The effects of combined perirhinal and postrhinal damage on complex discrimination tasks.

Rats with combined lesions of the perirhinal (PER) and postrhinal (POR) cortices were trained on a complex discrimination in the simultaneous feature-positive and feature-negative discrimination task. In this task, a panel light (L) paired with an auditory stimulus determined whether a tone (T) or white noise (N) would be rewarded (+) or not rewarded (-). Thus, the light feature determined whether the target auditory stimuli were rewarded or not. In each session, trial types were LT+, T-, N+, and LN-. We had hypothesized that damage to the target regions would impair performance on this task. Acquisition was altered in the lesioned rats, but not in the predicted direction. Instead, lesioned rats exhibited significantly enhanced acquisition of the discrimination. Manipulation of intertrial intervals indicated that reduction of proactive interference did not explain the enhancement. Lesioned rats were not different from controls on a multiple-cued interval timing task, providing evidence that the enhancement does not extend to all types of discriminations and is not due to a deficit in timing. Other research shows that rats with PER lesions are impaired on similar tasks, thus the enhancement is likely due to the effects of POR damage. Normally in this task, context is thought to accrue inhibitory control over other cues. Without this inhibitory control, animals might be expected to learn the task more efficiently. Our conclusion is that deficits in processing contextual information underlie the enhanced acquisition observed in rats with combined PER and POR damage on this complex discrimination task.

Stimulus control in multiple temporal discriminations.

In multiple fixed interval (FI) schedules, rats are trained to discriminate different FIs that are signaled by different stimuli. After extensive training, the different stimuli often acquire control over performance, observed by an earlier increase in responding for stimuli that signal shorter FIs, as compared with stimuli that signal longer FIs. The order in which the different FIs are trained, either intermixed across cycles or in blocks of several cycles, may seem irrelevant given that average performance at asymptote may be similar. In this study, rats were trained in two procedures with multiple FIs presented intermixed within sessions or in blocks of one interval per session. Similar performance was observed at asymptote, but an inspection of early cycles in each session revealed that different stimuli acquired control over performance only when trained intermixed within each session. Although the stimuli reliably signaled the upcoming FI, when trained in successive blocks of 60 cycles, rats rapidly adjusted performance early in the sessions on the basis of the temporal aspects of the task, and not on the basis of the stimulus presented in the current cycle. These results are discussed in terms of overshadowing of the stimuli by temporal cues and in terms of conditions under which a stimulus acquires control over performance.

Correction to: Rules of Conduct for Behavior Analysts in the Presence of Hypothetical Constructs: A Commentary on Eckard and Lattal (2020).

[This corrects the article DOI: 10.1007/s40614-020-00272-w.].

Rules of Conduct for Behavior Analysts in the Presence of Hypothetical Constructs: A Commentary on Eckard and Lattal (2020).

Eckard and Lattal (2020) summarized the behavioristic view of hypothetical constructs and theories, and then, in a novel and timely manner, applied this view to a critique of internal clock models of temporal control. In our three-part commentary, we aim to contribute to the authors' discussion by first expanding upon their view of the positive contributions afforded by constructs and theories. We then refine and question their view of the perils of reifying constructs and assigning them causal properties. Finally, we suggest to behavior analysts four rules of conduct for dealing with mediational theories: tolerate constructs proposed with sufficient reason; consider them seriously, both empirically and conceptually; develop alternative, behavior-analytic models with overlapping empirical domains; and contrast the various models. Through variation and selection, behavioral science will evolve.

A comparison of empirical and theoretical explanations of temporal discrimination.

