The microanalysis of fixed-interval responding

The fixed-interval schedule of reinforcement is one of the more widely studied schedules in the experimental analysis of behavior and is also a common baseline for behavior pharmacology. Despite many intensive studies, the controlling variables and the pattern of behavior engendered are not well understood. The present study examined the microstructure and superstructure of the behavior engendered by a fixed-interval 5- and a fixed-interval 15-minute schedule of food reinforcement in the pigeon. Analysis of performance typical of fixed-interval responding indicated that the scalloped pattern does not result from smooth acceleration in responding, but, rather, from renewed pausing early in the interval. Individual interresponse-time (IRT) analyses provided no evidence of acceleration. There was a strong indication of alternation in shorter-longer IRTs, but these shorter-longer IRTs did not occur at random, reflecting instead a sequential dependency in successive IRTs. Furthermore, early in the interval there was a high relative frequency of short IRTs. Such a pattern of early pauses and short IRTs does not suggest behavior typical of reinforced responding as exemplified by the pattern found near the end of the interval. Thus, behavior from clearly scalloped performance can be classified into three states: postreinforcement pause, interim behavior, and terminal behavior.     

Analgesic and opioid involvement in the shock-elicited activity and escape deficits produced by inescapable shock

Three experiments examined the involvement of analgesic processes and endogenous opioids in the production of the shuttlebox escape acquisition and unconditioned activity deficits which follow exposure to inescapable shock. Experiment 1 found that the opiate antagonist naltrexone administered before the inescapable shock session interfered with the shuttlebox escape acquisition deficit which would normally follow. Experiment 2 found naltrexone to completely prevent the unconditioned activity deficit. The final experiment revealed that dexamethasone, a synthetic glucocorticoid which abolishes the analgesia produced by inescapable shock, reversed the activity deficit. These results indicate that endogenous opioids may be involved in the production of both the escape acquisition and activity deficits. They also suggest that the analgesia produced by these opioids may participate in the mediation of the activity deficit, even though analgesia is not involved in producing the shuttlebox acquisition deficit.     

Discrimination and generalization by rats of temporal stimuli lasting for minutes

In three experiments, rats learned to respond differentially to reinforced and nonreinforced trials when the length of the intertrial interval (ITI) predicted the trial outcome (reinforcement or nonreinforcement). Rats in control groups, for whom the length of the ITI did not predict the outcome, did not show differential performance on nonreinforced and reinforced trials. Generalization gradients obtained following discrimination training were comparable to those obtained following discrimination training with other types of discriminative stimuli. That is, groups which had shown differential performance in discrimination training yielded generalization gradients with fastest speeds at the previously reinforced ITIs, slowest speeds at the previously nonreinforced ITIs, and intermediate speeds at ITIs of intermediate length. Control groups yielded flat gradients across all ITIs tested. These effects were shown for relative time discrimination (short time = reinforcement, long time = nonreinforcement, or the reverse) and also for an absolute time discrimination (long and short time = reinforcement, middle time = nonreinforcement or the reverse). This method was effective for time duration measured in minutes rather than seconds, as is more commonly the case.     

Concurrent schedules: Spatial separation of response alternatives

Four pigeons were exposed to independent concurrent variable-interval 20-second variable-interval 60-second schedules of reinforcement. A transparent partition was inserted midway between the two response keys. The length of the partition was systematically manipulated. Increasing partition length produced a decrease in changeover rate in Experiment 1. Over-matching was observed with a partition length of 20 centimeters. In Experiment 2 a four-second limited hold was added to the schedules. Increasing partition length produced a decrease in changeover rate that exceeded the decrease observed in Experiment 1. This manipulation produced nearly exclusive choice of the variable-interval 20-second component. The present results, together with results obtained in related research, suggest that deviation from matching is a function of procedural variables that determine the consequences of a changeover response.     

