Integrating information from separable psychological dimensions.

This article examines decision processes in the perception and categorization of stimuli composed of the separable psychological dimensions, orientation and size. The randomization technique (F. G. Ashby and R. Gott; see record 1989-07388-001) of general recognition theory, which allows accurate estimation of a subject's decision boundary in a categorization task, is used in 4 experiments. Even though the stimulus components are clearly separable, it was found that Ss were not constrained to use separable response strategies, nor were they constrained to attend to distance to the prototypes. Instead, they used decision rules that were nearly optimal, even if this required information integration or for the Ss to attend to higher level category properties such as component correlation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Base-rate effects in multidimensional perceptual categorization

The optimality of human performance when category base rates differ was investigated in 2 multidimensional perceptual categorization tasks. All participants were sensitive to differences in base rate, even during their 1st experimental session. Nearly half of the participants learned the optimal decision bound by their final experimental session. Little evidence for conservative cutoff placement was found (i.e., an underestimation of category base-rate differences). In fact, participants who did not learn the optimal decision bound tended to use a decision bound that overestimated the base-rate difference. Across all conditions participants showed a clear shift toward the optimal decision bound with experience. These data suggest that experienced participants are highly sensitive to differences in category base rate. The model-based analyses suggest that the decision-bound model of categorization (Ashby, 1992a; Ashby & Maddox, 1993; Maddox & Ashby, 1993) provides a powerful tool for investigating the limits of human categorization performance.     

Suboptimality in human categorization and identification.

Categorization and identification decision processes were examined and compared in 4 separate experiments. In all tasks, the critical stimulus component was a line that varied across trials in length and orientation, and the optimal decision rules were always complex piecewise quadratic functions. Evidence was found that identification is mediated by separate explicit and implicit systems. In addition, a common type suboptimality was found in both categorization and identification. In particular, observers apparently approximated the piecewise quadratic functions of the optimal decision rules with simpler piecewise linear functions. A computational model, which was motivated by a recent neuropsychological theory of category learning, successfully accounted for this suboptimal performance in both categorization and identification. The model assigns a key role to the striatum and assumes the observed suboptimality was largely due to massive convergence of visual cortical cells onto single striatal units. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transfer of the effects of verbal conditioning.

Experimental Ss were verbally conditioned to use more future tense responses in making up sentences. Transfer effects were assessed using a 2nd sentence completion task containing certain stimulus cues present on the original task. Transfer of learning was demonstrated on the basis of a grossly defined, 2-step gradient of similarity of stimulus cues contained on the learning and transfer tasks. The variables of S's awareness and S's sex did not lead to statistically significant between-group differences. The response form (written vs. oral) also failed to demonstrate a significant effect. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distinguishing common and task-specific processes in word identification: A matter of some moment?

The same 500 words were presented in 6 different word identification tasks (Experiment 1: lexical decision, semantic categorization, and 3 speeded naming tasks; Experiment 2: delayed naming). Reaction time (RT distributions were estimated for each task and analyses tested for the effects of word frequency and animacy on various parameters of the RT distribution. Low frequency words yielded more skewed distributions than high frequency words in all tasks except delayed naming. The differential skew was most marked for tasks that required lexical discrimination. The semantic categorization task yielded highly skewed distributions for all words, but the word frequency effect was due to shifts in the location of the RT distributions rather than changes in skew. The results are used to evaluate the relative contributions of a common lexical access process and task-specific processes to performance in lexical discrimination and naming tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unities in inductive reasoning.

Three experiments determined the sources of communalities in performance on 3 inductive reasoning tasks: analogies, series completions, and classifications. In Exp I, 30 undergraduates completed an untimed pencil-and-paper test in which they were asked to solve 90 induction items with names of mammals as content. Items were equally divided among the 3 kinds of induction tasks. Ss' task was to rank order 4 response options in terms of their goodness of fit as completions for each particular item. Data sets for the 3 tasks were highly intercorrelated, and a single exponential model of response choice provided a good fit to each data set. In Exp II, 36 Ss completed a timed test in which they were asked to solve 90 mammal-name induction items. Items were again equally divided among the 3 kinds of tasks. Ss' task was to choose the better of 2 response options as a completion for each particular item. Data sets for the tasks were again highly intercorrelated, and a single linear model of response times provided a good fit to each data set. In Exp III, 18 Ss were timed while solving 1,440 induction items with schematic picture, verbal, and geometric content. Items were approximately equally divided among the 3 kinds of tasks. Both analysis of stimulus and of S variance supported the notion of highly related performance algorithms on the 3 tasks. It is concluded that a common or highly similar model of response choice and of information processing can account for at least some of the previously observed relationships in performance across induction tasks. (59 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of affect on categorization.

