Prototypes in category learning: The effects of category size, category structure, and stimulus complexity.

Although research in categorization has sometimes been motivated by prototype theory, recent studies have favored exemplar theory. However, some of these studies focused on small, poorly differentiated categories composed of simple, 4-dimensional stimuli. Some analyzed the aggregate data of entire groups. Some compared powerful multiplicative exemplar models to less powerful additive prototype models. Here, comparable prototype and exemplar models were fit to individual-participant data in 4 experiments that sampled category sets varying in size, level of category structure, and stimulus complexity (dimensionality). The prototype model always fit the observed data better than the exemplar model did. Prototype-based processes seemed especially relevant when participants learned categories that were larger or contained more complex stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Female choice and manipulations of forceps size and symmetry in the earwig Forficula auricularia L

Nutrition influences the reproductive axis via alteration of gonadotrophin secretion. However, a link between nutrition and the secretion of GnRH, which drives the axis, has yet to be established. The aim of the present study was to measure the change in the concentrations of metabolic substances in the cerebrospinal fluid of adult male sheep offered a diet designed to maintain constant gonadotrophin secretion (Group M; n = 6), or a diet known to increase gonadotrophin secretion (Group M + L; n = 6). On days 1, 3 and 10 of the dietary treatments, cerebrospinal fluid and jugular blood were sampled and analysed for metabolic fuels (glucose, amino acids and free fatty acids) and metabolic hormones (insulin, insulin-like growth factor I, GH, prolactin, cortisol and the thyroid hormones). On day 11 of the dietary treatment, LH pulse frequency and mean FSH concentrations in Group M + L had increased relative to Group M and to day 0. Plasma concentrations of prolactin and insulin on days 3 and 10, and glucose and insulin-like growth factor I on day 10, were higher in Group M + L than in Group M, but only cerebrospinal fluid concentrations of insulin, glucose and certain amino acids were affected by the dietary treatments on days 3 and 10. Cerebrospinal fluid, but not plasma, concentrations of aspartate, tyrosine, cystine, phenylalanine and arginine on day 3, and glutamine, gamma-aminobutyric acid, threonine, alanine on days 3 and 10, were higher in Group M + L relative to Group M. On day 10, plasma and cerebrospinal fluid concentrations of arginine, phenylalaine, proline, tyrosine, methionine and phosphoserine, but only the plasma concentrations of linoleic acid, aspartate and serine, were higher in Group M + L than in Group M. Concentrations of triiodothyronine, thyroxine, and cortisol in plasma and cerebrospinal fluid were not affected. These results show that the nutritional stimulation of gonadotrophin secretion is accompanied primarily by fluctuations in plasma and cerebrospinal fluid concentrations of insulin and certain amino acids, which suggests that, when nutritional status is improved, insulin, amino acids and possibly glucose interact to modulate GnRH secretion.     

The changing world of organization change.

Characterizes the changing world of organization change (OC) in the following ways: from growth to decline to consolidation, from moderate to high speed, from complexity to even greater complexity, and from naive clients to sophisticated ones who can use the term culture change before the consultant does. Aspects of change regarding human behavior in organizations are stable (i.e., grounded in theory and research). Two conclusions about organization consulting today are identified: There is a set of standard tools that effectively addresses small to medium-size problems in organizations. Consultants are on the threshold of a paradigm for the effective management of large-scale OC. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The category effect with rating scales: Number of categories, number of stimuli, and method of presentation.

Four experiments were conducted, using approximately 500 undergraduates, to compare category ratings of sets of stimuli with different skewing (i.e., positive and negative) under different conditions. Results indicate that squares received higher category ratings when the smaller sizes were presented more frequently than the larger sizes. This shift in the rating scale was greater when there were either fewer categories (the category effect) or more stimuli. Similar shifts were obtained whether the stimuli were presented successively for judgment or simultaneously. The category effect also occurred when Ss were not told how many categories to use until after the contextual stimuli had been presented. It is suggested that a simple range-frequency model describes most of the shifts in scale by variations in a single weighting parameter. However, these shifts are predicted by an elaborated model in which the number of representations of any stimulus in working memory is limited by a principle of consistent assignment of each stimulus to a single category. It is concluded that this elaborated model correctly predicts the disappearance of the category effect when contexts are manipulated by varying the spacing of stimulus values rather than by varying their relative frequencies. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stages of change and decisional balance for 12 problem behaviors.

