David A. Eckerman

An experimental analysis of impulsivity and impulse control in humans

Abstract In choosing between small, immediate and large, delayed reward, an organism behaves impulsively if it chooses the small reward and shows impulse control if it chooses the large reward. Work with nonhumans suggests that impulsivity and impulse control may be derived from gradients of delayed reinforcement. A model developed by Ainslie and by Rachlin suggests that preference for the rewards should be a function of when the choice is made: small reward with no delay may be preferred to large reward with delay X, but adding delay T to both alternatives should shift preference to the large reward. Three experiments investigated this preference reversal in humans, using termination of 90 dba white noise as the reinforcing event. Experiment 1 showed that under some instructional conditions 90-sec noise off with no delay was preferred over 120-sec noise off after a 60-sec delay, but that preference shifted to the large reward when a 15-sec delay (T) was added to both alternatives. Experiment 2 replicated this preference reversal under two conditions of large, delayed reward, and with three rather than two values of T. Experiment 3 confirmed this effect of T and showed that some humans committed themselves to the large reward when commitment could be made some time before presentation of the reward alternatives. These data support the Ainslie-Rachlin model and extend it to human choice behavior.

Effects of scopolamine, pentobarbital, and amphetamine on radial arm maze performance in the rat ☆

Rats were trained to obtain food pellets from the end of each arm of an eight-arm radial maze. Baseline performance was characterized by very few entries into arms from which the food pellet had already been obtained. In Experiment 1, neither d-amphetamine (0.1-3.0 mg/kg) nor pentobarbital (1.0-10.0 mg/kg) affected choice accuracy, although the rate of arm-entry increased after d-amphetamine and decreased after pentobarbital. Scopolamine (0.1-1.0 mg/kg), on the other hand, reduced both accuracy and the rate of arm entry. In a second experiment, the effects of scopoalmine were replicated using a between-subjects design. Methylscopolamine (0.17, 1.0 mg/kg) was found to have little effect on performance. Multiple response criteria were also compared in the second experiment. Scopolamine was found to affect runs farther out the arm differently than it affected abbreviated arm entrances. A post-trial feeding test was also included to evaluate changes in reinforcer effectiveness, and showed that food continued to be a reinforcer after both scopolamine and methylscopolamine.

Development of the Behavioral Assessment and Research System (BARS) to detect and characterize neurotoxicity in humans

The Behavioral Assessment and Research System (BARS) is a computer-based testing system designed to assess neurobehavioral function in humans. It was developed to provide a series or battery of neurobehavioral tests optimized for the detection of neurotoxicity in non-mainstream human populations, specifically people with limited education or literacy. Key to meeting this goal were simply-stated instructions divided into an elemental series of steps, a 9BUTTON response unit to replace the computer keyboard for responding, and spoken instructions. Modifications all underwent serial testing in target populations to successively hone the changes to be more effective. A similar process was followed when developing adjustable parameters, test reliability assessments, and when implementing these tests with populations from different cultural groups and children. The principles and experiences that guided the development of BARS should inform the development of future testing systems to ensure that the new tests can be used with non-mainstream populations, which may be increasingly subject to neurotoxic exposures.

Enantioselective behavioral effects of threo-methylphenidate in rats

The relative potency of d- and l-threo-methylphenidate (d-MPH and l-MPH) was evaluated using three behavioral paradigms for rats: Responding maintained by a fixed-interval schedule of reinforcement (FI), responding maintained by a concurrent variable-interval schedule of reinforcement (Conc VI VI), and consumption of sweetened condensed milk during a 15-min free-access period. In each case the potency of the d-MPH enantiomer greatly exceeded that of the l-MPH enantiomer. Temporal control of responding was reduced (FI) choice responding was equalized for most rats (Conc VI VI), and milk consumption was suppressed by d-MPH and dl-MPH.

cTRAIN: A computer-aided training system developed in SuperCard for teaching skills using behavioral education principles