Four studies with 256 undergraduates showed that positive affect, induced in any of 3 ways, influenced categorization of either of 2 types of stimuli—words or colors. As reflected by performance on 2 types of tasks (rating and sorting), Ss in whom positive affect had been induced tended to create and use categories more inclusively than did Ss in a control condition. On one task, they tended to group more stimuli together, and on the other task they tended to rate more low-prototypic exemplars of a category as members of the category. Results are interpreted in terms of an influence of affect on cognitive organization or on processes that might influence cognitive organization. It is suggested that borderline effects of negative affect on categorization, obtained in 2 of the studies, might result from normal people's attempts to cope with negative affect. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Generalization from categorical memory tasks to prose by learning disabled adolescents.

Investigated how 60 learning disabled ([LD] aged 12 yrs to 14 yrs 5 mo) and 20 age-matched nondisabled (NLD) Ss would transfer the use of 4 study rules from instructed materials (pictures) to a prose recall task. Four phases spread over a 3-wk period were involved: pretest, informational phase (2 lessons), individualized training (3 lessons), and posttest. Results show that LDs performed poorly relative to NLD peers at pretest on categorical picture and prose recall tasks. 20 LD Ss who received rule-only instruction and 20 LD Ss who received rule-plus-prose examples instruction surpassed 20 LD Ss in the control condition at posttest on the picture task in rule use and in recall. On the prose task, a majority of the instructed LD Ss demonstrated transfer of the instructed rules. As a group, the instructed LD Ss no longer differed observably from NLD Ss in recall or in the strategies they employed to study and to retrieve. The clinical view that LD Ss are characterized by a failure to generalize was not supported by these findings. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Categorization of individuals on the basis of multiple social features.

Five experiments used a name-matching paradigm developed by S. E. Taylor et al (1978) to investigate how people use the immediately apparent features of others as a basis of social categorization. Ss were more likely to categorize targets according to their sex than their race but also tended to categorize using a single subordinate category that represented sex and race simultaneously. Racially prejudiced Ss categorized to greater degree by race than did nonprejudiced Ss, but manipulations of construct accessibility and processing goals did not influence categorization by race or sex. Processing goals did influence the use of clothing style as a categorization feature. Results are discussed in terms of the functional utility of person features as a basis of categorization and the effects of categorization on social stereotyping and prejudice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Category learning deficits in Parkinson's disease.

Sixteen patients with Parkinson's disease (PD), 15 older controls (OCs), and 109 younger controls (YCs) were compared in 2 category-learning tasks. Participants attempted to assign colored geometric figures to 1 of 2 categories. In rule-based tasks, category membership was defined by an explicit rule that was easy to verbalize, whereas in information-integration tasks, there was no salient verbal rule and accuracy was maximized only if information from 3 stimulus components was integrated at some predecisional stage. The YCs performed the best on both tasks. The PD patients were highly impaired compared with the OCs, in the rule-based categorization task but were not different from the OCs in the information-integration task. These results support the hypothesis that learning in these 2 tasks is mediated by functionally separate systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Functional properties of primate putamen neurons during the categorization of tactile stimuli

