Aversive properties of the negative stimulus in a successive discrimination

Experiment I sought to determine if the stimulus correlated with extinction in a successive discrimination was an aversive stimulus. An escape response provided an index of aversive control. Two groups of pigeons were exposed to a multiple variable-interval 30-sec extinction schedule. For the experimental group, a single peck on a second key produced a timeout during which all lights in the chamber were dark. For the control group, pecks on the second key had no contingency. The rate of responding on the timeout key during extinction for the experimental group was higher than that of the control group during all sessions of discrimination training except the first. In Exp. II, green was correlated with variable interval 30-sec and red was correlated with variable-interval 5-min. Timeouts were obtained from variable-interval 5-min. There were more timeouts from extinction in Exp. I than from variable-interval 5-min in Exp. II. Experiment III showed that not presenting the positive stimulus reduced the number of timeouts from the negative stimulus for the two birds from Exp. I that had the highest rate of timeouts from extinction, but had little effect on the two birds that had the lowest rate of timeouts. These results suggest that in a multiple schedule, the stimulus correlated with extinction, or the lower response rate, functions as a conditioned aversive stimulus. Explanations of the timeout response in terms of extinction produced variability, displaced aggression, and stimulus change, were considered but found inadequate.     

Some effects of fixed-interval duration on response rate in a two-component chain schedule

In Exp. I three pigeons were trained on a two-component chain schedule. Responding on a 1-min variable-interval schedule in the initial component led to a sequence of two fixed-interval schedules in the terminal component. The rate of reinforcement in the terminal component was kept constant while the values of the two fixed intervals were varied. Three combinations of fixed-interval schedules were studied, FI 0.25, FI 1.75 (minutes) or FI 1.00, FI 1.00, or FI 1.75, FI 0.25. The rate for each subject declined in the initial component as the value of the first fixed interval was increased. Experiment II was conducted to assess the role of the second fixed-interval schedule in the terminal component in determining the rate of responding in the initial component. For each chain schedule the rate of responding in the initial component was determined both with and without the second of the sequence of fixed intervals. In all three cases the rate of responding in the initial component decreased when the second fixed interval was removed. Increasing the first fixed interval in Exp. I had a greater effect on variable-interval performance than did the removal of the second fixed interval in Exp. II.     

Intra-Limb Specificity of Motor Response Consistency

Two separate experiment using motor responses evaluated the specificity vs. generality of response consistency when the various tasks used the same limb for response. In Exp. I four similar tasks requiring rapid right arm movement were defined and, in Exp. II, Ss had to “hit” a moving target with either a maximal or moderately fast right hand movement. Although the mean intercorrelations among tasks were generally moderate to low (mean r = .85 and .30, respectively for Exp. I and II) the intercorrelations using response consistency scores (the SD of S’s responses about his own mean) were lower for Exp. I (mean r = .54) and similar for Exp. II (mean r = .30). These findings provided little support for a notion of a general within-limb factor of motor response consistency.     

Some effects of response independent reinforcers in multiple schedules

In Exp. I, rats' lever presses were conditioned on multiple variable-interval variable-interval schedules. Changing one of the multiple schedule components to variable time reduced responding in that component. Further reductions in responding occurred in both components when the schedule was changed to multiple variable-time variable-time. After reinstating the multiple variable-interval variable-time schedule, lower response rates were maintained in the variable-time component during a series of stimulus reversals. In Exp. II, replacement of extinction components of multiple variable-interval extinction or multiple extinction extinction with variable-time schedules for single sessions (probe) resulted in response rate increments in those components. In the former schedule these increases were concomitant with response decreases during the variable-interval components. Response increases in the variable-time probes were related to conditioning history and, as a result, to response probability at the time of the probe.     

Some determinants of inhibitory stimulus control

Interspersed reinforcement and extinction during discrimination learning generate a U-shaped gradient of inhibition about the stimulus correlated with extinction. The present work showed that extinction is not a necessary determinant of inhibitory stimulus control. In Exp. I, a reduction in the rate of reinforcement, through a shift from a multiple variable-interval 1-min variable-interval 1-min schedule to a multiple variable-interval 1-min variable-interval 5-min schedule, resulted in a post-discrimination line orientation gradient of inhibition about the stimulus correlated with the variable-interval 5-min schedule. In Exp. II, the rates of reinforcement, correlated with a pair of stimuli, were held constant during a shift from a multiple variable-interval 1-min variable-interval 1-min schedule to a multiple variable-interval 1-min differential-reinforcement-of-low-rate schedule. Inhibitory stimulus control about the stimulus correlated with the differential reinforcement of low rate was obtained. In both experiments, a reduction in the rate of responding during one stimulus and behavioral contrast during the other stimulus preceded the observation of inhibitory stimulus control.     

