Beyond drug effects and dependent variables: the use of the Poisson-Erlang model to assess the effects of D-amphetamine on information processing

Several studies have shown that d-amphetamine (DAMP) speeds mean reaction time (RT). However, the use of mean RT may obscure important aspects of the drug response. Therefore we applied the Poisson-Erlang (PE) stochastic model of choice reaction time proposed by Pieters (1985) to the RT distribution. This model proposes that the RT distribution is generated by two states: Processing (P) and Distraction (D). RT represents the sum of the time spent in each of these states. P is the time taken to complete a set of cognitive operations which are required to give a correct response. D represents the time taken by all other activities. RTs were collected using a task (SERS) in which stimulus and response complexity each had two levels, easy and hard. Subjects were tested pre- and postdrug. Drug conditions were: placebo, 10 mg d-amphetamine (DAMP), 4 mg of the dopamine agonist, pimozide, and a combination of DAMP and pimozide (COMBO). Parameters of the model were derived using methods described by Pieters. Four measures were analyzed: Processing Time (PT); Mean Time per distraction (XTD); Distraction Rate (DR); and Total Distraction Time per trial (TDT). Mean RT is also presented. Analyses of the effects of task conditions on the parameters of the model were made using the predrug sessions. Mean RT was increased by both stimulus and response complexities as was PT. TDT was increased by the task conditions. The PE measures did not change over days. DAMP speeded mean RT. However, this effect did not interact with the task factors. DAMP speeded processing and reduced distraction. Processing was speeded only in the hard response condition, distraction time was reduced only in the easy response condition. The results indicate that the PE model can be successfully applied to fast RT tasks. More importantly, the parameters of the model revealed important pharmacological effects that were not apparent in mean RT. DAMP speeds cognitive operations related to motor preparation and reduces the effects of distraction. Consistent with past studies there are no indications that DAMP interacted with stimulus processing. The distraction effect appears to be mediated by an increase in the rate of distraction and a decrease in the average time of these distractions.     

Behavioral contrast and response independent reinforcement

Four pigeons received pre-training that included presentation of the reinforcer independently of behavior and then baseline training on a variable-interval schedule of reinforcement. With the introduction of a multiple schedule, in which the first stimulus was associated with a response contingent and a second stimulus with a response independent, 1-min variable-interval schedule, a reduction in response rate was obtained in the second component, which was not accompanied by a behavioral contrast effect in the first component. A further three pigeons were given the same pre-training and baseline training before the introduction of an otherwise identical multiple schedule, in which no reinforcement occured in the second component. Behavioral contrast was obtained from all three subjects. The results indicated that under conditions of constant reinforcement density a reduction in responding is not a sufficient condition for the occurrence of behavioral contrast.     

Book reviews

Patterns of Redundancy: A Psychological Study. By A.C. Staniland. London: Cambridge university Press. 1966. Pp. viii + 216. 45s. $50.

Signal Detection theory and Psychophysics. By David M. Green and John A. Swets. London and New York: Wiley. 1966. Pp. xi + 455. 104s.

Acquisition of Skill. Edited by E.A. Bilodeau. New York and London: Academic Press. 1966. Pp. xiii + 539. £5.0

Readings in Verbal Learning: Contemporary Theory and Research. Edited by Donald H. Kausler. London and New york: Wiley. 1966. Pp. xii + 578. 60s.

Experiments in Visual Perception. Edited by M.D. Vernon. London: Penguin Modern Psychology. Pp. 430. 8s 6d.

Motivation. Edited by Dalbir Bindra and Jane Stewart. London: Penguin Modern Psychology. 1966. Pp. 352. 8s. 6d.

Pattern Recognition: Theory, Experiment, Computer Simulations, and Dynamic Models of Form Perception and discovery. Edited by Loenard Uhr. New York and London: wiley. 1966. Pp. xii + 393. 68s. cloth, 45s. paper.

Advances in the Study of Behavior. Volume I. Edited by D. S. Lehrman, R. A. Hinde and E. shaw. New York and London: Academic Press. 1965. Pp. x + 320. 76s.

Fields of Psychology. Edited by J. P. Guilford. Third Edition. Princeton, N. J. and London: Van Nostrand. 1966. Pp. x + 350. 72s.

Attitudes. Edited by M. Jahoda and N. Warren. London: Penguin Modern Psychology. 1966. Pp.375. 8s. 6d.

Personality Assessment. Edited by Boris Semeonoff. London: penguin Modern Psychology. 1966. Pp. 443. 8s. 6d

The Psychology Of Learning. By R. Borger and A. E. M. Seaborne. Harmondsworth. Middx.: penguin Books (Pelican Orginal). 1966. Pp. 243. 5s.

Eliminating the Unconscious: A Behaviourist View Psycho-analysis. By T.R. Miles. Oxford and London: Pergamon. 1966. Pp. xviii + 171. 17s. 6d.