A computer-aided training program was developed in SuperCard and piloted with professional painters. Taking a modern programmed-instruction/behavioral-education approach, cTRAIN is structured as a series ofinformation sets. Each information set consists of a series of informationscreens (three to five recommended) followed by quiz screens (one to three recommended) structured as fourresponse multiple choice questions. Correct quiz responses produce positive feedback and continuation in the series, whereas incorrect responses result in “error“ feedback and return the student to the beginning of the information set to repeat the same information screens and the same quiz question. This report demonstrates a specific implementation, respiratory protection requirements, using the flexible cTRAIN system for developing training modules. Fifteen adults completed the respiratory protection program, demonstrating substantial and significant (p < .0001 by pairedt test) gains from baseline pretest (19.4 out of 30 questions) to the immediate posttest (28.1). Performance remained elevated (26.4) on a retest taken 1 week later.

Uncertainty Reduction and Conditioned Reinforcement

Pigeons were exposed to a single-key sequential choice procedure in which the choice phase was followed by either a multiple fixed-interval schedule of food reinforcement where different key-lights indicated which FI was in effect or by a mixed fixed-interval schedule of food reinforcement where the same key-light was present for either FI. In the choice phase a scrambled series of brief periods of blue and of green illumination of the key were presented. A single peck to blue produced the mult schedule; a single peck to green produced the mix schedule. The variable manipulated was the relative proportion of FI 10-sec. components in the mult and mix schedules. Pigeons pecked blue more frequently than green for proportions other than 0.00 and 1.00. Preference for blue was greater for the range of proportions from 0.03 to 0.50 than for the range from 0.50 to 0.97. Such asymmetry of preference is a problem for the information account of conditioned reinforcement.

Effects of methylphenidate and d-amphetamine on timing in the rat☆

Rats were trained to press a lever for food pellets provided according to a fixed interval 60-sec schedule of reinforcement. Probe trials (peak trials) assessed responding over two-min periods with no pellet delivered. The low rates of responding found early and late in probe trials were increased by methylphenidate and 1.0 mg/kg d-amphetamine (rate-dependent effect). Further, the mean time of responding (peak time) was shortened for both drugs (timing effect).

Interactive training versus reading to teach respiratory protection

A tenet of behavioral education is that interactive training produces superior retention compared with reading. However, this has not often been directly tested and never with practical occupational information in working adults. Adults from diverse occupational backgrounds learned the principles of proper respiratory protection presented (a) in a book, (b) on a computer monitor, (c) through interactive computerized training consisting of textual information and illustrative pictures followed by quizzes and feedback, or (d) passively viewing the information and quizzes in Condition c on a computer monitor. Interactive training produced significantly more correct test answers at immediate posttraining, 1 week, and 2 months. This study demonstrated the superiority of interactive training for teaching occupational safety and health information in working adults.

Neurobehavioral test strategies for environmental exposures in pediatric populations

The Agency for Toxic Substances and Disease Registry convened a workshop in Atlanta, GA, that evaluated approaches and methods to ascertain whether there are neurobehavioral sequelae to children and adults exposed to hazardous substances in the environment. This article, developed from that workshop, addresses the feasibility of employing extant neurobehavioral tests to screen pediatric populations. A matrix lists basic functions to be assessed during eight developmental periods ranging from birth to high school. The best of these neurobehavioral tests for pediatric populations and the types of assessment tools that are still needed are discussed. We make 10 specific recommendations to establish a hazardous substances neurobehavioral screen for pediatric populations, including appointing a review panel, developing a structured questionnaire, convening a conference on design and analysis, addressing minority and socially disadvantaged populations, coordinating adult and child assessment methods, information sharing among Federal agencies, baseline data, methodology research, research associated with hazardous worksites, and establishment of a pediatric databank.

Early-phase physiological response patterns to psychosexual stimuli: Comparison of male and female patterns

The onset and sequential changes of psychosexual arousal for male and female were compared. During an erotic film presentation, genital hemodynamic and groin skin temperature measures of sexual arousal recorded moderate to large increases for both sexes. A sequential analysis revealed strikingly similar male—female response patterns for both the genital and groin measures of arousal. Thus, the commonly held view that males typically show a greater sexual responsivity to visual erotic stimuli than do females was not supported.