Effects of target-background luminance ratios upon the autokinetic illusion

This study investigated effects of the target-background luminance ratios upon the autokinetic illusion, with special emphasis on manipulation of the background intensity. Exp. 1, in which the effects of four levels of target luminance were examined against the completely dark background, showed that the target luminance did not affect the illusion as long as the target was small enough in size (0.17 degrees in visual angle). This result confirmed the suggestion by Edwards in 1954. In Exp. II effects of the target-background luminance ratios were examined by varying the luminance of target and background independently. Dominant illusory patterns at the luminance ratio 1 were "pendulum-like" and "bobbing"; these differed from those at higher ratios ("winding"). On the other hand, latency and duration were not affected by the ratios. These findings suggest that the movement pattern is effective in specifying the autokinetic illusion, if it is appropriately categorized and represented.     

Wavelength generalization and preference in monochromatically reared ducklings

Two experiments determined the effects of early color experience on gradients of wavelength generalization. In each experiment, one group of ducklings was raised in monochromatic (589 nanometers) sodium-vapor light and a second group, in white light. In Exp. I, ducklings pecked a key transilluminated by 589 nanometers. In a subsequent test, the group raised in white light produced steeper gradients. However, several monochromatically reared ducklings produced gradients as steep as those for the white-reared ducklings. In Exp. II, ducklings pecked a white line. In a subsequent test, using a fully illuminated key, subjects in both groups responded more often to "green" (510, 530, 550, or 570 nanometers) than to "non-green" wavelengths (490, 589, 610, or 650 nanometers). Ducklings raised in monochromatic light preferred shorter "green" wavelengths than ducklings raised in white light. This difference between the "green" preferences for the two groups accounted for most of the differences between the gradients of wavelength generalization obtained from the two groups in Exp. I after training at 589 nanometers.     

Two-key concurrent responding: response-reinforcement dependencies and blackouts

Two-key concurrent responding was maintained for three pigeons by a single variable-interval 1-minute schedule of reinforcement in conjunction with a random number generator that assigned feeder operations between keys with equal probability. The duration of blackouts was varied between keys when each response initiated a blackout, and grain arranged by the variable-interval schedule was automatically presented after a blackout (Exp. I). In Exp. II every key peck, except for those that produced grain, initiated a blackout, and grain was dependent upon a response following a blackout. For each pigeon in Exp. I and for one pigeon in Exp. II, the relative frequency of responding on a key approximated, i.e., matched, the relative reciprocal of the duration of the blackout interval on that key. In a third experiment, blackouts scheduled on a variable-interval were of equal duration on the two keys. For one key, grain automatically followed each blackout; for the other key, grain was dependent upon a response and never followed a blackout. The relative frequency of responding on the former key, i.e., the delay key, better approximated the negative exponential function obtained by Chung (1965) than the matching function predicted by Chung and Herrnstein (1967).     

Effects of rate of reinforcement-time upon concurrent operant performance

Three experiments were conducted to investigate the theoretical reduction of rate and duration of reinforcement to their product, rate of reinforcement-time, under concurrent chain schedules. In Exp. I, rate of reinforcement-time was varied by varying rate of reinforcement delivery, holding duration of reinforcement availability constant; in Exp. II, rate of reinforcement-time was varied by holding rate of reinforcement delivery constant and varying duration of reinforcement availability; in Exp. III, rate of reinforcement-time was held constant by varying both rate and duration of reinforcement simultaneously and inversely. For all three experiments, both relative rate of responding and relative time spent in the initial link were found to match approximately the relative rate of reinforcement-time arranged in the terminal link. These data were interpreted as support for the notion that rate and duration of reinforcement may be functionally equivalent and reducible to a single variable, rate of reinforcement-time.     

Taking and the disruption of cooperation

Subjects could either cooperate or respond on a lower-paying individual task. In Exp. I and II, either subject could make a response that took $1.00 of the other's earnings whenever subjects chose to cooperate. The two experiments differed as to whether taking responses were effective continuously or intermittently. Both experiments showed that the opportunity to take disrupted cooperative behavior. Experiment III indicated that if taking was possible regardless of whether the subjects cooperated or responded on the individual task, subjects either cooperated or terminated the experiment.     