The empirical goals were to describe the behavior of rats trained on multiple temporal discriminations and to use these descriptions to predict behavior observed under new training conditions. The theoretical goals were to fit a quantitative theory to behavior from one training condition, estimate parameters for the intervening perception, memory, and decision processes, and use these parameters to predict behavior observed under new conditions. Twenty-four rats were trained on a multiple-peak-interval procedure with two stimuli that were presented individually (Stimulus A and B), or in compound (Compound AB); either different responses (Experiment 1) or the same response (Experiment 2) were reinforced during the presentations of Stimulus A, Stimulus B, and Compound AB. The patterns of correct and stimulus-error responses during Stimulus A and Stimulus B (Experiment 1) were used as elements that, with summation rules, predicted behavior under new conditions (Compound AB, Experiment 1; Stimulus A, Stimulus B, and Compound AB, Experiment 2). A comparison of the success of the empirical and theoretical goals supported the use of a quantitative theory of behavior to explain the data.

A modular theory of learning and performance.

We describe a theory to account for the acquisition and extinction of response rate (conditioning) and pattern (timing). This modular theory is a development of packet theory (Kirkpatrick, 2002; Kirkpatrick & Church, 2003) that adds a distinction between pattern and strength memories, as well as contributing closed-form equations. We describe the theory using equations related to a flow diagram and illustrate it by an application to an experiment with repeated acquisitions and extinctions of a multiple-cued-interval procedure using rats. The parameter estimates for the theory were based on a calibration sample from the data, and the predictions for different measures of performance on a validation sample from the same data (cross-validation). The theory's predictions were similar to predictions based on the reliability of the behavior.

Differences between simultaneous and blocked training detected by a transfer test.

Secondary data analysis was used to compare responding early on a transfer test from rats previously trained simultaneously or successively on multiple temporal discriminations for the same number of trials [Guilhardi, P., Church, R.M., 2005 a. Dynamics of temporal discrimination. Learn. Behav., 33, 399-416]. Three fixed intervals (30, 60, and 120 s) were signaled by three stimuli (light, noise, and clicker). Twelve rats were trained with the three stimulus-interval pairs intermixed on each experimental session (simultaneous condition); 12 other rats were trained in successive blocks of 10 sessions on each pair (blocked condition). Then, all rats had a transfer test in which all three stimulus-interval pairs were presented intermixed on each session. Rats in the simultaneous and blocked condition responded similarly during training, but differently during early stages of the transfer test. One possibility is that rats in the blocked condition were controlled by the previous interval, not by the current stimulus. These results challenge the usual assumptions from models of timing and conditioning that both simultaneous and blocked training produce learning of the associations between stimulus and interval in a multiple interval training task.

Shifts in the psychophysical function in rats.

The primary goal was to compare results from a free-operant procedure with pigeons [Machado, A., Guilhardi, P., 2000. Shifts in the psychometric function and their implications for models of timing. J. Exp. Anal. Behav. 74, 25-54, Experiment 2] with new results obtained with rats. The secondary goal was to compare the results of both experiments with dependent variables that were not used in the original publication. As in the original study with pigeons, rats were trained on a two-alternative free-operant psychophysical procedure in which left lever press responses were reinforced during the first and second quarters of a 60-s trial, and right lever press responses were reinforced during the third and fourth quarters of the trial. The quarters were reinforced according to four independent variable interval (VI) schedules of reinforcement. The VI duration was manipulated in each quarter, and shifts in the psychophysical functions that relate response rate with time since trial onset were measured. The results obtained with rats were consistent with those previously obtained with pigeons. In addition, results not originally reported were also consistent between rats and pigeons, and provided insights into the perception, memory, and decision processes in Scalar Expectancy Theory and Learning-to-Time Theory.

Learner Preference Between Massed- and Alternating-Trial Sequencing when Teaching Stimulus Relations to Children with Autism.

Two children with autism were assessed for preference between intersession distribution of mastered and unknown instructional trials on a computerized matching-to-sample task consisting of 12 total learning opportunities. Choice responses yielded presentation of either massed-trial sequencing (six unknown/six mastered stimuli relations or vice-versa) or alternating-trial sequencing delivery (alternation of unknown and mastered stimuli relations) followed by reinforcement for correct responses. An extinction condition served as an experimental control. Both children demonstrated a preference for the alternating-trial sequencing condition, and implications for instructional programming and possible effects to delays to higher rates of reinforcement are discussed.

