Differences in rats and pigeons suboptimal choice may depend on where those stimuli are in their behavior system

Failure to find a distance effect in pigeon choice: Manipulating amount and delay of reinforcement

The choice behavior of primates, including humans, displays a distance effect: Latency to choose between alternatives appears to increase with smaller differences in value. There is, so far, no demonstration of this effect in birds. Tests of distance effects in birds have been conducted in binary choice situations with a dominant alternative, where one alternative is superior to the other in all aspects that meaningfully contribute to value (e.g., provides access to the same reinforcer, but with a shorter delay). The present study considers the possibility that including dominant alternatives in choice tests precludes distance effects. Four pigeons were presented with binary choices between alternatives that varied in amount and delay. Some choices had a dominant alternative (smaller-sooner or larger-later vs. smaller-later) and some did not (smaller-sooner vs. larger-later). Across phases, only the delay to the smaller-sooner reinforcer varied. Distance effects were expected to be expressed as longer latencies as choice between smaller-sooner and larger-later reinforcers approached indifference. Despite the sensitivity of choice to differences in amount and delay, no distance effect was observed. Alternative explanations for the failure to find a distance effect in pigeon choice, including the Sequential Choice Model (SCM), are discussed.

The essential value of the alternatives of the suboptimal choice procedure is different for pigeons and rats

Suboptimal choice is the preference for a discriminative alternative with low probability of reinforcement, over a non-discriminative alternative with higher probability of reinforcement. Pigeons consistently prefer the discriminative alternative, whereas rats prefer the non-discriminative; the variables accounting for this difference are not yet clear. The economic concepts related to demand curves have been used to calculate the essential value of different types of reinforcers, so they may be useful to compare the value of the alternatives in the suboptimal choice procedure. The goal of this study was to calculate the essential value of each of the alternatives presented in the suboptimal choice procedure to assess if pigeons (Experiment 1) and rats (Experiment 2) value them differently. In both experiments, the fixed ratio requirement in the initial link was increased throughout sessions in order to obtain the demand curve and calculate the essential value by fitting the exponential-demand model. A Bayesian Linear Mixed-Effects Model indicated that pigeons had higher essential values for the discriminative alternative, whereas rats obtained higher essential values for the non-discriminative alternative. These results suggest that preferences in the suboptimal choice procedure are indeed based on the essential value of the alternatives, and provide a new paradigm to study the variables affecting this phenomenon.

Suboptimal choice by pigeons is eliminated when key-pecking behavior is replaced by treadle-pressing

In the study of suboptimal choice, a reliable result is that pigeons strongly prefer an alternative that signals whether a reinforcer will be delivered or not over another alternative without that information even if the first provides a lower probability of reinforcement. In the aforementioned research, key pecking has been the operant response and illuminated keys the discriminative stimuli. In the present study we modified both of these aspects of the procedure in order to analyze the generality of suboptimal preferences of pigeons and to investigate the effect of changes in the incentive salience of the discriminative stimuli. To accomplish this, we presented pigeons a choice situation with the same parameters of reinforcement than previous research, but with treadle pressing as the choice response and ambient lights as discriminative stimuli. Under these conditions, most of the pigeons showed optimal behavior and a high degree of discrimination of the stimuli associated with the discriminative alternative. A control condition with key pecking as choice response and keylights as discriminative stimuli showed that the same pigeons turned to be suboptimal, a result that discards the possibility that the optimality found in the main condition was a consequence of a particular characteristic of our sample of subjects or of our procedure. We discuss the influence that the attribution of incentive salience to the discriminative stimuli has on suboptimal choice in both pigeons and rats.

Information preferences across species: Pigeons, rats, and dogs

We tested the information preferences of three different species; pigeons, rats and dogs. Eight animals of each species received forced trials that produced one of two stimulus sequences. In the first sequence, response to an initial stimulus led to one of two other stimuli, one of which guaranteed a food reward was coming and the other of which guaranteed no food reward was coming. In the second sequence, response to an initial stimulus led to one of two other stimuli, both of which predicted food reward on 50 % of the trials. The net reinforcement rate for both of the sequences was 50 %. On probe test trials, both initial stimuli were presented, and the subject chose between the informative and the non-informative cue, and the percent choice of the information sequence, in which stimuli predicted food or no food reliably, was recorded for each species across 10 sessions. Statistical tests showed that although pigeons showed a preference for the information sequence, neither rats nor dogs showed this preference. Experimental and ecological explanations are discussed.

Challenges and Opportunities in Animal Models of Gambling-like Behavior

In the past several years, there has been an explosion of interest in animal models of risk-based decision-making, a fundamental process associated with gambling disorder. While early work focused on establishing various tasks for assaying decision-making, current studies are determining the (subtle and not-so-subtle) influence of cues in driving risky decisions to better understand problem gambling. In addition, these decision-making paradigms are now being used to investigate comorbid conditions such as substance dependence or brain injury and replicating observations from human patients. These animal models have now developed to a point where therapeutic interventions may be assessed for not just gambling disorder, but also a number of other conditions which engender risky decision-making.

Six clarifications for behaviour systems

The precursors of contemporary behaviour systems theory were hotly debated, and yet a similar critical fervour has not followed the second generation of behaviour systems research. I raise six items of potential or extant misunderstanding concerning behaviour systems perspectives, and attempt to set straight some of the assumptions and what motivated them, with attention to historical and theoretical context. The six challenges in focus are: 1) variety of conceptualisation of consummation; 2) potential misapprehensions about the role of general search; 3) ambiguity of predictions concerning response form; 4) ambiguity concerning what aspects are modelled as hierarchical; 5) assumptions of directedness; and 6) the relevance of spontaneous activity. For each of these six issues, some clarification is offered.

Rats' optimal choice behavior in a gambling-like task

Among the different procedures that model gambling behavior in non-human animals, the "suboptimal choice procedure" has been extensively employed for analyzing the impact of environmental cues on choice behavior. It has been repeatedly demonstrated that pigeons prefer an alternative that infrequently presents a stimulus that signals a larger amount of reinforcement, than another alternative that always presents a stimulus associated with a smaller amount of reinforcement, even though the net rate of reinforcement is lower in the former. In the present study, we tested rats in the magnitude version of the suboptimal choice procedure. Eight rats were given a choice between two alternatives: a) one in which a stimulus predicting the delivery of ten pellets was presented with probability (p) = 0.2 and a stimulus predicting zero pellets was presented with p = 0.8, and b) one in which either of two stimuli predicted the delivery of three pellets with p = 1.0. Contrary to the consistent and robust suboptimal behavior of pigeons, rats preferred the optimal alternative. This effect occurred despite the high index of discrimination of the stimuli associated with the different outcomes shown by the rats. The relevance of this result to the development of animal models of gambling behavior is discussed.