lexical activation during the time course of the perception of a spoken word. The research is conducted from the perspective of a distributed model of speech perception and lexical representation, which focuses on activation at the level of lexical content. In this model, the strength of competition between simultaneously active lexical items depends on the degree of coherence between their distributed semantic and phonological representations. Consistent with this model, interference effects are more complete when the purely semantic aspects of these coactive representations are probed (using semantic priming) than when phonological aspects are probed as well (using repetition priming).     

Gradient effects of within-category phonetic variation on lexical access

In order to determine whether small within-category differences in voice onset time (VOT) affect lexical access, eye movements were monitored as participants indicated which of four pictures was named by spoken stimuli that varied along a 0-40 ms VOT continuum. Within-category differences in VOT resulted in gradient increases in fixations to cross-boundary lexical competitors as VOT approached the category boundary. Thus, fine-grained acoustic/phonetic differences are preserved in patterns of lexical activation for competing lexical candidates and could be used to maximize the efficiency of on-line word recognition.     

Action alters shape categories

Two experiments show that action alters the shape categories formed by 2-year-olds. Experiment 1 shows that moving an object horizontally (or vertically) defines the horizontal (or vertical) axis as the main axis of elongation and systematically changes the range of shapes seen as similar. Experiment 2 shows that moving an object symmetrically (or asymmetrically) also alters shape categories. Previous work has shown marked developmental changes in object recognition between 1 and 3 years of age. These results suggest a role for action in this developmental process.     

Establishing visual category boundaries between objects: a PET study

Individuals with Alzheimer's disease (AD) often have problems in recognizing common objects. This visual agnosia may stem from difficulties in establishing appropriate visual boundaries between visually similar objects. In support of this hypothesis, showed that AD subjects have difficulties in establishing visual category boundaries between continuously graded shapes. In an attempt to investigate the neural basis of these impairments, the current study required a group of neurologically healthy elderly participants to categorically classify a series of ellipses varying in width while regional blood flow changes were measured using positron emission tomography (PET). Two categorization conditions were compared in order to isolate changes in cortical activity that dissociated the categorization of shapes situated either near or far from a category boundary that divided the width continuum. The participants produced a discontinuity in the probability and speed of categorizing the shapes at some point along the continuum, suggesting that the objects were classified into distinct categories. Moreover, a comparison of the PET scans obtained while the subjects were categorizing the shapes situated near vs. far form the category boundary revealed significant differences in cortical activity in the parietal and frontal brain areas. These findings suggest that both visuo-spatial and decision making mechanisms may be involved in establishing categorical distinctions between continuously graded stimuli. It is proposed that the functional role of the parietal and frontal cortical regions in establishing visual boundaries between categories of objects may be relevant for understanding object recognition impairments in AD.     

Classifying homicide offenders and predicting their characteristics from crime scene behavior

A theoretical distinction between instrumental and expressive aggression was used in analyzing offender characteristics and their associations with crime scene actions in Finnish homicides. Twenty-one variables reflecting the offenders' criminal activity, previous relationships with intimates and victims, and general social and psychological adjustment were derived from files of single-offender/single-victim homicides occurring between 1980 and 1994 (n = 502). Additionally, three variables describing post-offense actions and police interview behavior were included. A multidimensional scaling procedure was used to investigate the interrelationships between the variables. A distinction between expressive and instrumental characteristics was observable in the empirical structure, which was divided into three subthemes of Instrumental, Expressive: Blood, and Expressive: Intimate. Associations between the characteristics with five previously identified subthemes of crime scene actions were computed. In addition, the subthemes of crime scene actions were related to post-offense actions and police interview behavior, with Expressive themes being associated with less denial as well as a greater likelihood of surrendering and confession. The practical usefulness for police investigations and theoretical implications of the results are discussed.     

Event-related brain potential correlates of the other-race effect: A review

People are better at remembering own-race relative to other-race faces. Here, we review event-related brain potential (ERP) correlates of this so-called other-‘race’ effect (ORE) by discussing three critical aspects that characterize the neural signature of this phenomenon. First, difficulties with other-race faces initially emerge during perceptual processing, which is indexed by an increased N170. Second, as evidenced by ‘difference due to subsequent memory’ effects, more effortful processing of other-race faces is needed for successful encoding into long-term memory. Third, ERP old/new effects reveal that a stronger engagement of processing resources is also required for successful retrieval of other-race faces from memory. The ERP evidence available to date thus suggests widespread ethnicity-related modulations during both perceptual and mnemonic processing stages. We further discuss how findings from the ORE compared with potentially related memory biases (e.g. other-gender or other-age effects) and how ERP findings inform the ongoing debate regarding the mechanisms underlying the ORE. Finally, we outline open questions and potential future directions with an emphasis on using multiple, ecologically more valid ‘ambient’ images for each face to assess the ORE in paradigms that capture identity rather than image recognition.     