We used psychometric techniques and neurophysiological recordings to study the role of the putamen in somesthetic perception. Four monkeys were trained to categorize the speed of moving tactile stimuli. Animals performed a task in which one of two target switches had to be pressed with the right hand to indicate whether the speed of probe movement across the glabrous skin of the left, restrained hand was low or high. During the task we recorded the activity of neurons in the putamen contralateral (right) and ipsilateral (left) to the stimulated hand. We found different types of neuronal responses, all present in the right and left putamen. Some neurons responded during the stimulus period, others responded during the hand-arm movement used to indicate categorization, and others responded during both of these periods. The responses of many neurons did not vary either with the speed of the stimuli or in relation to the categorization process. In contrast, neurons of a particular type responded differentially: their activity reflected whether stimulus speed was low or high. These differential responses occurred during the stimulus and hand-arm motion periods. A number of the nondifferential and differential neurons were studied when the same stimuli used in the categorization task were delivered passively. Few neurons with nondifferential discharges, and none of the differential neurons, responded in this condition. In a visually cued control task we studied the possibility that the differential responses were associated with the intention to press or with the trajectory of the hand to one of the target switches. In this condition, a light turned on instructed the animal which target switch to press for a reward. Very few neurons in both hemispheres maintained the differential responses observed during the categorization task. Those neurons that discharged selectively for low or high speeds were analyzed quantitatively to produce a measure comparable with the psychometric function. The thresholds of the resulting neurometric curves for the neuronal populations were very similar to the psychometric thresholds. The activity of a large fraction of these neurons could be used to accurately predict whether the stimulus speed was low or high. The results indicate that the putamen, both contralateral and ipsilateral to the stimulated hand, contains neurons that discharge in response to the somesthetic stimuli during the categorization task. Those neurons that respond irrespective of the stimulus speed appear to be involved in the general sensorimotor behavior of the animal during the execution of the task. The results suggest that the putamen may play a role in bimanual tasks. The recording of neurons in the right and left putamen whose activities correlate with the speed categories suggests that this region of the basal ganglia, in addition to its role in motor functions, is also involved in the animal's decision process.     

Cognitive development and role-taking ability in boys and girls from 7 to 12.

10 males and 10 females at each of 3 age levels (7, 9, and 12 yrs), matched on IQ, were given a social role-taking task and 2 Piagetian tasks. Performance on all tasks generally increased with age, but correlations between performances on the 2 types of tasks were generally not significant. There were no significant sex differences on the tasks. IQ was correlated with performance on the role-taking task but not with the Piagetian tasks, which were not highly correlated with each other. The ability to "think about possibilities" did not differ significantly for the age or sex groups, but this ability was significantly related to performance on the experimental tasks for the younger Ss. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Categorization as a preferred memory strategy: Developmental changes during elementary school.

20 2nd, 20 4th, and 20 6th graders (a) judged the relative effectiveness of 4 memory strategies (looking, naming, rehearsing, and categorizing) and (b) studied and recalled sets of stimuli. The order of tasks was counterbalanced within grade. Ss in all grades chose rehearsal and categorization over looking or naming. Second graders in both conditions and 4th graders who did the memory tasks first judged rehearsal and categorization as equally effective. Fourth graders who made strategy judgments first and 6th graders in both conditions significantly preferred categorization over rehearsal. On the memory task, 4th graders who judged strategy effectiveness prior to doing the memory tasks recalled more than those doing the memory task first. There was no difference due to condition for the other 2 grades. Degree of strategic awareness was related to recall only for children who made the strategy judgment prior to doing the memory tasks. Findings illustrate developmental changes in awareness of the relative benefits of categorization over rehearsal during elementary school and suggest that performance on a memory task may be affected by the degree to which appropriate metamemorial awareness is "activated." (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Speeded tests of implicit knowledge.

Three experiments tested the hypothesis that implicit and explicit tasks involve distinct modes of processing. Ss observed rule-ordered letter strings and were asked either to memorize the strings or to try to discover the underlying rules. In Exp 1, they then made well-formedness judgments of novel strings under long-deadline and short-deadline conditions. Rule-discovery Ss, but not memory Ss, were impaired by the short deadline. In Exp 2, all Ss made "similarity" judgments of the novel strings instead of the traditional "rule-based" judgments; there were now no differences between the rule-discovery and memory groups. In Exp 3, Ss explicitly instructed in the rules were significantly more impaired under short deadlines than were memory Ss. An analysis of decision times to individual strings for the rule-trained vs memory groups also showed qualitative differences consistent with the implicit–explicit distinction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Problem solving in triads composed of varying numbers of field-dependent and field-independent subjects.