Investigated the generalization of the transtheoretical model across 12 problem behaviors. The cross-sectional comparisons involved relationships between 2 key constructs of the model, the stages of change and decisional balance. The behaviors studied were smoking cessation, quitting cocaine, weight control, high-fat diets, adolescent delinquent behaviors, safer sex, condom use, sunscreen use, radon gas exposure, exercise acquisition, mammography screening, and physicians' preventive practices with smokers. Clear commonalities were observed across the 12 areas, including both the internal structure of the measures and the pattern of changes in decisional balance across stages. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Postclassification category use: The effects of learning to use categories after learning to classify.

The use of category knowledge can affect category representations, including classification knowledge, even if people learn to classify before learning to use the categories. In 5 experiments, subjects first learned to classify spy messages and then learned a category use that required simple problem solving (applying a formula to decode a message). The number relations that were important for the decoding were later used as an additional basis of classification. This effect of category use occurred even when the classification was not provided during use learning, if the category representation was incidentally available. This incidental activation of the category representation is common in real-world situations and can occur by additional processing (Experiment 2) or by extended classification learning (Experiments 3–5). The discussion focuses on the conditions necessary for obtaining this effect and the generality of the findings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Freedom of choice and behavioral change.

Used a 3?×?2 (Treatment?×?Population) factorial design with repeated measures (pretest/posttest) to evaluate the effects of perceived freedom of choice on behavior change in a therapy analog study. 90 Ss were assigned to 3 groups that varied in the amount of perceived choice given to Ss in determining the type of training procedure used for speed-reading enhancement. Experimental conditions were crossed with 2 populations of Ss to examine 2 levels of perceived freedom. Half of the Ss were psychology undergraduates required to participate in psychology experiments, and the remaining half were volunteers. The main dependent variable was the amount of change in reading rate. A marginally significant increase in reading speed was obtained by volunteers in comparison to psychology student participants. Ss who perceived that they were given a choice in training procedures improved significantly more in reading speed than Ss who lost the freedom of choice. No changes in reading comprehension were noted. Findings are discussed in terms of the relationship between freedom of choice and performance in a behavior change program. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The roles of typicality, instance dominance, and category dominance in verifying category membership.

Examined the relationships between category verification reaction time (RT), exemplar typicality, instance dominance, category selection time (an RT measure of category dominance), and 3 production measures of category dominance in 3 experiments with 122 Ss. The category dominance measures were obtained in Exp I for use in 2 nearly identical category verification experiments. In Exp II, the category name was presented 800 msec before the exemplar name. In Exp III, the exemplar name preceded the category name by 800 msec. Multiple regression analyses of the yes and no category verification RTs indicated that category dominance produced large and highly significant effects in all conditions, whereas instance dominance produced marginally significant and selective effects. Typicality had no effect beyond its shared effect with the dominance measures except as a possible suppressor variable. Category selection time was the best predictor, although all of the category dominance measures were better predictors than typicality or instance dominance. It is concluded that typicality may be an inappropriate independent variable for RT tasks studying the memory representation of natural-world knowledge. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of group size, problem difficulty, and sex on group performance and member reactions.

Examined the influence of group size, task difficulty, and member sex on the relationship between actual productivity and potential productivity proposed by I. D. Steiner (1972), and tested the predictive accuracy of hierarchical and equalitarian latency models proposed by F. Restle and J. H. Davis (1962). 349 undergraduates worked 3 intellectual problems of varying difficulty, either as individuals or in same-sex groups of 2, 3, 6, and 10 members. Actual performance was assessed using indexes of the proportion of solvers and time to solution. Potential performance scores were generated from theoretical models for the same indexes. Group size and problem difficulty were important determinants of group performance, whereas member sex generally was not. Size and difficulty effects varied depending on choice of performance measure. For the proportion index, groups often worked up to potential, but those same groups usually fell below potential on the latency index; they were effective but inefficient. Group performance on both indexes generally fell below potential as size and difficulty increased. The concept of "functional size" is advanced to explain the observed pattern of group performance: As group size increases the number of nonparticipators also increases, resulting in a functional group size smaller than actual size. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrophysiological, behavioral, and subjective indexes of workload when performing multiple tasks: manipulations of task difficulty and training