Shadows as sources of cues for distance of shadow-casting objects

Shadows are neglected sources of information about shadow-casting objects' distance (location). In an experiment using real shadows, participants judged the distance of two rods, either with shadows (illumination from the left) or without shadows. Without shadows, a thin rod raised slightly above the surface was incorrectly judged to be more distant than a thick rod, but with shadows the thin rod was accurately judged to be closer. For judgments to be correct, shadows had to overwhelm competing height and stimulus-size cues. Exp. II involved nonoverlapping shadows produced by a light placed in front of the rods. Again, without shadows the thin-elevated rod was incorrectly judged to be more distant, but with shadows it was correctly judged to be closer. Exp. III involved two sets of thick and thin elevated rods and frontal lighting. Judgments were accurate when shadows were present but inaccurate when shadows were absent. Experiments conducted through the American Psychological Society Web-research site replicated results of Exp. I, II, and III. A final Web experiment replicated results of the others, but with shadows produced by illumination from the right. Three properties of shadows--angles, interposition, and positioning--are possible sources of distance information associated with cast shadows.     

Autokinetic illusion as affected by suggestions of experimenter and observer.

Two experiments were done to examine whether an experimenter's suggestion and self-suggestion could affect the autokinetic illusion and to specify that effect. Exp. I compared the effect of a facilitative suggestion with a suppressive one, by measuring the moving latency, duration, frequency, and by analyzing the movement trace. Time and frequency did not detect any effects of marked individual differences. Trace analysis, on the other hand, showed that suggestions were effective in the expected direction for some subjects. Exp. II gave the suggestion for and against subjects' dominant direction of the movement and was designed to specify the effect. While effects indicated by time and frequency measures were not consistent, the movement trace showed the effect in suggested directions, which was more distinct for subjects whose nonsuggested illusion was not so markedly directed. These findings indicate that suggestion could affect the spatiotemporal aspect of the illusion, so the trace analysis may be useful for studies in this field.     

Concurrent schedules of reinforcement: effects of gradual and abrupt increases in changeover delay

Pigeons' pecks were maintained on concurrent variable-interval 1-min variable-interval 3-min schedules of reinforcement, with a changeover delay of 2 sec. When changeover delay was increased successively to 5.0, 7.5, and 12.5 sec (Exp. I) the actual relative rate of reinforcement for the variable-interval 3-min key decreased progressively for two birds, abruptly for two other birds, and the subjects devoted proportionately less of their time and responding to that key. However, the relative performance measures (relative time and relative responding) approximated the actual relative rate of reinforcement, with a maximum discrepancy of 11%, over all changeover delay values investigated. Experiment II attempted to lengthen response-run durations on the variable-interval 3-min key so that they were long enough to meet the changeover delay requirement at each new changeover delay value, by progressively increasing the changeover delay by 0.5-sec increments. With this procedure the actual relative rate of reinforcement approximated more closely the scheduled relative rate as changeover delay increased. As in Exp. I, relative performance measures approximated the actual relative reinforcement rate (maximum discrepancy 17%).     

Relations between patterns of responding and the presentation of stimuli under second-order schedules

Key-pecking behavior in the pigeon was maintained under second-order schedules in which food was presented after a variable number of 2-min fixed-interval components were completed. When either the same stimulus (Exp. I) or different stimuli (Exp. II) appeared on the key during consecutive components, and a stimulus that was occasionally paired with food was presented briefly at completion of each component, (1) patterns of positively accelerated responding were maintained during the components, and, (2) mean response rates were generally as high during the initial components of a sequence as during the later components. In both experiments, when the food-paired stimulus was omitted and either no stimulus or a stimulus never paired with food was presented at completion of each component, mean rates of responding increased, but patterns of positively accelerated responding were not maintained during individual components. When a food-paired stimulus was not presented at completion of the components, mean response rates in Exp. I were low during the initial components of a sequence and gradually increased during subsequent components; in Exp. II mean response rates were variable, and pauses and abrupt changes in response rates were typical.     

Anchor effects and figural aftereffects: a comparative psychophysical investigation.

Perceptual contrast effect was studied from two points of view, as a special anchor effect and as a special figural aftereffect. Two experiments were conducted to investigate the influence of stimulus onset asynchrony on contrast and assimilation effects, induced and measured by different psychophysical methods. Stimuli were circular beams of light projected on screens (Delboef type of illusion). When anchor and series stimuli were shown and the latter were judged by means of a rating scale, stimulus onset asychrony had no substantial influence on the contrast effect (Exp. I). When the constant method was applied, however, the asynchrony altered the shape of the contrast effect considerably (Exp. II).     

Effects of group contingent events upon classroom noise

The first study investigated a group control procedure for suppression of excessive sound-intensity levels in a regular public school classroom. Reinforcement consisted of a 2-min addition to the class gym period and a 2-min break after maintenance of an unbroken 10-min quiet period as monitored on a decibel meter. Transgressions of the sound limit (42 decibels) resulted in a delay of reinforcement by the resetting of the timer to the full 10-min interval. The results indicated that these procedures were highly effective in suppression and control of sound intensities. The second experiment utilized a similar procedure coupled with a procedure of eliminating out-of-seat behavior. Experiment III studied the effects of Exp. II procedures on a single student's out-of-seat behavior rate. All procedures were found effective.     