Manuel Pratique de Psychologie Experimentale. By Paul Fraisse. Paris: Presses universitaires de France. 2nd edition, 1963. Pp. 392. 20F.

Abstraction and Concept Formation. By Anatol pikas. London: Oxford University press (Harvard University Press). 1966. Pp.xiii + 303. 56s.

Tactics of Scientific research. By Murray Sidman. London and New York: Basic Books. 1966. Pp. x + 428. $17s. 6d.

Psychodynamics and Hypnosis: New Contributions to the practice and theory Of hypno-therapy. Compiled and Edited by Milton V. Kline. Springfield. Illinois: Thomas. 1966. Pp. xi + 194. $8.75.

Psychology: The Science of Mental Life. By G.A Miller. London: Penguin Books. 1966. Pp. 415.7s. 6d.

The Memory System of the Brain. By J. Z. Young. London: Oxford University Press. 1967. Pp. vii + 128. 28s.     

Exploratory behaviour in elevated and enclosed mazes

Rats given daily exploratory trials in a simple enclosed maze showed a decline in activity from day to day, while animals exploring an elevated maze showed no decline between days. In a further experiment exploration of either an elevated or an enclosed maze was found to cease after about 15 min. The implications of these findings are discussed.     

Retroactive raising of a sensory threshold by a contralateral stimulus

In an experiment designed to extend Howarth and Treisman's recent observations on the lowering of the visual and auditory threshold produced by a warning stimulus, it has been found that the threshold to electrical stimulation of one forearm is raised by a similar stimulus on the other forearm. As in the earlier experiments the “warning” was effective if it came 100 millisec. before or after the threshold stimulus. The effect increased with increasing warning strength over the range of five near-threshold strengths used.

These results appear to be inconsistent with the explanation previously proposed to account for the retroactive lowering of threshold. This suggested that the warning was acting simply as a marker, reducing the subject's uncertainty as to when the stimulus was coming. The fact that the rise in threshold was also induced retroactively shows that some interaction must be occurring in the central processes concerned in perception, and that it cannot be explained in terms of attenuation of the afferent volley.     

Familial Aggregation of ADHD Characteristics

Patterns of familial aggregation of ADHD symptoms in parents of ADHD and non-ADHD children were examined. Within the ADHD sample, symptom aggregation was examined as a function of biological relationship, parent and child gender, and children's comorbid diagnoses. Participants consisted of parents of 579 children with ADHD, Combined Type participating in the multimodal treatment study of children with ADHD and parents of 288 normal control participants. Adult symptoms of ADHD were measured by both self-report and report of a significant other. Results indicated that the parents of children with ADHD had higher ratings of inattention/cognitive problems, hyperactivity/restlessness, impulsivity/emotional lability, and lower self-concept than parents of children without ADHD on both self-report and other-report ratings. Within the ADHD sample of children, other-report ratings of inattention/cognitive problems and impulsivity/emotional lability were higher for biological parents compared to nonbiological parents whereas self-ratings were not related to biological status. These findings support previous research documenting familial aggregation of ADHD and appear to strengthen the hypothesis that there is a genetic contribution to ADHD.     

Who Wants to Learn Forever? Hyperbole and Difficulty with Lifelong Learning

This paper addresses the issue of how lifelonglearning, globalisation and capitalism arerelated within late modernity. It is criticalof the argument that there is now anincreasingly homogenous global economy that isknowledge based and that unambiguously requiresa high level of cognitive skills in itsworkers. The idea that globalisation producessuch rapid changes in the world of work thatlearning must be ongoing to cope with it ischallenged.It is argued that the key issue forpolicy-makers concerned to encourage lifelonglearning is funding the provision of thoselearning opportunities that would otherwise notbe available. People can learn many worthwhilethings at work, at home and elsewhere ininformal associations. It makes little sense toduplicate the opportunity to learn those thingsformally or even in many cases, formally todistinguish such learning from living andworking.     

The validity of psychomotor vigilance tasks of less than 10-minute duration.

The 10-min psychomotor vigilance task (PVT) has often been used to assess the impact of sleep loss on performance. Due to time constraints, however, regular testing may not be practical in field studies. The aim of the present study was to examine the suitability of tests shorter than 10 min. in duration. Changes in performance across a night of sustained wakefulness were compared during a standard 10-min PVT, the first 5 min of the PVT, and the first 2 min of the PVT. Four performance metrics were assessed: (1) mean reaction time (RT), (2) fastest 10% of RT, (3) lapse percentage, and (4) slowest 10% of RT. Performance during the 10-min PVT significantly deteriorated with increasing wakefulness for all metrics. Performance during the first 5 min and the first 2 min of the PVT deteriorated in a manner similar to that observed for the whole 10-min task, with all metrics except lapse percentage displaying significant impairment across the night. However, the shorter the task sampling time, the less sensitive the test is to sleepiness. Nevertheless, the 5-min PVT may provide a viable alternative to the 10-min PVT for some performance metrics.