This study examined whether alpha event-related desynchronization (ERD) and theta event-related synchronization (ERS) could successfully measure changes in cognitive workload and training while an operator was engaged in a continuous, interactive, control task(s). Alpha 1 (8-10 Hz) ERD, alpha 2 (10-12 Hz) ERD, and theta (3-7 Hz) ERS were determined for a communications event that occurred during multiple task workload conditions or as a single task. Other measures (alpha and theta EEG power, heart rate, respiration, eye blinks, behavioral performance, and subjective workload ratings) were also evaluated. Results showed that alpha 2 EEG, heart rate, behavioral, and subjective measures were sensitive to changes in workload in the multiple tasks. In addition, eye blink rate and behavioral measures were sensitive to training. Alpha ERD and theta ERS were not sensitive to workload and training in our interactive, multiple task environment. However, they were effective indexes of cognitive/behavioral demands within an interactive single task.     

Test difficulty, reliability, and discrimination as functions of item difficulty order.

In an attempt to evaluate the often stated rule that test items should be arranged in an increasing order of difficulty, the effect of item difficulty order on total test reliability, difficulty, and discrimination was investigated in a series of 4 experiments. Each experiment involved a comparison of 2 or more tests, containing the same 40 items and differing only with respect to the order of those items. The differently ordered forms did not, in any of the experiments, differ significantly in test difficulty or test reliability. The results with respect to discrimination were not as clear-cut. However, the results tend to lead to the conclusion that item difficulty order on a power test of facts and principles given in the normal college classroom will not significantly affect these 3 test statistics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prior knowledge: The effects of natural category size on memory for implicitly encoded concepts.

Studying a familiar word activates its associates, and these associates affect the likelihood of recalling the studied word in a cued recall task. These experiments examined variables that normally affect memory for the studied word to determine if they have similar effects on memory for the word's associates. Memory for associates was tested by cued recall (Experiments 1–3) or by recognition (Experiments 4–5), with the number and strength of the associates varied in all experiments. In different experiments, test instructions (direct–indirect), distractor tasks, lag, and amount of practice were manipulated. Provided that subjects were not distracted prior to test, the probability of recalling associates of the studied word decreased with the number of associates activated and with their strength under all conditions. The strength of the associates but not their number affected recognition. In general, variables that affected recall and recognition of studied words had parallel effects on their associates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Encoding context and retrieval conditions as determinants of the effects of natural category size.

Studying a familiar word activates its associates in long-term memory. In the present experiments we manipulated the number of associates activated by words studied in the presence of unrelated context words, meaningfully related context words, or in the absence of modifying context words. Memory was tested by either cued or free recall. The results showed that the number of directly activated associates can facilitate, have no effect, or disrupt recall for studied words. The direction and magnitude of the effects of number of activated associates is shown to be determined by the encoding/retrieval context. Implications for the distinction between episodic and semantic memory are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Additivity and interaction between size ratio and response category in the comparison of size-discrepant shapes.

In Experiment 1, subjects made same–different judgments to pairs of shapes that could differ (irrelevantly) in size and in which different pairs combined distinct shapes. Size discrepancy had an effect both on same and different responses. It is argued that this nonmonotonicity was produced by a form of bias acting to slow different responses for same-sized pairs. Consistent with the proposed bias account, the nonmonotonic size-discrepancy effect on different trials was eliminated in Experiment 2, in which trials were blocked by size ratio. In Experiment 3, subjects performed a task similar to that in Experiments 1 and 2. However, additional visual information was added inside the bounding contour of the shapes, and this information was either the same or different across shapes. The match between within-contour information across shapes (whether same or different) was varied orthogonally with whether the bounding contours of the shapes were the same or different. In this experiment subjects decided whether the bounding contours of the shapes were the same or different, while ignoring the added information within the contours. When the added information matched across the two shapes, same responses were facilitated relative to when the added information mismatched. The converse occurred for different responses. This effect was more pronounced when the shapes were shown at the same size than when the shapes were at different sizes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The changing workforce, job stress, and psychological distress.

The change in the United States from a manufacturing economy to a service economy has important implications for theoretical models of the relationships between job characteristics and workers' psychological distress. A sample of 600 men and women employed full-time were recruited to test 2 theoretical models. The job demand-control model posits that jobs that are both high in job demands and low in decision latitude are associated with greater psychological distress. The job demand-service model posits that jobs that are high in job demands and low in service to others are associated with greater psychological distress. Results show that the job demand-control model is a significant predictor of psychological distress among employees in the manufacturing industry, whereas the job demand-service model is a significant predictor of psychological distress among employees in the services industries. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of difficulty and diagnosticity on choice among tasks in relation to achievement motivation and perceived ability.

