RAP: a new framework for visual categorization

Cognitive science might almost be defined as several disciplines communicating their different perspectives on the mind, the common object of study. However, domain-specific concepts and techniques can prevent, rather than foster, a communication of viewpoints. In this article, we develop a new framework for visual categorization in which the interaction between Represented (R) information and Available (A) information determine the Potent (P) information (symbolically, R ? A approximately P). We argue and illustrate that this framework helps to establish a common language to articulate issues common to low-, mid-, and high-level vision. More importantly, we present new techniques with which to visualize the so-far elusive constructs of representation and potent information.     

Responding under time pressure: Testing two animal learning models and a model of visual categorization

Two experiments are reported, which employed a Pavlovian eyelid conditioning procedure with human participants. The experiments tested the predictions of three models of the time-course of processing under time pressure. These were the extended generalized context model (Lamberts, 1998), and two variants of the Rescorla-Wagner model (Rescorla & Wagner, 1972), which were activated in cascade mode. Reinforcement schedules in the experiments were equivalent either to an AND rule or to an XOR rule. The time available for processing the conditioned stimulus and initiating a conditioned response was manipulated by varying the interval from the onset of the conditioned stimulus to the onset of the unconditioned stimulus. The results were in accord with the predictions of one of the two variants of the Rescorla-Wagner model.     

Adaptation to statistical properties of visual scenes biases rapid categorization

The initial categorization of complex visual scenes is a very rapid process. Here we find no differences in performance for upright and inverted images arguing for a neural mechanism that can function without involving high-level image orientation dependent identification processes. Using an adaptation paradigm we are able to demonstrate that artificial images composed to mimic the orientation distribution of either natural or man-made scenes systematically shift the judgement of human observers. This suggests a highly efficient feedforward system that makes use of “low-level” image features yet supports the rapid extraction of essential information for the categorization of complex visual scenes.     

Attending to simple auditory and visual signals

Rutgers-The State University, New Brunswick, New Jersey 08903 Is the quality of information obtained from simple auditory and visual signals diminished when both modalities must be attended to simultaneously? This question was investigated in an experiment in which subjects made forced-choice judgments of the location of simple light and tone signals presented in focused- and divided-attention conditions. The data are compared with the predictions of a model that describes the largest performance decrement to be expected in the divided-attention condition on the basis of nonattentional factors. The results of this comparison suggest that the difference in performance between focused- and dividedattention conditions is attributable solely to the increased opportunity to confuse signal with noise as the number of modalities is increased. Thus, there appears to be no evidence that dividing attention between modalities affects the quality of the stimulus representations of individual light and tone signals.     

Infant temperament and information processing in a visual categorization task

This study investigates the relation between temperament and information processing in 7-month-old infants. Infant temperament was assessed on multiple dimensions, using mothers' ratings on the Infant Behavior Questionnaire (IBQ). Information processing was measured during a paired-comparison visual categorization task. Infants (N=50) were familiarized with five different pairs of visual stimuli from one category, followed by two test trials, each contrasting a novel familiar-category item with a novel out-of-category item (animals vs. vehicles). Drop-out rate in this task was within a normal range (21%). No differences in temperament were found between completers and non-completers, but high reactivity to novelty and low motor activity were positively correlated with the strength of infants' familiarization response. Group comparisons between infants scoring high and low on these two dimensions of temperament confirmed this general finding: infants high on distress to novelty and low on motor activity showed stronger familiarization responses. Furthermore, infants scoring low on motor activity showed a stronger categorization response than highly active infants. This study provides evidence that performance in a cognitive categorization task and dimensions of infant temperament are systematically related during the second half of the first year of life. Implications for cognitive research with infants of this age-range will be discussed.     

Thirty categorization results in search of a model

One category structure dominated in the shift toward exemplar-based theories of categorization. Given the theoretical burden on this category structure, the authors reanalyzed 30 of its uses over 20 years in 8 articles. The authors suggest 4 conclusions. (a) This category structure may encourage exemplar-memorization processes because of its poor structure, the learning difficulties it causes, and its small, memorizable exemplar sets. Its results may only generalize narrowly. (b) Exemplar models have an advantage in fitting these 30 data sets only because they reproduce a performance advantage for training items. Other models fit equally well if granted this capacity. (c) A simpler exemplar process than assumed by exemplar models suffices to explain these data sets. (d) An important qualitative result predicted by exemplar theory is not found overall and possibly should not even be expected. The authors conclude that the data produced by this category structure do not clearly support exemplar theory.     