The reinforcement of four interresponse times in a two-alternative situation

Pigeons pecked for food in a two-key procedure. A concurrent variable-interval variable-interval schedule of reinforcement for two classes of interresponse times was arranged on each key. A visual stimulus set the occasion for potential reinforcement of the four operant classes: shorter and longer interresponse times on left and right keys. In Exp. I, the relative frequency of respones on a key equalled the relative frequency of reinforcement on that key. In Exp. II, the relative frequency of an interresponse time equalled the relative reciprocal of its length. In Exp. III, the relative frequency of an interresponse time was a monotonically increasing function of its relative frequency of reinforcement. These functions relating the relative frequency of an interresponse time to its relative length and to its relative frequency of reinforcement were the same as if there had been no second key. Also, the distribution of responses between keys was independent of the relative frequency of an interresponse time on either key. Experiment IV replicated Exp. I except that choices between keys were controlled by a stimulus that signalled the availability of reinforcement on the right key. A comparison of Exp. I and IV suggested that the relative frequency of an interresponse time on one key generally was independent of behavior on the other key, but that the number of responses per minute on a key did depend on behavior on the other key.     

Blood glucose and brain function: interactions with CNS cholinergic systems

We recently found that glucose injections attenuate amnesia and hyperactivity produced by scopolamine, a muscarinic antagonist. The present study examined whether glucose would augment behavioral effects produced by a muscarinic agonist, physostigmine. In experiment I, doses were first determined for which neither glucose (10 mg/kg) nor physostigmine (0.05 mg/kg) altered scopolamine-induced hyperactivity. However, combined glucose-physostigmine injections significantly reduced scopolamine hyperactivity. Experiment II evaluated the effects of glucose on physostigmine-induced tremors. Glucose (10, 100, and 250 mg/kg) or saline injections were given 20 min before physostigmine injections (0.4 or 0.05 mg/kg). Observations of glucose effects on the severity of physostigmine-induced tremors were then obtained at 5-min intervals for 25 min after physostigmine injections. Glucose (100 mg/kg) significantly facilitated the onset of tremors when injected before either dose of physostigmine, and augmented (at 100 and 250 mg/kg) tremor severity when injected before the lower dose of physostigmine. These findings indicate that glucose can facilitate the actions of a cholinergic agonist on two behaviors, locomotor activity and tremors, adding support to the view that circulating glucose levels can modulate central cholinergic function. More generally, the results provide additional evidence that circulating glucose levels can influence brain function.     

Spontaneous eyeblinks elicited by vertical eye movements

Two experiments were carried out to examine the relationship between eyeblinks and eye movements under a visual search task. Exp. I showed that the vertical eye movements brought about slightly more eyeblinks than the horizontal ones. In Exp. II, the vertical eye movements were accompanied with significantly more frequent eyeblinks than the horizontal ones. Upward saccadic eye movements especially were associated with the more frequent eyeblinks than the downward ones. These results suggested a possible relationship between the eyeblinks and Bell's phenomenon. However, the comparison of eyeblink rates between eye-movement and the no-eye-movement conditions in Exp. II indicated that in the latter condition eyeblinks were significantly more frequent than in the former condition. Some psychological factors were suggested as likely important determinants of the frequency of eyeblinks.     

Temporal constraint on choice: Sensitivity and bias in multiple schedules

In multiple schedules of reinforcement, ratios of responses in successive components are relatively insensitive to ratios of obtained reinforcers. An analysis is proposed that attributes changes in absolute response rates to concurrent interactions between programmed reinforcement and extraneous reinforcement in other components. The analysis predicts that ratios of responses in successive components vary with reinforcer ratios, qualified by a term describing the reinforcement context, that is, programmed and extraneous reinforcers. Two main predictions from the analysis were confirmed in an experiment in which pigeons' responses were reinforced in the components of a multiple schedule and analog extraneous reinforcement was scheduled for an alternative response in each component. Sensitivity of response and time ratios to reinforcer ratios in the multiple schedules varied as a function of the rate of extraneous reinforcers. Bias towards responding in one component of the multiple schedule varied as an inverse function of the ratios of extraneous reinforcer rate in the two components. The data from this and previous studies of multiple-concurrent performance were accurately predicted by our analysis and supported our contention that the allocation of behavior in multiple-schedule components depends on the relative values of concurrently-available reinforcers within each component.