Replicated Y. Trope's (see record 1976-09902-001) study, by investigating the effects of 2 person characteristics (achievement motivation and perceived own ability) and 2 task characteristics (difficulty and diagnostic value about own ability) on choice among achievement tasks. Ss were 104 male high school students. In accordance with the results of Trope, it was found that high-diagnostic tasks were preferred to low-diagnostic tasks, independent of their difficulty. Trope's finding that high resultant achievers choose high-diagnostic tasks over low-diagnostic tasks to a greater extent than low resultant achievers was not replicated. The perceived degree of own ability affected choice behavior: When easy and difficult tasks were both high in diagnosticity, Ss high in perceived ability preferred difficult over easy tasks, whereas Ss low in perceived ability preferred easy over difficult tasks. It is concluded that a self-informational conception of choice behavior has to include the subjective probability of success at tasks as a determinant of choice, in addition to objective difficulty and diagnostic value. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of goal difficulty on physiological arousal, cognition, and task performance.

Conducted 2 laboratory experiments with 117 undergraduates to examine (1) the effect of assigned goal difficulty on arousal (self-report and heart rate), cognition (perceived norm, self-efficacy strength, and personal goal), and behavioral (task performance) measures and (2) the role of heart rate as a mediator of the goal-difficulty–performance relation. All Ss performed a task requiring cognitive and physical responses. Results of both experiments demonstrate that assigned goal difficulty affected heart rate, cognition, and task performance and that heart rate change was positively related to the cognitive and behavioral measures. Regression analyses suggested that a cognitive–affective mechanism may mediate the goal-difficulty–performance relation. Discussion is focused on the theoretical and practical implications of integrating an arousal concept within goal-setting theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motivation, anxiety, and the difficulty of avoidant control.

Examined in 105 male undergraduates, whether avoidant control that was difficult to exercise induced greater physiologic arousal and unpleasant affect than easy-avoidant control or no-avoidant control. Two types of control difficulty were distinguished and factorially varied: control difficulty due to the effortfulness of a controlling activity and control difficulty due to uncertainty about how to exercise control over an unpleasant outcome. To examine responses under conditions where avoiding an unpleasant event is impossible, a cell was included in which Ss were not given the means by which to exercise control. In all but 1 condition, when avoidance was expected to be easy or impossible (a) pulse rates were lower, (b) digital pulse volumes were higher, (c) self-reported anxiety was lower, and (d) ratings of the stressor's unpleasantness were lower than they were when avoidance was expected to be difficult. In the high-effort-exercise/high-response-uncertainty condition, cardiovascular arousal, self-reported anxiety, and shock umpleasantness scores were relatively low, suggesting that control was sufficiently difficult in that condition to cause Ss to give up. Results are discussed in terms of a model of motivation (J. W. Brehm), conceptions of anxiety, and the relation between stress and control. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Values, valences, and choice: The influences of values on the perceived attractiveness and choice of alternatives.

Hypotheses about relations between values, valences, and choice were tested in a study in which 239 university students completed the Schwartz Value Survey (S. H. Schwartz, 1992) and then responded to 10 hypothetical scenarios, each of which presented them with 2 alternative courses of action assumed to prime different value types from the Schwartz circular structure. For each scenario, participants rated the attractiveness or valence of each alternative and then indicated which one they would choose. Results showed that, as predicted, valences were related to value types, and choice of alternative was a function of both value types and valences. The pattern of relations was consistent with the assumption that values may induce valences on potential actions and outcomes and that value types may be organized into 2 bipolar dimensions, one of which contrasts openness to change with conservation and the other of which contrasts self-enhancement with self-transcendence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Similar and different: The differentiation of basic-level categories.

Categories in the middle level of a taxonomic hierarchy tend to be highly differentiated in that they have both high levels of within-category similarity and low levels of between-category similarity. Research on similarity reveals a distinction between pairs of categories that are seen as dissimilar because they have few commonalities and pairs that are seen as dissimilar because they have many psychologically relevant alignable differences. The authors suggest that the low between-category similarity proposed for neighboring basic-level categories is actually a matter of having many psychologically relevant differences. In contrast, the low between-category similarity of superordinates is a result of their having few commonalities. The authors evaluate this claim in 4 experiments using a variety of natural stimuli and converging measures. The data support the importance of alignable differences for distinguishing between pairs of basic-level categories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)