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.     

Changing the response unit from a single peck to a fixed number of pecks in fixed-interval schedules

Each of three pigeons was studied first under a standard fixed-interval schedule. With the fixed interval held constant, the schedule was changed to a second-order schedule in which the response unit was the behavior on a small fixed-ratio schedule (first a fixed-ratio 10 and then a fixed-ratio 20 schedule). That is, every completion of the fixed-ratio schedule produced a 0.7-sec darkening of the key and reset the response count to zero for the next ratio. The first fixed-ratio completed after the fixed-interval schedule elapsed produced the 0.7-sec blackout followed immediately by food. These manipulations were carried out under two different fixed-interval durations for each bird ranging from 3 min to 12 min. The standard fixed-interval schedules produced the typical pause after reinforcement followed by responding at a moderate rate until the next reinforcement. The second-order schedules also engendered a pause after reinforcement, but responding occurred in bursts separated by brief pauses after each blackout. For a particular fixed-interval duration, post-reinforcement pauses increased slightly as the number of pecks in the response unit increased despite large differences in the rate and pattern of key pecking. Post-reinforcement pause increased with the fixed-interval duration under all response units. These data confirm that the allocation of time between pausing and responding is relatively independent of the rate and topography of responding after the pause.     

Schedule control of the vocal behavior of Cebus monkeys

The vocal behavior of three Cebus monkeys was maintained by fixed-ratio schedules of response dependent reinforcement at values between fixed-ratio 1 and fixed-ratio 15. In one monkey that was exposed to variable-interval, fixed-interval, and conjunctive fixed-ratio fixed-interval schedules of reinforcement, vocal responding occurred at a low rate, but schedule-appropriate patterns were maintained. The rates and patterns of responding engendered indicated that the vocal operant can be brought under schedule control in the monkey by the use of response-dependent reinforcement.     

Lick-shock contingencies in the rat

Hungry rats were allowed to lick an 8% sucrose solution and then one of four lick-shock contingency conditions was superimposed on the licking baseline. These conditions were: free-operant avoidance, free shock, punishment, and no shock. From highest to lowest response rates, the groups fell in the order-avoidance, no shock, free shock, and punishment. Lick rates adjusted rapidly to introduction and removal of the contingencies. Post-shock responding was lowest in the punishment condition and highest in the free shock condition. No method was found simultaneously to equate shock frequency and separate response rates for the three shock contingency conditions. Only small, or no, reductions in shock rate occurred over sessions under the free-operant avoidance schedule when the shock-shock interval was 10 sec but large reductions occurred when the shock-shock interval was reduced to either 1 or 2 sec.     

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.     

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.     

Pause measures during reading and recall in serial list learning

An investigation is reported into pausing and grouping during the serial learning of letter strings, when presented randomly by length and when presented in ascending order. Mean pause times for the reading and recall of longer lists were significantly greater than for lists of shorter span due to extended pausing at specific list positions. In general, reading rhythms were duplicated during recall. Subjects were highly consistent in maintaining their level of pause duration across lists and responded to additions in list length by increasing their number of groups, not by increasing group size. Triadic sequences were the most popular form of spontaneous organization. Pausing measures are discussed as indices of organizational strategies.