Concurrent variation of response bias and sensitivity in an operant-psychophysical test

The yes-no signal detection procedure was applied to a single-response operant paradigm in which rats discriminated between a standard auditory intensity and attenuated comparison values. The payoff matrix was symmetrical (with reinforcing brain stimulation for correct detections and brief time-out for errors), but signal probability and intensity differences were varied to generate a family of isobias and isosensitivity functions. The d’ parameter remained fairly constant across a wide range of bias levels. Isobias functions deviated from a strict matching strategy as discrimination difficulty increased, although an orderly relation was maintained between signal probability value and the degree and direction of response bias.     

Choice behavior and the accessibility of the reinforcer

In Experiment 1, matching of relative response rates to relative rates of reinforcement was obtained in concurrent variable-interval schedules when the absolute values of the two concurrent variable-interval schedules varied from 6 sec and 12 sec to 600 sec and 1200 sec. Increases in the duration of the changeover delay, however, produced decreases in the relative response rates and, consequently, some deviation from matching. In Experiment 2, matching of relative response rates to the relative duration of the reinforcer failed to occur when the equal variable-interval schedules arranging access to the two different reinforcer durations (1.5 and 6 sec) were varied in size from concurrent variable-interval 10-sec schedules to concurrent variable-interval 600-sec schedules.     

Positive interaction (induction) in multiple variable-interval, differential-reinforcement-of-high-rate schedules

The effect of increases in the rate of responding in one component of a multiple schedule upon the rate of responding in a second component was investigated. Pigeons were exposed to a multiple schedule where both components were initially variable-interval schedules having the same parameter value. After rate of key pecking stabilized, one component was changed to a schedule that differentially reinforced high rates of responding. Rate of reinforcement in this varied component was adjusted to remain equal to rate of reinforcement in the constant (variable-interval) component. Four of five pigeons showed a maintained increase in rate of responding during both the constant and varied components, even though rates of reinforcement did not change.     

The influence of eye movements and eye position on perception of the visual vertical

Summary Four experiments are reported which involved the adjustment of two points of light in an otherwise dark room to the visual vertical. In the first two experiments different point separations (corresponding to visual angles of about 2° and 23°) were employed in an attempt to control the degree of scanning eye movements. Binocular adjustments to the visual vertical during body tilt were influenced by the point separation (Exp. 1), but monocular adjustments with the head upright were not (Exp. 2). Using the larger point separation and fixating the top point the visual vertical using the right eye was counterclockwise of that with fixation of the bottom point when the head was upright (Exp. 3), but this difference was not found for judgments during tilt (Exp. 4). The results were discussed in terms of the rotational changes in eye position accompanying scanning eye movements and ocular elevation and depression.

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Zusammenfassung Es wird über vier Experimente berichtet, in denen es um die Einstellungen zweier Lichtpunkte in eine vertikale Richtung geht. In den ersten zwei Experimenten sollte der Einfluß der Fixierbewegungen der Augen geprüft werden. Der Winkelabstand der Lichtpunkte betrug 2° oder 23°. Bei seitwärts geneigtem Körper und binokularer Betrachtung wurde ein Unterschied gefunden (Exp. 1). Bei aufrecht gehaltenem Kopf und monokularer Betrachtung dagegen zeigte sich kein Unterschied (Exp. 2). Wurde in aufrechter Körperlage und bei einem Punktabstand von 23° der obere Punkt mit dem rechten Auge fixiert, so verschob sich die scheinbare Vertikale im Uhrzeigersinn; sie verschob sich noch weiter im Uhrzeigersinn, wenn der untere Punkt fixiert wurde (Exp. 3). Bei geneigtem Körper wurde dagegen kein Unterschied festgestellt (Exp. 4). Die Ergebnisse werden im Zusammenhang mit der Augendrehung diskutiert, die mit dem scanning sowie mit der Auf- und Abbewegung der Augen beim Fixieren verbunden ist.

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This research was carried out while I was a recipient of a Forschungsstipendium from the Alexander von Humboldt-Stiftung, appreciation for which is gratefully acknowledged. I also wish to thank the subjects who participated in the experiments.     

A comparison of five methods of illusion measurement

The relative efficiency of five techniques of illusion measurement were tested on parametric variations of the Mueller-Lyer and Ebbinghaus figures. The methods of average error, reproduction, and selection from a graded series all showed significant effects of configurational variations. The subjective scaling techniques each failed to measure adequately changes in illusion magnitude for one illusion configuration. The suitability of the tested measures for group administration is also discussed.     

The capacity for rapid shifts in level of mental concentration

This investigation continues the exploration of a largely neglected topic in the field of attention, levels of mental concentration, by ascertaining under optimal conditions the capacity for shifting quickly from one level to another. Previous research in our laboratory had applied a set of five post-hypnotically cued levels of concentration or “cognitive arousal”, covering a very wide range, to a variety of perceptual and cognitive tasks. In the present study two highly trained undergraduate hypnotic subjects, one male and one female, were given progressively shorter time durations in which to respond to the post-hypnotic cues before viewing tachisto-scopically flashed consonants under cue influence. The results indicate a striking capacity to shift degrees of cognitive arousal very rapidly to one extreme or the other, on the order of 100 ms or less.     

Rehearsal strategy as a function of recall expectation

The subjects were divided into three groups with respect to their expectations concerning a recall task given after the final trial of the usual STM distractor procedure. Group 1 were told only that they would have to recall during each trial's recall interval, thus did not expect to have to recall again. Group 2 were told that they would have to recall all the words presented in the experiment at the end of the last trial, in addition to the trial-by-trial recall. Group 3 were told only that they would have to recall after all words had been presented and they sat passively through the presentation trials. In addition to their recall expectations, half of the subjects in each group received a 2-s presentation and half received a 5-s presentation interval. It was found that the length of the presentation interval had an effect on the number of words recalled at the end of all trials, but recall expectancy did not. However, expectancy did determine the rehearsal strategies of subjects and hence the serial positions from which items were recalled.