Evidence of fixed capacity in visual object categorization

How is visual object perception limited by divided attention? Whereas some theories have proposed that it is not limited at all (unlimited capacity), others have proposed that divided attention introduces restrictive capacity limitations or serial processing (fixed capacity). We addressed this question using a task in which observers searched for instances of particular object categories, such as a moose or squirrel. We applied an extended simultaneous-sequential paradigm to test the fixed-capacity and unlimited-capacity models (Experiment 1). The results were consistent with fixed capacity and rejected unlimited capacity. We ascertained that these results were due to attention, and not to sensory interactions such as crowding, by repeating the experiment using a cuing paradigm with physically identical displays (Experiment 2). The results from both experiments were consistent with theories of object perception that have fixed capacity, and they rejected theories with unlimited capacity. Both serial and parallel models with fixed capacity remain viable alternatives.     

The role of visual similarity in picture categorization

Categorization is usually assumed to require access to a concept's meaning. When pictures are categorized faster than words, they are assumed to be understood faster than words. However, pictures from the same category are more similar than pictures from different categories. The present article argues that the use of visual similarity as a cue to category membership may produce the picture advantage. The visual similarity hypothesis was tested in two experiments. In the first experiment, pictures showed a disadvantage for the visually similar categories of fruits and vegetables, but showed their usual advantage for the visually dissimilar categories of fruits and animals. In the second experiment, with a mixed list design, pictures were slower only for visually similar different decisions, but showed the usual advantage for all other decisions. The reliability of visual similarity as a cue to the decision accounted well for these results. Because visual similarity can be shown to have large effects on picture categorization, the use of categorization to compare speed of understanding of pictures and words is questionable.     

Training preschool children to use visual imagining as a problem-solving strategy for complex categorization tasks

It has been suggested that verbally sophisticated individuals engage in a series of precurrent behaviors (e.g., covert intraverbal behavior, grouping stimuli, visual imagining) to solve problems such as answering questions (Palmer, 1991; Skinner, 1953). We examined the effects of one problem solving strategy--visual imagining--on increasing responses to intraverbal categorization questions. Participants were 4 typically developing preschoolers between the ages of 4 and 5 years. Visual imagining training was insufficient to produce a substantial increase in target responses. It was not until the children were prompted to use the visual imagining strategy that a large and immediate increase in the number of target responses was observed. The number of prompts did not decrease until the children were given a rule describing the use of the visual imagining strategy. Within-session response patterns indicated that none of the children used visual imagining prior to being prompted to do so and that use of the strategy continued after introduction of the rule. These results were consistent for 3 of 4 children. Within-session response patterns suggested that the 4th child occasionally imagined when prompted to do so, but the gains were not maintained. The results are discussed in terms of Skinner's analysis of problem solving and the development of visual imagining.     

Intrahemispheric differentiation of vowels: Principal component analysis of auditory evoked responses to computer-synthesized vowel sounds

Auditory evoked brain responses (AER) were recorded in response to a series of synthesized vowel sounds which varied in formant bandwidth. Multivariate analyses indicated that changes in AER component structure recorded from different scalp regions over both hemispheres varied as a function of different vowel sounds and formant bandwidth. No interhemispheric differences in scalp AER distributions were noted.     

A hybrid model of categorization

Category learning is often modeled as either an exemplar-based or a rule-based process. This paper shows that both strategies can be combined in a cognitive architecture that was developed to model other task domains. Variations on the exemplar-based random walk (EBRW) model of Nosofsky and Palmeri (1997b) and the rule-plus-exception (RULEX) rule-based model of Nosofsky, Palmeri, and McKinley (1994) were implemented in the ACT-R cognitive architecture. The architecture allows the two strategies to be mixed to produce classification behavior. The combined system reproduces latency, learning, and generalization data from three category-learning experiments--Nosofsky and Palmeri (1997b), Nosofsky et al., and Erickson and Kruschke (1998). It is concluded that EBRW and ACT-R have different but equivalent means of incorporating similarity and practice. In addition, ACT-R brings a theory of strategy selection that enables the exemplar and the rule-based strategies to be mixed.     

