Array models for category learning

A family of models for category learning is developed, all members being based on a common memory array but differing in memory access and decision processes. Within this framework, fully controlled comparisons of exemplar-similarity, feature-frequency, and prototype models reveal isomorphism between models of different types under some conditions but empirically testable differences under others. It is shown that current exemplar-memory models, in which categorization judgments are based on similarities of perceived and remembered category exemplars, can be interpreted as generalized likelihood models but can be modified in a simple way to yield pure similarity models. Distance-based exemplar models are formulated that provide means of investigating issues concerning deterministic versus probabilistic decision rules and links between categorization and properties of perceptual dimensions. Other theoretical issues discussed include aspects of similarity, the role of memory storage versus computation in category judgments, and the limits of applicability of array models.     

Emotion and memory: A recognition advantage for positive and negative words independent of arousal

Much evidence indicates that emotion enhances memory, but the precise effects of the two primary factors of arousal and valence remain at issue. Moreover, the current knowledge of emotional memory enhancement is based mostly on small samples of extremely emotive stimuli presented in unnaturally high proportions without adequate affective, lexical, and semantic controls. To investigate how emotion affects memory under conditions of natural variation, we tested whether arousal and valence predicted recognition memory for over 2500 words that were not sampled for their emotionality, and we controlled a large variety of lexical and semantic factors. Both negative and positive stimuli were remembered better than neutral stimuli, whether arousing or calming. Arousal failed to predict recognition memory, either independently or interactively with valence. Results support models that posit a facilitative role of valence in memory. This study also highlights the importance of stimulus controls and experimental designs in research on emotional memory.     

On the communication of information by displays of standard errors and confidence intervals

A survey of practices regarding the presentation of information about reliability of means in psychological research publications over the last century reveals some advance in quality of communication, greater for tabular presentations than for graphic presentations, but also substantial room for improvement. In this article, problems of interpretation and communication associated with presentations of standard errors and confidence intervals in research reports are examined from both statistical and psychological perspectives. Four general principles of effective communication are proposed and illustrated in application to presentations of data from common psychological research designs, with special attention to problems arising in connection with repeated measures.     

Efficacy of awareness of strategy and overt verbalization for recall by kindergarten students.

Two prevailing models for teaching memory strategies for remembering were compared for two kindergarten classes (45 boys, 30 girls). A third class provided a control. One class received instruction in specific and efficacious strategies for recall on three discrete tasks: sequential memory, paired-associate memory, and clustering recall. The second class received the same instruction embedded in an overt verbalization procedure adapted form Bash and Camp (1985). The control class received as much practice as the two instructional groups but no instruction on strategy or overt verbalization. Significant gains in memory were made on paired associates at posttest for both the strategy-only group and the overt-verbalization group. Overt verbalization inhibits recall on paired associates at delayed posttest and its effect on sequential memory at posttest remains equivocal.     

Visual detection in relation to display size and redundancy of critical elements I

Visual detection was studied in relation to displays of discrete elements, randomly selected consonant letters, distributed in random subsets of cells of a matrix, the S being required on each trial to indicate only which member of a predesignated pair of critical elements was present in a given display. Experimental variables were number of elements per display and number of redundant critical elements per display. Estimates of the number of elements effectively processed by a S during a 50 ms. exposure increased with display size, but not in the manner that would be expected if the S sampled a fixed proportion of the elements present in a display of given area. Test-retest data indicated substantial correlations over long intervals of time in the particular elements sampled by a S from a particular display. Efficiencies of detection with redundant critical elements were very close to those expected on the hypothesis of constant sample size over trials for any given display size and were relatively invariant with respect to distance between critical elements.     

Comparison and contrast in perceptual categorization

People categorized pairs of perceptual stimuli that varied in both category membership and pairwise similarity. Experiments 1 and 2 showed categorization of 1 color of a pair to be reliably contrasted from that of the other. This similarity-based contrast effect occurred only when the context stimulus was relevant for the categorization of the target (Experiment 3). The effect was not simply owing to perceptual color contrast (Experiment 4), and it extended to pictures from common semantic categories (Experiment 5). Results were consistent with a sign-and-magnitude version of N. Stewart and G. D. A. Brown's (2005) similarity-dissimilarity generalized context model, in which categorization is affected by both similarity to and difference from target categories. The data are also modeled with criterion setting theory (M. Treisman & T. C. Williams, 1984), in which the decision criterion is systematically shifted toward the mean of the current stimuli.     

Reaction time in relation to display size and correctness of response in forced-choice visual signal detection

Response times were recorded in a two-alternative, forced choice visual detection situation. Stimulus displays, presented tachistoscopically, were randomly selected consonant letters distributed in random subsets of cells of a matrix. Display sizes in Experiment I were 8, 12, and 16 letters; in Experiment 2–1, 4, and 8 letters; on each trial S operated a key to indicate which member of a predesignated pair of letters (signal elements) was present in a given display. Correct response times, on the average, increased uniformly with display size. Incorrect response times were uniformly greater than correct response times and, except for a reduction in the case of one element displays, were constant over display size. These relationships appear to require a modification of one assumption in the earlier proposed serial processing model for tachistoscopic perception.     

Reaction time in relation to display size and correctness of response in forced-choice visual signal detection

Response times were recorded in a two-alternative, forced choice visual detection situation. Stimulus displays, presented tachistoscopically, were randomly selected consonant letters distributed in random subsets of cells of a matrix. Display sizes in Experiment 1 were 8, 12, and 16 letters; in Experiment 2—1, 4, and 8 letters; on each trial S operated a key to indicate which member of a predesignated pair of letters (signal elements) was present in a given display. Correct response times, on the average, increased uniformly with display size. Incorrect response times were uniformly greater than correct response times and, except for a reduction in the case of one element displays, were constant over display size. These relationships appear to require a modification of one assumption in the earlier proposed serial processing model for tachistoscopic perception.     

Further evidence concerning scanning and sampling assumptions of visual detection models

Following extended training in a visual detection task, functions were determined for individual Ss relating latency of detection responses to number of redundant signal elements embedded in tachistoscopic displays of letters and to distance between signal elements. Latency proved invariant with respect to number of redundant signals and varied non-monotonically with distance. Of the several types of models considered in relation to previous studies, substantial support was forthcoming only for an independent stimulus sampling model. It is suggested that the detection method effects a relatively clear separation of the perceptual from the mnemonic aspects of the standard visual apprehension experiment, and that the sampling process may constitute only the first phase of a more general model which includes both parallel and serial information processing.