Differential ordering of objects and attributes

By reference to nominated attributes, a genus, being a population of objects of one specified kind, may be partitioned into species, being subpopulations of different kinds. A prototype is an object representative of its species within the genus. Using this framework, the paper describes how objects can be relatively differentiated with respect to attributes, and how attributes can be relatively differentiating with respect to objects. Methods and rationale for such differential ordering of objects and attributes are presented by example, formal development, and application.For a genus comprisingn species of object there is a subsetP ofn distinct prototypes. With respect tom nominated attributes, each object in has anm-element characterization. Together these determine ann ×m objects × attributes matrix, the rows of which are the characterizations of the prototypical objects. Over then species in , an associated relative frequency vector gives the distribution of objects (and of their characterizations). The matrix and vector associate the objects in with points in a metric space (P, ); and it is with respect to various sums of distances in this attribute space that one can differentially order objects and attributes.The definition of the distance function is generalized across kinds of difference, types of characterization, scale-types of measurement, Minkowskiindex 1, and any form of distribution of objects over species. Explanatory and taxonomic applications in psychology and other fields are discussed, with focus on classification, identification, recognition, and search. The Braille code and the identification of its characters provide illustration.An anticipation and some preliminary indications were given in Sutcliffe and Bristow (1966), Sutcliffe (1972, 1973), and Nowakowska (1975). Subsequently the ideas have been extended and their applications realized in a computer program which, in its development, has so far gone through many minor and three major revisions to its present form in Sutcliffe (1985). The foregoing provided the foundation for the empirical applications and for the presentation in this paper of the ideas in their general form. the research has been supported by funds from the University of Sydney Research Grant and from the Australian Research Grants Scheme. In the working out and exposition of the ideas I have very much benefited from constructive critical comment given by C. R. Latimer, J. B. Michell, G. Oliphant, and E. Seneta, and from the professional programming skills of Michael Wilson and David Shillito. I am grateful for the invitation and the facilities for writing extended during 1983 by Georges Noizet, Laboratoire de Psychologie Expérimentale, Université René Descartes, Paris V, and by Samuel Messick, Vice President for Research, E.T.S. Princeton, N.J. Finally, I acknowledge the improvements in presentation of this paper which have arisen from the editor's and reviewers' comments.     

The role of generation in recognition

In contrast to the widely accepted opinion, a negatively accelerated RT function was obtained with varied mapping of stimuli to responses in Sternberg's (1966) recognition task when the task was designed to reduce proactive inhibition. These results are similar to the results obtained in the distractor task. Those aspects of the distractor task that proactively inhibit recall of the trigram are also necessary to produce a linear RT function in the recognition task. Hence, the varied-set procedure only results in a linear RT function when the memory sets on successive trials contain similar items, but not when successive trials contain different kinds of items, e.g., digits versus letters. Also, once subjects have been trained on the fixed-set procedure to produce a negatively accelerated RT function, the training transfers completely and immediately to entirely new sets of targets and distractors. The results of both tasks, as well as other retrieval tasks, can be explained by a model containing a single comparison process and an optional serial generation process which is invoked to increase the discriminability of the memory set from distractors.     

Masking the face: Recognition of emotional facial expressions as a function of the parameters of backward masking

Four experiments are reported investigating recognition of emotional expressions in very briefly presented facial stimulus. The faces were backwardly masked by neutral facial displays and recognition of facial expressions was analyzed as a function of the manipulation of different parameters in the masking procedure. The main conclusion was that stimulus onset asynchrony between target and mask proved to be the principal factor influencing recognition of the masked expressions. In general, confident recognitions of facial expressions required about 100–150 msec, with shorter time for happy than for angry expressions. The manipulation of the duration of both the target and the mask, by itself, had only minimal effects.     

The recognition and categorization of upright and inverted emotional expressions by 7-month-old infants

Upright and inverted faces were used to determine whether 7-month-old infants discriminate emotional expressions on the basis of affectively relevant information. In Experiment 1, infants recognized the similarity of happy faces over changing identities and discriminated this expression from fear and anger when the stimuli were presented upright, but not when they were inverted. In Experiment 2, infants were able to discriminate happiness from fear and anger posed by a single model, regardless of the orientation of the stimuli. From these studies it was suggested that categorizing emotional expressions depends upon attending to affectively relevant, orientation-specific information, whereas the discrimination of emotional expressions can be done on a featural basis, something that remains invariant regardless of the orientation of the stimuli. In Experiment 3, infants discriminated toothy happiness posed by several models from nontoothy happiness and nontoothy anger when the stimuli were presented upright and inverted. Thus, when salient features were available, the infants based their discriminations on perceptual aspects rather than on conceptual aspects such as categories of emotions.