A Pathological View of Disease

This paper is a response to Christopher Boorse's recent defense of hisBiostatistical Theory (BST) of health and disease. Boorse maintains that hisconcept of theoretical health and disease reflects the ``consideredusage of pathologists.' I argue that pathologists do not use ``disease' inthe purely theoretical way that is required by the BST. Pathology does notdraw a sharp distinction between theoretical and practical aspects ofmedicine. Pathology does not even need a theoretical concept of disease. Itsfocus is not theoretical, but practical; pathology's goal is to contribute tothe healing of patients. Pathology, even experimental pathology, is notvalue-free. Not only ``disease' but also such terms as ``nerve' and ``organ'are laden with conceptual values.     

An evaluation of a brief multiple-stimulus preference assessment with adolescents with emotional-behavioral disorders in an educational setting

Brief multiple-stimulus-without-replacement (MSWO) preference assessments were conducted with 3 adolescent boys with emotional-behavioral disorders in the context of their public school educational program. The reinforcing effects of stimuli identified as high, medium, and low preference were then evaluated using an alternating treatments design in which, following an initial baseline, stimuli were delivered contingent on on-task behavior. High-preference stimuli produced the highest percentages of on-task behavior for all 3 participants.     

Use of a lag differential reinforcement contingency to increase varied selections of classroom activities

The present study evaluated the effects of a lag differential reinforcement contingency on 2 students' activity selections using reversal designs. Results showed that the lag contingency was responsible for promoting increased novel selections, engagement in diverse activities, and greater progress with respect to programmed academic activities.     

The role of the response-reinforcer relation in delay-of-reinforcement effects

The role of the response-reinforcer relation in maintaining operant behavior under conditions of delayed reinforcement was investigated by using a two-operandum (i.e., two-key) procedure with pigeons. Responding on one key was reinforced under a tandem variable-interval differential-reinforcement-of-other-behavior (tandem VI DRO) schedule. The schedule defined a resetting unsignaled delay-of-reinforcement procedure in that a response was required when the interfood interval of the VI schedule lapsed, but further responding during the DRO component on either key reset the time interval. This ensured a fixed delay duration between any response and reinforcement. Responding on another key, physically identical to the first one except for spatial location, otherwise was without consequence. The location of the key correlated with the delay-of-reinforcement procedure varied between sessions according to a semirandom sequence. Differences in response rates between the two keys were greater, with proportionally higher rates on the key correlated with the delay-of-reinforcement procedure, the longer the delay-of-reinforcement procedure remained correlated with the same key. Differences in responding on the two keys also increased within individual sessions. These results suggest that the response-reinforcer relation is the primary determinant of responding when responding is acquired and maintained with delayed reinforcement.     

SAVING THE BEST FOR LAST? A CROSS-SPECIES ANALYSIS OF CHOICES BETWEEN REINFORCER SEQUENCES

Two experiments were conducted to compare choices between sequences of reinforcers in pigeon (Experiment 1) and human (Experiment 2) subjects, using functionally analogous procedures. The subjects made pairwise choices among 3 sequence types, all of which provided the same overall reinforcerment rate, but differed in their temporal patterning. Token reinforcement schedules were used in both experiments and the type of exchange schedule varied across blocks of sessions. Some conditions permitted immediate exchange of tokens for consumable reinforcers (food for pigeons, video access for humans); in other conditions, tokens accumulated and were exchanged for consumable reinforcers only at the end of the sequence. Choice patterns in the immediate-exchange conditions were generally similar across species, with both pigeons and humans preferring sequences with the shortest delay to the initial reinforcer in the series. The results are broadly consistent with models of temporal discounting expanded to include the impact of sequences of delayed reinforcers acting in parallel from the time of the choice. Preferences were less consistent with discounting models in the delayed exchange conditions. Questionnaire data gathered at the end of the experiment were consistent with prior results of questionnaire studies, but showed no straightforward relation to the observed choice patterns, urging caution in the extrapolation of results from one decision-making domain to the other.     