Using multiple-tact training to produce emergent visual categorization in children with autism

Previous research has shown that children with autism spectrum disorder (ASD) can categorize visual stimuli without direct training when they can also tact these stimuli using a common name and behave as listeners in relation to this name. However, children usually learn to assign objects specific names prior to learning the category to which they belong. The current study replicated previous research and evaluated whether multiple-tact training would establish visual categorization (measured by a picture sorting test) and listener behavior. We used a nonconcurrent multiple baseline design across 2 children with autism spectrum disorder. After multiple-tact training, we assessed whether participants would visually categorize stimuli based on their common category name. Both participants categorized and engaged in the corresponding listener behavior.     

The potentiation of grasp types during visual object categorization

The close integration between visual and motor processes suggests that some visuomotor transformations may proceed automatically and to an extent that permits observable effects on subsequent actions. A series of experiments investigated the effects of visual objects on motor responses during a categorisation task. In Experiment 1 participants responded according to an object's natural or manufactured category. The responses consisted in uni-manual precision or power grasps that could be compatible or incompatible with the viewed object. The data indicate that object grasp compatibility significantly affected participant response times and that this did not depend upon the object being viewed within the reaching space. The time course of this effect was investigated in Experiments 2–4b by using a go-nogo paradigm with responses cued by tones and go-nogo trials cued by object category. The compatibility effect was not present under advance response cueing and rapidly diminished following object extinction. A final experiment established that the compatibility effect did not depend on a within-hand response choice, but was at least as great with bi-manual responses where a full power grasp could be used. Distributional analyses suggest that the effect is not subject to rapid decay but increases linearly with RT whilst the object remains visible. The data are consistent with the view that components of the actions an object affords are integral to its representation.     

The effect of set on categorization in visual search

Two experiments examine whether set for a categorial difference or set for a target category is necessary in order to obtain the category effect in visual search. Eliminating a set for categorial difference does not diminish the size of the effect. When subjects are prevented from developing a useful set for the target category, however, the category effect is eliminated.     

An electrophysiological comparison of visual categorization and recognition memory

Object categorization emphasizes the similarities that bind exemplars into categories, whereas recognition memory emphasizes the specific identification of previously encountered exemplars. Mathematical modeling has highlighted similarities in the computational requirements of these tasks, but neuropsychological research has suggested that categorization and recognition may depend on separate brain systems. Following training with families of novel visual shapes (blobs), event-related brain potentials (ERPs) were recorded during both categorization and recognition tasks. ERPs related to early visual processing (N1, 156–200 msec) were sensitive to category membership. Middle latency ERPs (FN400 effects, 300–500 msec) were sensitive to both category membership and old/new differences. Later ERPs (parietal effects, 400–800 msec) were primarily affected by old/new differences. Thus, there was a temporal transition so that earlier processes were more sensitive to categorical discrimination and later processes were more sensitive to recognition-related discrimination. Aspects of these results are consistent with both mathematical modeling and neuropsychological perspectives.     

Using both an auditory and a visual short-term store to increase digit span

Can digit span be increased by storing digits nonredundantly in both an auditory short-term store and a visual short-term store (dual storage)? In Experiment 1, when four digits were presented visually and then the remaining digits were presented auditorily, digit span increased three digits over a baseline measurement, but only when the auditorily presented digits were reported first (inverted response). Normal order of response for this presentation was not as effective. Possible reasons for the advantage of inverted response are suggested, based upon dual storage. For all-auditory and all-visual presentations that controlled for parsing, digit span increased only 1 to 1.5 digits over baseline, and inverted and normal order of response did not differ. Experiment 2 demonstrated that an improvement for dual storage could occur when the type of presentation was held constant and the order of response was normal rather than inverted. The results are consistent with the idea of separate auditory and visual short-term stores.