Effects of repeated acquisitions and extinctions on response rate and pattern.

The procedure developed by R. A. Rescorla (2002) was used to study the effects of repeated acquisitions and extinctions of head entry responses into a food cup by rats. In each of 4 20-session phases, food was delivered at the end of particular 30-s auditory and visual stimuli, but not at the end of different 30-s auditory and visual stimuli. Based on response rates to individual stimuli and compound stimuli, the increase in response rate in acquisition occurred more rapidly than the decrease in extinction. Acquisition, but not extinction, occurred faster after successive transitions between acquisition and extinction. Temporal gradients of responding developed during acquisition and remained during extinction. Conclusions based on mean response rate, temporal gradients, and transfer tests were consistent.

A Turing test of a timing theory.

A quantitative theory of timing or conditioning can be evaluated with a Turing test in which the behavioral results of an experiment can be compared with the predicted results from the theory. An example is described based upon an experiment in which 12 rats were trained on three fixed-interval schedules of reinforcement, and a simulation of the predicted results from a packet theory of timing. An objective classification rule was used to determine whether a sample from the data or a sample from the theory was more similar to another sample from the theory. With an ideal theory, the expected probability of a correct classification would be 0.5. The observed probability of a correct classification was 0.6, which was slightly, but reliably, greater than 0.5. A Turing test provides a graded metric for the evaluation of a quantitative theory.

How rats combine temporal cues.

The procedures for classical and operant conditioning, and for many timing procedures, involve the delivery of reinforcers that may be related to the time of previous reinforcers and responses, and to the time of onsets and terminations of stimuli. The behavior resulting from such procedures can be described as bouts of responding that occur in some pattern at some rate. A packet theory of timing and conditioning is described that accounts for such behavior under a wide range of procedures. Applications include the food searching by rats in Skinner boxes under conditions of fixed and random reinforcement, brief and sustained stimuli, and several response-food contingencies. The approach is used to describe how multiple cues from reinforcers and stimuli combine to determine the rate and pattern of response bouts.

The lack of behavioral effects of fenbendazole: a medication for pinworm infection.

Pinworm infection in rodent laboratories is common and often treated with fenbendazole, which is effective and has a low toxicity level. However, very little is known about the behavioral effects of the drug. The purpose of this study was to determine the behavioral effects of fenbendazole on rats tested by using various conditioning and timing procedures. These behavioral effects were examined both between animals (i.e., control versus medicated treatments) and within animals (baseline-treatment-baseline design). Fenbendazole reduced the detection of pinworm eggs, and it had no significant behavioral effects across multiple levels of analysis (e.g., from overall response rates to response patterns to interresponse intervals). All behavioral differences (e.g., discrimination ratios) were a result of task variables. These results suggest that behavioral studies are unlikely to be influenced by fenbendazole treatment given before or during a study.

Social validation of the New England Center For Children--Core Skills Assessment.

We investigated the social validity of the NECC Core Skills Assessment (NECC-CSA) with parents and professionals as participants. The NECC-CSA is a measurement tool consisting of direct and indirect measures of skills important to all individuals with autism, across the lifespan. Participants (N = 245) were provided with a list of 66 skills, 47 of which were Core Skills from the NECC-CSA, and were asked to indicate which items they considered to be foundational. Participants endorsed items from the NECC-CSA as foundational skills, more than they endorsed the other items. Differences between parents and professionals are described and detailed with respect to individual assessment items. The NECC-CSA consists of socially validated skills that can be taken as a starting point for programs of instruction for individuals with ASDs.

The effect of stimulus discriminability on strategies for learning multiple temporal discriminations.