Investigated the interactive effects of situational task demands and interpersonal group environment on small group performance. High-structure and low-structure tasks were solved by 3 types of small groups: 3 field-dependent Ss; 3 field-independent Ss; and triads with both field-dependent and field-independent Ss. Ss were 231 male college students who were tested with the Group Embedded Figures Test. The lower and upper third of the test distribution were defined as field dependent and field independent, respectively, and assigned to 1 of the 3 small groups. It was hypothesized that field-dependent Ss would perform tasks more efficiently than would field-independent Ss when the task environment provided structure. This hypothesis was not supported. The field-independent Ss had the fastest completion times, whereas the field-dependent Ss had the slowest times of all. It was also hypothesized that the difference in performance attributable to task structure would be greater for field-dependent Ss than it would be for field-independent Ss. This hypothesis was supported. Results demonstrate the relative ability of field-independent Ss to solve the tasks and the potential for coalition formation within the mixed triads. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquired equivalence and distinctiveness in matching to sample by pigeons: Mediation by reinforcer-specific expectancies.

Assessed the ability of a reinforcer to mediate an association between 2 stimuli that independently predict the occurrence of that reinforcer (acquired equivalence of cues). In Exp I, 12 male White Carneaux pigeons were trained on shape (plus and circle) and color (red and green) matching-to-sample tasks. Correct responses were systematically reinforced with corn on some trials and wheat on others to establish associations between 1 stimulus from each task and a "common" outcome. Following training, Ss were transferred to a symbolic matching-to-sample task wherein a stimulus from one training task was presented as the sample, and the stimuli from the other training task were presented as comparisons. In the 1st session, experimental Ss made significantly more correct responses than controls (i.e., Ss "matched" stimuli previously associated with a common outcome). Exp II with 18 Ss replicated this acquired equivalence effect and controlled for food preference. Delayed matching-to-sample training demonstrated enhanced memory performance for Ss exposed to different reinforcement contingencies, but this effect was confined to the shape task. Results indicate that a reinforcer can serve as the basis for organizing otherwise unpaired predictive cues in memory and that animals will selectively use differential expectancies as cues for solving complex discrimination tasks, depending on the difficulty of the discrimination. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in social categorization: The influence of personal need for structure on spontaneous trait inferences.

Because 1 function of categorization is to provide structure and control to social interactions and because individuals differ in the extent to which they desire control and structure, individual differences in personal need for structure (PNS) should moderate the extent to which people categorize. Spontaneous trait inferences (STIs) were used to assess the use of traits in categorization. High-PNS Ss were more likely to form STIs and more likely to recall names of target actors in the stimulus sentences. This research provides evidence for the organization of behavioral information in person nodes in circumstances where possessing goals did not explicitly request such organization. It also provides a link between the examination of chronic sources of motivation and social categorization, perhaps the most fundamental social–cognitive variable. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On priming by a sentence context.

Previous investigations of sentence context effects (SCEs) on word-naming time have uncovered a pattern of facilitation dominance. Another finding has been that words that are more difficult to recognize in isolation display larger SCEs than easier words. The present experiments with 384 undergraduates showed SCEs to be robust and eliminated several alternative explanations. Two experiments demonstrated the appropriateness of the neutral condition used to assess facilitation and inhibition. Another showed that SCEs did not depend on the procedure used. It was shown that manipulations that were designed to affect S strategies did not change the pattern of results. In 3 experiments, an interaction between stimulus quality and content condition was obtained. The interaction replicated across 2 forms of stimulus degradation, but only 1 form increased inhibition effects as well as facilitation effects. Other inconsistencies between previous SC experiments in the magnitude of the inhibition effects observed were resolved by showing that an SC produced more inhibition in the lexical decision task than in the naming task. It was demonstrated that the 2 tasks produced different amounts of inhibition when the same stimuli were used. Sentence integration processes that occurred after lexical access appeared to be responsible for some of the inhibition observed in lexical decision tasks. (85 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)