Effects of time between trials on rats' and pigeons' choices with probabilistic delayed reinforcers

Parallel experiments with rats and pigeons examined reasons for previous findings that in choices with probabilistic delayed reinforcers, rats' choices were affected by the time between trials whereas pigeons' choices were not. In both experiments, the animals chose between a standard alternative and an adjusting alternative. A choice of the standard alternative led to a short delay (1 s or 3 s), and then food might or might not be delivered. If food was not delivered, there was an "interlink interval," and then the animal was forced to continue to select the standard alternative until food was delivered. A choice of the adjusting alternative always led to food after a delay that was systematically increased and decreased over trials to estimate an indifference point--a delay at which the two alternatives were chosen about equally often. Under these conditions, the indifference points for both rats and pigeons increased as the interlink interval increased from 0 s to 20 s, indicating decreased preference for the probabilistic reinforcer with longer time between trials. The indifference points from both rats and pigeons were well described by the hyperbolic-decay model. In the last phase of each experiment, the animals were not forced to continue selecting the standard alternative if food was not delivered. Under these conditions, rats' choices were affected by the time between trials whereas pigeons' choices were not, replicating results of previous studies. The differences between the behavior of rats and pigeons appears to be the result of procedural details, not a fundamental difference in how these two species make choices with probabilistic delayed reinforcers.     

Transitional and steady-state choice behavior under an adjusting-delay schedule

Twelve rats made repeated choices on an adjusting-delay schedule between a smaller reinforcer (A) that was delivered immediately after a response and a larger reinforcer (B) that was delivered after a delay which increased or decreased by 20% depending on the subject's choices in successive blocks of trials. In two phases of the experiment (100 sessions and 40 sessions), reinforcer sizes were selected which enabled theoretical parameters expressing the rate of delay discounting and sensitivity to reinforcer size to be estimated from the ratio of the indifference delays obtained in the two phases. Indifference delays, calculated from adjusting delays in the last 10 sessions of each phase, were shorter when the sizes of A and B were 14 and 25 μl of a 0.6 M sucrose solution than when they were 25 and 100 μl of the same solution. The ratio of the indifference delays was significantly smaller than that predicted on the basis of an assumed linear relation between reinforcer size and instantaneous reinforcer value, consistent with a previous proposal that this relation may be hyperbolic in form. Estimates of the rate of delay discounting based on the ratio of the two indifference delays (mean, 0.08 s(-1)) were similar to values obtained previously using different intertemporal choice protocols. Estimates of the size-sensitivity parameter (mean 113 μl) were similar to estimates recently derived from performance on progressive-ratio schedules. In both phases of the experiment, adjusting delays in successive blocks of trials were analyzed using the Fourier transform. The power spectrum obtained from individual rats had a dominant frequency that corresponded to a period of oscillation of the adjusting delay between 30 and 100 trial blocks (mean, 78). Power in the dominant frequency band was highest in the early sessions of the first phase and declined with extended training. It is suggested that this experimental protocol may have utility in neurobehavioral studies of intertemporal choice.     

Eating pathology in female gymnasts: Potential risk and protective factors

Although participation in sports that emphasize aestheticism, such as women's gymnastics, are associated with higher rates of eating pathology, little is known about the risk and protective factors involved in this process. We established and tested a model proposing that body surveillance and body shame are processes by which pubertal development and training may uniquely contribute to pathological eating by sampling 100 competitive female gymnasts via questionnaires. We further tested whether self-esteem moderated several model relationships. Results demonstrated that pubertal development was associated with higher levels of body surveillance, body shame and disordered eating; whereas greater time spent training was associated with lower levels of body shame and disordered eating. Finally higher self-esteem was associated with lower levels of disordered eating, less body surveillance, and less body shame. Potential risk and protective factors for the development of eating pathology in female gymnasts are discussed.     

Response acquisition by zebrafish (Danio rerio) with delayed reinforcement

Zebrafish (Danio rerio) is a common vertebrate animal model in biomedical research and is a promising species for studying how genes interact with environmental factors in determining behavior. The present study investigated how reinforcement parameters affect zebrafish behavior by assessing response acquisition with delayed reinforcement, which has been studied with other species (e.g., rats, pigeons, humans, etc.) but not with zebrafish. Twenty‐four experimentally naïve subjects were exposed to a tandem fixed‐ratio 1 differential‐reinforcement‐of‐other‐behavior x‐s schedule of reinforcement, where x varied across subjects. There were six different delay‐to‐reinforcement durations and sets of four fish were assigned to each delay duration. All of the fish assigned to a 0‐, 0.5‐, or 1‐s delay acquired responding. Two fish acquired responding with a 3‐s delay and one fish appeared to have acquired it with a 6‐s delay although the latter result was less clear. None acquired responding with a 12‐s delay. These results suggest that zebrafish behavior is sensitive to delays to reinforcement and the time frame over which reinforcement is effective may be limited approximately to 6 s. This time frame is shorter than that found with other species. Practical and theoretical implications of the present finding are discussed.