An account of human “impulsivity” on self-control tasks

Three experiments examined the effects of economic constraint (time restriction—trials restriction) on adult humans' performance on concurrent chained schedules of reinforcement in which terminal links differed both in reward size and pre-reward delay levels. In the first, terminal links offered a long delay (20, 30, 40, 50 sec) followed by 2 points, or a short delay (10 sec) followed by 1 point. Initial links consisted of the same variable interval schedules for each alternative. Subjects showed a conditional sensitivity to increases in delay. Under a time constraint, there was an increasing preference for the smaller reward as the delay to the larger reward was increased, whereas under a trials constraint subjects were totally insensitive to such changes. In the second experiment, this finding was replicated using long and short periods of video game playing as large and small rewards. In the third experiment terminal link parameters remained constant (2 points after 15 sec, or 1 point immediately), but initial link parameters were manipulated (either VI 1-sec, 8-sec, or 20-sec) so that the higher relative rate of reward shifted from being associated with the small reward to being associated with the large reward. Again subjects chose differently under the two constraints. Subjects under the time constraint exhibited a preference for the small reward at all levels of initial link, but under the trials constraint subjects preferred the large reward. Subjects in the time constraint condition thus exhibited a maladaptive insensitivity to changes in the initial link duration. These findings are interpreted as supporting a miscalculation rather than a discounting interpretation of human performance on “self-control” tasks.     

Representative realism and absolute reality

This paper has benefitted from criticism by Allen Bäck. Of course, no one but myself is responsible for any of the ideas presented herein.     

Discrimination of five-dimensional stimuli by pigeons: Limitations of feature analysis

Pigeons were trained to discriminate between stimuli constructed using five orthogonal two-valued features. The stimuli consisted of stylized monochrome drawings of seeds. Two different training procedures (conditional and simultaneous discrimination) were used. In the first two experiments, the discrimination required was between polymorphous categories, in which a positive stimulus was defined as one in which three or more of the five features took their positive values. Discrimination in both experiments was imperfect; the pigeons' behaviour only came under the control of a subset of the available features (one to three in Experiment 1, three or four in Experiment 2). In Experiment 3, single features had to be discriminated, while the remaining features varied. It was found that all five features of the “seed” stimuli could be discriminated, but one of them was exceptionally difficult. The results show that pigeons do not reliably use all the features available to them when making category discriminations. This casts doubts on feature analysis as a basis for the excellent performance pigeons show when required to discriminate between categories of natural objects.     

Touch screen assays of behavioural flexibility and error characteristics in Eastern grey squirrels (<Emphasis Type="Italic">Sciurus carolinensis</Emphasis>)

Behavioural flexibility allows animals to adjust their behaviours according to changing environmental demands. Such flexibility is frequently assessed by the discrimination–reversal learning task. We examined grey squirrels’ behavioural flexibility, using a simultaneous colour discrimination–reversal learning task on a touch screen. Squirrels were trained to select their non-preferred colour in the discrimination phase, and their preferred colour was rewarded in a subsequent reversal phase. We used error rates to divide learning in each phase into three stages (perseveration, chance level and ‘learned’) and examined response inhibition and head-switching during each stage. We found consistent behavioural patterns were associated with each learning stage: in the perseveration stage, at the beginning of each training phase, squirrels showed comparable response latencies to correct and incorrect stimuli, along with a low level of head-switching. They quickly overcame perseveration, typically in one to three training blocks. In the chance-level stage, response latencies to both stimuli were low, but during initial discrimination squirrels showed more head-switches than in the previous stage. This suggests that squirrels were learning the current reward contingency by responding rapidly to a stimulus, but with increased attention to both stimuli. In the learned stage, response latencies to the correct stimulus and the number of head-switches were at their highest, whereas incorrect response latencies were at their lowest, and differed significantly from correct response latencies. These results suggest increased response inhibition and attention allowed the squirrels to minimise errors. They also suggest that errors in the ‘learned’ stage were related to impulsive emission of the pre-potent or previously learned responses.     

The impact of stress on mothers' memory of a natural disaster

The effects of stress on mothers' recall for a major hurricane were studied. Stress was objectively defined as low, moderate, or high according to the severity of home damage. This study of 96 mothers was conducted concurrently with L. E. Bahrick, J. F. Parker, R. Fivush, and M. Levitt (1998), allowing the authors to compare child and adult recall as a function of the same stressor. There was a quadratic relationship between storm severity and total recall for adults, similar to their children. Mothers' recall increased from low to moderate severity, but recall at moderate severity did not differ from high severity. These findings help clarify the effects of stress on the amount and type of information adults recall in retrospective accounts of naturalistic, temporally extended events.     

Middle childhood and adolescent contextual and personal predictors of adult educational and occupational outcomes: a mediational model in two countries

The authors examined the prediction of occupational attainment by age 40 from contextual and personal variables assessed during childhood and adolescence in 2 participant samples: (a) the Columbia County Longitudinal Study, a study of 856 third graders in a semirural county in New York State that began in 1960, and (b) the Jyv?skyl? Longitudinal Study of Personality and Social Development, a study of 369 eight-year-olds in Jyv?skyl?, Finland, that began in 1968. Both samples were followed up during adolescence and early and middle adulthood. Structural modeling analyses revealed that in both countries, for both genders, children's age 8 cognitive-academic functioning and their parents' occupational status had independent positive long-term effects on the children's adult occupational attainment, even after other childhood and adolescent personal variables were controlled for. Further, childhood and adolescent aggressive behavior negatively affected educational status in early adulthood, which in turn predicted lower occupational status in middle adulthood.     

Money as tool, money as drug: the biological psychology of a strong incentive

Why are people interested in money? Specifically, what could be the biological basis for the extraordinary incentive and reinforcing power of money, which seems to be unique to the human species? We identify two ways in which a commodity which is of no biological significance in itself can become a strong motivator. The first is if it is used as a tool, and by a metaphorical extension this is often applied to money: it is used instrumentally, in order to obtain biologically relevant incentives. Second, substances can be strong motivators because they imitate the action of natural incentives but do not produce the fitness gains for which those incentives are instinctively sought. The classic examples of this process are psychoactive drugs, but we argue that the drug concept can also be extended metaphorically to provide an account of money motivation. From a review of theoretical and empirical literature about money, we conclude that (i) there are a number of phenomena that cannot be accounted for by a pure Tool Theory of money motivation; (ii) supplementing Tool Theory with a Drug Theory enables the anomalous phenomena to be explained; and (iii) the human instincts that, according to a Drug Theory, money parasitizes include trading (derived from reciprocal altruism) and object play.     

Modeling the antecedents of proactive behavior at work

Using a sample of U.K. wire makers (N = 282), the authors tested a model in which personality and work environment antecedents affect proactive work behavior via cognitive-motivational mechanisms. Self-reported proactive work behaviors (proactive idea implementation and proactive problem solving) were validated against rater assessments for a subsample (n = 60) of wire makers. With the exception of supportive supervision, each antecedent was important, albeit through different processes. Proactive personality was significantly associated with proactive work behavior via role breadth self-efficacy and flexible role orientation, job autonomy was also linked to proactive behavior via these processes, as well as directly; and coworker trust was associated with proactive behavior via flexible role orientation. In further support of the model, the cognitive-motivational processes for proactive work behavior differed from those for the more passive outcome of generalized compliance.