Bayesian methods applied to the generalized matching law.

We demonstrate the usefulness of Bayesian methods in developing, evaluating, and using psychological models in the experimental analysis of behavior. We do this through a case study, involving new experimental data that measure the response count and time allocation behavior in pigeons under concurrent random-ratio random-interval schedules of reinforcement. To analyze these data, we implement a series of behavioral models, based on the generalized matching law, as graphical models, and use computational methods to perform fully Bayesian inference.

Temporal discounting of aversive consequences in rats.

Previous research has extensively evaluated the impact of delay on the value of positive reinforcers, but the study of its impact on the value of aversive consequences is scarce. The present study employed a modification of Evenden and Ryan's procedure (1996, Psychopharmacology, 128(2), 161-170) to obtain data on temporal discounting of an aversive consequence, with rats as experimental subjects. In the first phase of the procedure, rats chose between one-pellet and four-pellet alternatives; when subjects developed preference for the larger-amount alternative, a shock was added to it, resulting in a loss of preference.

Rats behave optimally in a sunk cost task.

The sunk cost effect has been defined as the tendency to persist in an alternative once an investment of effort, time or money has been made, even if better options are available. The goal of this study was to investigate in rats the relationship between sunk cost and the information about when it is optimal to leave the situation, which was studied by Navarro and Fantino (2005) with pigeons. They developed a procedure in which different fixed-ratio schedules were randomly presented, with the richest one being more likely; subjects could persist in the trial until they obtained the reinforcer, or start a new trial in which the most favorable option would be available with a high probability.

Effect of streptozotocin-induced diabetes on performance on a progressive ratio schedule.

Rationale: It has been suggested that streptozotocin (STZ)-induced diabetes causes a motivational deficit in rodents. However, some of the evidence adduced in support of this suggestion may be interpreted in terms of a motor impairment rather than a motivational deficit.

Objective: This experiment examined the effect of STZ-induced diabetes on performance on a progressive ratio schedule.

Sensitivity to delay is affected by magnitude of reinforcement in rats.

Previous research has provided discrepant results about how reinforcement delay and magnitude are combined to determine the value of the alternatives in concurrent-chains schedules. In the present experiment, we analyzed a possible interaction between these characteristics of reinforcement, employing a two component concurrent-chains schedule, with rats as experimental subjects. Non-independent VI schedules were presented in the initial links of each component.

Evaluation of rate-dependency and internal clock effects of D-amphetamine.

The impact of two doses of d-amphetamine on rats' peak-interval performance was evaluated at two different points of training: with minimum training, 20 sessions, and with extended training, 120 sessions. At both points of training, none of the doses changed the location of the peak time; however, both doses caused a significant increase in the standard deviation of the response distribution during peak trials. Both results are incompatible with some previous empirical results, and with timing accounts that assume that dopamine modulates the pacemaker rate, but are compatible with a rate-dependent effect.

Learning to stop or reset the internal clock.

In the present experiments, after training rats in a standard fixed interval (FI) 30s schedule, we induced a change in the strategy employed during gap trials, by presenting during FI with gaps training, 9-s interruptions of the FI discriminative stimulus in 40% of the trials; in one type of interruption, after the discriminative stimulus resumed, the FI was re-started; in the second type of interruption, the FI had to be completed considering the time before the interruption. The effect of these manipulations was tested in a peak-interval with gaps procedure. The main result was that the strategy employed during gap trials depended on the type of interruption experienced during the training phase, both in a comparison between subjects (experiment 1) and within subjects (experiment 2).

Timing behavior in streptozotocin-induced diabetic rats.

There is evidence of deterioration of spatial cognition in streptozotocin (STZ)-induced diabetic rats. Here, we evaluate a possible dissociation in the cognitive deficits due to diabetes by examining another crucial aspect of animal cognition: temporal perception. Timing behavior and temporal memory were evaluated in STZ-induced diabetic rats employing two timing tasks: the peak-interval procedure, with its Gap variant, and the interval bisection task.

DRL performance of spontaneously hypertensive rats: dissociation of timing and inhibition of responses.

In this experiment, we used a differential reinforcement of low rates (DRL) schedule to evaluate the performance of spontaneously hypertensive rats (SHR), Wistar Kyoto (WKY) and Wistar (WIS) rats, with the goal of dissociating the processes of timing and inhibition of responses through the use of two quantitative models: the peak deviation analysis and the temporal regulation model. The subjects were divided in two groups; the first group was exposed to 70 sessions under a DRL 10s schedule. SHR rats showed an apparent temporary deficit in the inhibition of responses process; however, no differences among strains were observed in terms of the timing process.

Performance of spontaneously hypertensive rats in a peak-interval procedure with gaps.

The purpose of the present experiment was to evaluate timing behavior in spontaneously hypertensive rats (SHR), and compare it to the performance of Wistar Kyoto (WKY), and Wistar (WI) rats. In the first phase of the experiment, the subjects were exposed to a peak-interval procedure, in which fixed-interval 30s trials were alternated with nonreinforced and extended (peak) trials. After 60 sessions, an approximation to a Gaussian probability density function was fitted to the response rate during peak trials in order to estimate the peak time, the peak rate and the Weber fraction.

Interval bisection in spontaneously hypertensive rats.

An interval bisection procedure was used to study time discrimination in spontaneously hypertensive rats (SHR), which have been proposed as an animal model for the attention deficit hyperactivity disorder (ADHD); Wistar Kyoto and Wistar rats were used as comparison groups. In this procedure, after subjects learn to make one response (S) following a short duration stimulus, and another (L) following a long duration stimulus, stimuli of intermediate durations are presented, and the percentage of L is calculated for each duration. A logistic function is fitted to these data, and different parameters that describe the time discrimination process are obtained.

Energy budget versus temporal discounting as determinants of preference in risky choice.

Four pigeons and three ringneck doves responded on an operant simulation of natural foraging. After satisfying a schedule of reinforcement associated with search time, subjects could "accept" or "reject" another schedule of reinforcement associated with handling time. Two schedules of reinforcement were available, a variable interval, and a fixed interval with the same mean value.