Costs and benefits in perceptual categorization

Observers categorized perceptual stimuli when the category costs and benefits were manipulated across conditions, and costs were either zero or nonzero. The cost-benefit structures were selected so that performance across conditions was equivalent with respect to the optimal classifier. Each observer completed several blocks of trials in each of the experimental conditions, and a series of nested models was applied to the individual observer data from all conditions. In general, performance became more nearly optimal as observers gained experience with the cost-benefit structures, but performance reached asymptote at a suboptimal level. Observers behaved differently in the zero- and nonzero-cost conditions, performing consistently worse when costs were nonzero. A test of the hypothesis that observers weight costs more heavily than benefits was inconclusive. Some aspects of the data supported this differential weighting hypothesis, but others did not. Implications for current theories of cost-benefit learning are discussed.     

A test of the optimal classifier's independence assumption in perceptual categorization

Observers completed perceptual categorization tasks that included separate base-rate/payoff manipulations, corresponding simultaneous base-rate/payoff manipulations, and conflicting simultaneous base-rate/payoff manipulations. Performance (1) was closer to optimal for 2:1 than for 3:1 base-rate/payoff ratios and when base rates as opposed to payoffs were manipulated, and (2) was more in line with the predictions from the flat-maxima hypothesis than from the independence assumption of the optimal classifier in corresponding and conflicting simultaneous base-rate/payoff conditions. A hybrid model that instantiated simultaneously the flat-maxima and the competition between reward and accuracy maximization (COBRA) hypotheses was applied to the data. The hybrid model was superior to a model that incorporated the independence assumption, suggesting that violations of the independence assumption are to be expected and are well captured by the flat-maxima hypothesis without requiring any additional assumptions. The parameters indicated that observers' reward-maximizing decision criterion rapidly approaches the optimal value and that more weight is placed on accuracy maximization in separate and corresponding simultaneous base-rate/payoff conditions than in conflicting simultaneous base-rate/payoff conditions.     

ANALYSIS OF WORK GROUP PRODUCTIVITY IN AN APPLIED SETTING: APPLICATION OF A TIME SERIES PANEL DESIGN

We provide a demonstration of a time series panel analysis applied under typical field research conditions characterized by (a) a small number of groups (b) all of which experience an intervention (thus there is no traditional control group), and (c) perform noncomparable tasks. The time series techniques allow a direct test of Naylor, Pritchard, and Ilgen's (1980) theory of behavior in organizations applied to work group productivity in a large-scale study of work groups conducted by Pritchard and colleagues (1989). The responses of 5 work groups to priority scores for 37 indicators of productivity over 23 months were used to predict month-by-month changes in productivity for each of the 37 group products. The results show that group productivity improvements can be explained by feedback including priority scores derived from nonlinear contingency functions of the productivity indicators. Furthermore, groups differed in their response to priority feedback. Goal setting positively affected productivity gain consistently across work groups, after the effects of priority feedback and the interaction of work groups with priority feedback were accounted for. Implications for group performance strategies and appropriate applications of the time series panel analysis are discussed.     

Observational versus feedback training in rule-based and information-integration category learning

The effects of two different kinds of categorization training were investigated. In observational training, observers are presented with a category label and then shown an exemplar from that category. In feedback training, they are shown an exemplar, asked to assign it to a category, and then given feedback about the accuracy of their response. These two types of training were compared as observers learned two types of category structures--those in which optimal accuracy could be achieved via some explicit rule-based strategy, and those in which optimal accuracy required integrating information from separate perceptual dimensions at some predecisional stage. There was an overall advantage for feedback training over observational training, but most importantly, type of training interacted strongly with type of category structure. With rule-based structures, the effects of training type were small, but with information-integration structures, accuracy was substantially higher with feedback training, and people were less likely to use suboptimal rule-based strategies. The implications of these results for current theories of category learning are discussed.     

Hypoglycemia-induced suppression of luteinizing hormone (LH) secretion in intact female rhesus macaques: role of vasopressin and endogenous opioids

The first objective of this study was to determine whether insulin-induced hypoglycemia (IIH) inhibits LH secretion in unrestrained female macaques during the follicular phase of the menstrual cycle. There was a consistent inhibitory effect of hypoglycemia on LH secretion within 3 h in these females. This inhibition was likely an indirect effect since low glucose levels did not inhibit GnRH secretion from GT1-1 neurones in vitro. We next investigated whether administration of a vasopressin antagonist (AVPa) either alone, or with naloxone could reverse the IIH-induced inhibition of LH release. Females were studied in the follicular phase during 10 h periods with blood samples collected every 10 min. Experimental groups were IIH (n=6), IIH+AVPa (n=5) and IIH+AVPa+naloxone (n=4). The first 5 h of each study served as a control and hypoglycemia was then induced with insulin. The AVPa was given as a bolus (180 microg) just before the insulin and was followed by a continuous infusion (180 microg/h) for 5 h. Naloxone (5 mg/kg) was given with the AVPa and followed by a continuous infusion (5 mg/kg/h) for 5 h. In the IIH group, LH reached its lowest value 3-4 h after insulin. Neither AVPa nor AVPa+naloxone infusion reversed the inhibitory action of hypoglycemia on LH release. These data suggest that if there are inhibitory actions of vasopressin and endogenous opioids on GnRH release induced by hypoglycemia, they are not sufficient to explain the suppression of GnRH/LH release in intact female primates.     

PERSONALITY AND COGNITIVE ABILITY AS PREDICTORS OF JOB SEARCH AMONG EMPLOYED MANAGERS

Research on employee job search and separation traditionally focuses on situationally specific variables. Such variables may change with particular employment situations (e.g., job tenure, salary, perceived organizational success), they may be differentially relevant to work situations over time (e.g., education), or may reflect individual reactions to particular work situations (e.g., job satisfaction). More enduring individual characteristics, particularly personality and cognitive ability, may affect job search in consistent ways across different situations, but to date we have little empirical research on those effects. The present study extends traditional job search investigations by incorporating these two enduring individual characteristics–personality and cognitive ability. The value of these two enduring individual characteristics, in predicting job search, is then tested on a sample of U.S. executives. Cognitive ability as well as the personality dimensions of Agreeableness, Neuroticism, and Openness to Experience related positively to job search. These effects remained even in the presence of an array of situational factors previously shown to affect search. The relationship between Extroversion and job search became significant and positive in the presence of situational factors, particularly job satisfaction. Implications for future research and practice are discussed.