Accommodation fatigue and dark focus: The effects of accommodation-free visual work as assessed by two psychophysical methods

Past studies of accommodation fatigue have yielded inconsistent results, partly because they have not used direct measures of accommodation, and partly because they may have been based on a misleading conception of the nature of accommodation. The dual-innervation theory of accommodation suggests that the resting position of accommodation may be neuromuscular rather than just muscular, and that it lies not at optical infinity, as assumed by older conceptions, but at some intermediate position (dark focus). Among the predictions that may be deduced from this theory is that long-term visual work not requiring active accommodation will not induce fatigue. The present study involved continuous measurements of dark focus for 10 young adults over a 3-h period, using the laser optometer with two psychophysical procedures Ibracketing and staircase. Consistent with the prediction, no changes in dark focus were found, in spite of the demanding visual task. Furthermore, it was found that both psychophysical methods yielded essentially identical results. The practical and theoretical implications of these results are discussed, and recommendations are given regarding situations in which each of the psychophysical methods is likely to be most useful.     

Changes in excitability in motor cortex (representation of foreleg) of the dog depending on signal signification of flexor reaction during elaboration of trans switching

Excitability in a cortical representation of a foreleg was determined during elaboration of transswitching in dogs in three variations depending upon the stimulus used as a Conditioned stimulus (CS). If the flexor reaction to direct stimulation of the motor cortex was used as a CS, excitability changes of opposite signs appeared in the cortical representation of the foreleg, the threshold of flexion decreased in the alimentary situation and increased in the defense situation. Such changes in excitability were observed during instrumental conditioned transswitching. If subthreshold stimulation of the motor cortex was used as the CS, the threshold of flexion increased in both situations in approximately equal degree.     

Choice reaction time with a random foreperiod

Choice reaction latencies were measured at three different a priori probabilities for two stimulus alternatives. Unlike the results of some other studies, the mean latency of a given response was nearly the same whether the response was correct or incorrect. The discriminable stimuli were a 1000- or a 1700-Hz tone presented at 70 dB SPL. Latencies and standard deviations, based on about 17,000 observations, are reported for three observers. The data are compared with predictions of the optimum sequential model of Wald and Stone and two modifications of that random-walk model, one proposed by Link and Heath and the other proposed by Laming. Fast-guess analyses were also carried out. The three-parameter version of either the sequential or the modified random-walk models provided reasonably accurate predictions of the mean data for each observer. The parameters estimated by the fast-guess analysis were unrealistic. There are three obvious differences between this experiment and most previous choice reaction-time experiments. First is stimulus modality#x2014;we used an auditory signal, whereas most of the previous studies used a visual signal. Second, the observers practiced more in this experiment than in most previous experiments. Finally, there was a random foreperiod with a heavy penalty for anticipations. One or more of these factors is the probable reason for the discrepancy between our results and those of previous studies.     

An Apple II package for computer-assisted telephone interviewing

This paper describes an Apple II (an Apple-compatible) microcomputer package for a computer-assisted telephone interviewing (CATI) system. This system generates random telephone numbers within any number of exchanges that the user supplies, automatically dials the telephone, prompts the interviewer with each question, and records and permanently saves each response. It also provides a printed copy of the collected data by frequency of response in each question category. The Apple II CATI package is readily available, inexpensive, and easy to program in the BASIC language.     

The use of color for the secondary elaboration of the dream

Freud's term sekund?re Bearbeitung has been translated as both "secondary revision" and "secondary elaboration." In keeping with a distinction made by Silber (1973), the term secondary elaboration is used in this paper to indicate the process by which further dream modification occurs after dream recall in order to deepen the disguise of the manifest content for the analyst. Clinical cases are presented in an attempt to demonstrate the sole use of color for the alteration of dreams subsequent to their initial recall. Secondary elaboration in these cases is attributed to resistance to transference. Further, the clinical material indicates that the secondary elaboration simultaneously serves a communicative function.