The goal was to identify training conditions under which temporal intervals that are signaled by different stimuli are memorized (i.e., the temporal behavior is readily shown to be under stimulus control). Undergraduate students were trained on three signaled temporal discriminations using a peak procedure. The intervals were trained in either blocks of trials or with trials intermixed within the session, and then they were given a transfer test with intermixed trials. There were two levels of stimulus discriminability, defined by the similarity of the stimuli. Most participants memorized the intervals when the discriminations were intermixed within the session, or were easy, but not when the discriminations occurred in blocks and were difficult. In the transfer tests, those participants trained in the difficult discrimination that occurred in blocks of trials typically continued to perform as they did during the last-trained interval, regardless of the stimulus presented. These results are better explained by a memory retrieval than a memory storage account.

The generality of empirical and theoretical explanations of behavior.

For theoretical explanations of data, parameter values estimated from a single dependent measure from one procedure are used to predict alternative dependent measures from many procedures. Theoretical explanations were compared to empirical explanations of data in which known functions and principles were used to fit only selected dependent measures. The comparison focused on the ability of theoretical and empirical explanations to generalize across samples of the data, across dependent measures of behavior, and across different procedures. Rat and human data from fixed-interval and peak procedures, in which principles (e.g., scalar timing) are well known, were described and fit by a theory with independent modules for perception, memory, and decision. The theoretical approach consisted of fitting closed-form equations of the theory to response rate gradients calculated from the data, simulating responses using parameter values previously estimated, and comparing theoretical predictions with dependent measures not used to estimate parameters. Although the empirical and theoretical explanations provided similar fits to the response rate gradients that generalized across samples and had the same number of parameters, only the theoretical explanation generalized across procedures and dependent measures.

The pattern of responding after extensive extinction.

Extensive extinction greatly reduces response rate and increases the relative frequency of short interresponse times, but does not affect temporal learning or operant response rate. In each of two experiments, 24 rats were trained in a multiple cued interval procedure with three stimuli (noise, light, and clicker) at three intervals (30, 60, and 120 sec). In Experiment 1, after 50 sessions of extinction, response rate decreased from about 25 to 0.5 responses/min, but temporal discriminations were maintained and the initial response gradients in reacquisition had a pattern that corresponded with the original (rather than current) training conditions. In Experiment 2, these results were replicated and extended by examination of the effect of stimulus duration on response patterns during extinction, but its lack of effect on reacquisition. The similarity of the initial performance in reacquisition to the asymptotic performance in acquisition was presumably due to the similarity of context. The individual subject data may be downloaded from www.psychonomic.org/archive.

Dynamics of temporal discrimination.

The purpose of this research was to describe and explain the acquisition of temporal discriminations, transitions from one temporal interval to another, and asymptotic performance of stimulus and temporal discriminations. Rats were trained on a multiple cued interval (MCI) procedure with a head entry response on three signaled fixed-interval schedules of reinforcement (30, 60, and 120 sec). They readily learned the three temporal discriminations, whether they were presented simultaneously or successively, and they rapidly adjusted their performance to new intervals when the intermediate interval was varied daily. Although exponential functions provided good descriptions of many measures of temporal discrimination, different parameter values were required for each measure. The addition of a linear operator to a packet theory of timing with a single set of parameters provided a quantitative process model that fit many measures of the dynamics of temporal discrimination.

Measures of temporal discrimination in fixed-interval performance: a case study in archiving data.

The primary data of many experimental studies of animal learning and performance consist of the times at which stimuli and reinforcers were delivered, and the times at which responses occurred. The articles based on most of these studies report selected data, either from some sessions or some animals, or summary measures of the animals' behavior. The primary data are sufficient to produce any of the selected and summary measures, but the selected and summarized data cannot produce many of the measures used in other experimental reports. It is now feasible to archive the primary data from animal behavior experiments so that they are accessible for others to perform secondary analysis. The value of such secondary analysis of archived data is described with a case study in which rats were trained on three fixed-interval schedules of reinforcement. The full data set may be downloaded from www.psychonomic.org/archive/.