Dynamic response-by-response models of matching behavior in rhesus monkeys

We studied the choice behavior of 2 monkeys in a discrete-trial task with reinforcement contingencies similar to those Herrnstein (1961) used when he described the matching law. In each session, the monkeys experienced blocks of discrete trials at different relative-reinforcer frequencies or magnitudes with unsignalled transitions between the blocks. Steady-state data following adjustment to each transition were well characterized by the generalized matching law; response ratios undermatched reinforcer frequency ratios but matched reinforcer magnitude ratios. We modelled response-by-response behavior with linear models that used past reinforcers as well as past choices to predict the monkeys' choices on each trial. We found that more recently obtained reinforcers more strongly influenced choice behavior. Perhaps surprisingly, we also found that the monkeys' actions were influenced by the pattern of their own past choices. It was necessary to incorporate both past reinforcers and past choices in order to accurately capture steady-state behavior as well as the fluctuations during block transitions and the response-by-response patterns of behavior. Our results suggest that simple reinforcement learning models must account for the effects of past choices to accurately characterize behavior in this task, and that models with these properties provide a conceptual tool for studying how both past reinforcers and past choices are integrated by the neural systems that generate behavior.     

Pre-frontal executive committee for perception,working memory,attention, long-term memory,motor control,and thinking: a tutorial review

As an explicit organizing metaphor, memory aid, and conceptual framework, the prefrontal cortex may be viewed as a five-member 'Executive Committee,' as the prefrontal-control extensions of five sub-and-posterior-cortical systems: (1) the 'Perceiver' (dominant-right-hemisphere ventral-lateral prefrontal cortex--VL/PERC-PFC) is the frontal extension of the ventral perceptual stream (the VL/PERC system) which represents the world and self in object coordinates; (2) the 'Verbalizer' (dominant-left-hemisphere ventral-lateral prefrontal cortex system--VL/VERB-PFC) is the frontal extension of the language stream (the VL/VERB system) which represents the world and self in language coordinates; (3) the 'Motivator' (ventral/medial-orbital pre-frontal cortex--VMO-PFC) is the frontal cortical extension of a subcortical extended-amygdala stream (the VMO system) which represents the world and self in motivational/emotional coordinates; (4) the 'Attender' (dorsal-medial/anterior cingulate--DM/AC-PFC) is the frontal cortical extension of a subcortical extended-hippocampal stream (the DM/AC system) which represents the world and self in spatiotemporal coordinates and directs attention to internal and external events; and (5) the 'Coordinator' (the dorsolateral prefrontal cortex--DL-PFC) is the frontal extension of the dorsal perceptual stream (the DL system) which represents the world and self in body- and eye-coordinates and controls willed action and working memory. This tutorial review examines the interacting roles of these five systems in perception, working memory, attention, long-term memory, motor control, and thinking.     

Generative Concern, Political Commitment, and Charitable Actions

The implications of psychosocial generativity (Erikson, 1950) for understanding contemporary politics were explored. Study 1 replicated, in two samples, previous findings that generativity concerns are related to a variety of political activities, including the expenditure of time and money in support of political organizations. Using path analyses, Study 2 extended these findings and demonstrated how midlife generativity concerns interacted with political orientation and interest in politics to produce stronger relationships with giving. These findings suggest that people view the political arena as one important way to improve society and thereby manifest cultural generativity. Although focusing on the domain of politics, these studies highlight the complexity of generativity as a construct; broad concerns with generativity operate within the context of ideological commitments to produce greater levels of generative activity.     

Assessment Centre Observation Procedures: An Experimental Comparison of Traditional,Checklist and Coding Methods

Concern about the construct validity of assessment centre judgements has led to calls for research into observers’ cognitive processes. In an experiment comparing the Traditional observation procedure against use of a Behavioural Checklist and of Behavioural Coding, six outcome variables were examined. The methods were found to yield similar outcomes in terms of accuracy of judgement, accuracy of written evidence, correlation between dimension ratings, and attitude toward the method employed. However, significant between-method differences were observed in variability between observers and in their willingness to recommend a procedure. It is argued that Behavioural Coding has special merit in assessment centres; the method reduces the cognitive demands placed on assessors, and valuably structures their information-processing. Traditional objections to simultaneous observation and classification are shown to be inappropriate.     

Alcohol problems and relapse: Can the clinic combat the community?

Despite over a decade of research and debate into the issue of relapse the majority of people in treatment for alcohol-related problems still relapse. In this paper the results of an innovative relapse prevention and management programme are reported. It was found that a cognitive-behavioural package of strategies reduced the likelihood of relapse. On average, clients receiving this experimental package took four times longer to return to any alcohol use and seven times longer to return to ‘heavy drinking’ than did a conventional treatment control group. However, notwithstanding these results, 60 per cent of the experimental group did return to harmful drinking. The authors question whether further refinement of these procedures is possible, and suggest that if relapse rates are to be further reduced then greater attention needs to be given by counsellors to clients' social environment.     

Aggressive disposition,alcohol, and aggression

This study investigated the effect of aggressive disposition on intoxicated and non-intoxicated aggressive behavior. Prior aggressiveness was measured with a structured questionnaire. Based on a bipartite split of scores, 28 subjects were assigned to the high aggressor group, and 29 to the low aggressor group. Subjects in both disposition groups were then randomly assigned to either a drunk or sober condition, and participated in a competitive reaction time task involving the administering and receiving of electric shocks to/from a fictitious opponent under conditions of high and low provocation. Aggression was defined as shock level intensity delivered to the sham opponent. When highly provoked, sober high aggressors were significantly more aggressive than low aggressors, thus validating the measure of aggressive disposition. When intoxicated, highly provoked individuals in both the high and low aggressive disposition groups attained equal levels of aggression. It was low aggressors who responded to escalated provocation with a significant increase in aggression responding when intoxicated. These results lend support to the notion that a pharmacological effect of alcohol can increase aggressive behaviour. Aggr. Behav. 23:11–18, 1997. © 1997 Wiley-Liss, Inc.     

Correlates of suicidal behaviors among Asian American outpatient youths

Medical record abstraction was conducted at an ethnic-specific mental health outpatient clinic to identify correlates of suicidal behaviors in a sample of 285 Asian American youths. Some risk factors, such as parent-child conflict and age, which have been associated with suicidality in majority group youths, predicted suicidality in this sample, whereas other risk factors, such as gender, did not generalize to this sample. Acculturation interacted with the risk factor of parent-child conflict to predict suicidality. Less acculturated Asian youths were at proportionally greater risk for suicidality under conditions of high parent-child conflict than were their more acculturated counterparts. This finding underscores the importance of culture as a context for determining the relevance of stressors for potentiating psychopathology.