Responding under sequence schedules of electric shock presentation

Lever pressing by squirrel monkeys was examined under second-order schedules of electric shock presentation in which different discriminative stimuli were associated with consecutive components (sequence schedules). Components were always two-minute fixed-interval schedules, and three different overall schedules were studied. Under an overall eight-minute fixed-interval schedule, the first component completion after at least eight minutes had elapsed produced electric shock. The number of components actually completed ranged from one to four; thus, different discriminative stimuli were occasionally associated with electric shock presentation. Under an overall “yoked” variable-ratio schedule, electric shock was presented after completion of a variable number of components; the required number and the distribution of components were matched to those obtained under the overall eight-minute fixed-interval schedule. Under an overall fixed-ratio schedule, electric shock was presented after completion of four components (chained schedule). Under all three sequence schedules, responding in early components was characterized by a pause followed by a single response after the end of the two-minute interval; responding in later components was characterized by a shorter pause followed by positively accelerated responding. Manipulation of overall schedules of shock presentation in these complex behavioral situations produced changes in responding comparable to those ordinarily obtained after similar manipulation of dependencies under both single and second-order schedules of food presentation. These experiments extend the range of conditions and levels of complexity under which responding can be maintained by presentation of electric shock.     

Maintenance and suppression of responding under schedules of electric shock presentation

In squirrel monkeys previously trained under a continuous avoidance schedule, characteristic patterns of responding were maintained under a 3-min variable-interval schedule of shock presentation (response-produced shock). Responding in the presence of a periodically presented stimulus, the termination of which coincided with the delivery of a response-independent electric shock (Estes-Skinner procedure), was not reliably affected. When shocks followed every response during certain signalled portions of the session, and were presented under the variable-interval schedule during the rest of the session (multiple 1-response fixed-ratio, 3-min variable-interval schedule of shock presentation), responding was suppressed during the fixed-ratio component and maintained during the variable-interval component. Environmental consequences do not have immutable properties, and may either support or suppress behavior, depending on the schedule of presentation.     

Schedules of presentation and temporal distinctiveness in human memory

Recency, in remembering a series of events, reflects the simple fact that memory is vivid for what has just happened but deteriorates over time. Theories based on distinctiveness, an alternative to the multistore model, assert that the last few events in a series are well remembered because their times of occurrence are more highly distinctive than those of earlier items. Three experiments examined the role of temporal and ordinal factors in auditorily and visually presented lists that were temporally organized by distractor materials interpolated between memory items. With uniform distractor periods, the results were consistent with Glenberg's (1987) temporal distinctiveness theory. When the procedure was altered so that distractor periods became progressively shorter from the beginning to the end of the list, the results were consistent for only the visual modality; the auditory modality produced a different and unpredicted (by the theory) pattern of results, thus falsifying the claim that the auditory modality derives more benefit from temporal information than the visual modality. We distinguish serial order information from specifically temporal information, arguing that the former may be enhanced by auditory presentation but that the two modalities are more nearly equal with respect to the latter.     

Responding maintained under fixed-interval and fixed-time schedules of electric shock presentation

Following initial histories under a schedule of electric shock postponement, lever pressing in squirrel monkeys was maintained under fixed-interval and fixed-time schedules of electric shock presentation. No difference in either rate or pattern of responding was obtained when these schedules were presented as components of a multiple schedule. When they were presented singly for long periods of time, the fixed-interval schedule consistently maintained a higher response rate than the fixed-time schedule. The pattern of responding under both schedules was similar, typically consisting of a pause at the beginning of each interval followed by either a steady or a positively accelerating rate of responding. The results suggest that the response-shock dependency is of critical importance in the maintenance of high rates of responding under schedules of electric shock presentation, and support the general view that such responding may be conceptualized as operant behavior under control of many of the same variables that control responding under comparable schedules of food or water reinforcement.     

Schedules using noxious stimuli. II: low intensity electric shock as a discriminative stimulus

The presence or absence of pulses of low intensity electric shock was used as a discriminative stimulus to control responding under fixed ratio reinforcement in the squirrel monkey. Initially brief periods of nonreinforcement were lengthened only when discriminative control was evident. Discriminative control was studied by (1) varying the duration of nonreinforcement periods; (2) reversing the stimulus conditions correlated with reinforcement and nonreinforcement periods; and (3) determining the minimum shock intensity necessary to maintain discriminative control. Stimulus control was not reliably affected by d-amphetamine, chlorpromazine, or morphine. The discriminative control by pulses of low intensity electric shock was similar to that by other discriminative stimuli, except that the control developed slowly and was better when the pulsing shock was correlated with reinforcement than when correlated with nonreinforcement.     

Responding under fixed-ratio and multiple fixed-interval fixed-ratio schedules of electric shock presentation

Squirrel monkeys, initially trained under a schedule of electric shock postponement and then under fixed-interval schedules of electric shock presentation, were studied under multiple fixed-interval fixed-ratio and under fixed-ratio schedules of shock presentation. Under the fixed-interval (10-min) component of the multiple schedule, a pause was followed by a gradual increase in responding to a rate maintained until shock presentation; under the fixed-ratio (3-, 10-, or 30-response) component of the multiple schedule, a brief pause was typically followed by a relatively high and uniform rate of responding until shock was presented. When the 60-sec timeout periods, which usually followed shock presentation, were eliminated from the multiple schedule for one monkey, responding was only transiently affected. In the one monkey studied, responding was maintained under a fixed-ratio schedule alone (with timeout periods), but rates of responding were lower than under the fixed-ratio component of the multiple schedule. Characteristic patterns of responding, similar to those engendered under schedules of food presentation or shock termination, can be maintained under fixed-ratio schedules of shock presentation; further, patterns of responding can be controlled by discriminative stimuli in multiple schedules.     

Responding in the cat maintained under response-independent electric shock and response-produced electric shock

Key-pressing responses in the cat were maintained under conditions in which brief electric shock was first postponed by responses (avoidance), then periodically presented independently of responses, and finally produced by responses on a fixed-interval schedule of 15 min (FI 15-min). A steady rate of responding occurred under shock avoidance and under response-independent shock; positively accelerated responding was engendered by the FI 15-min schedule. A second experiment studied responding under second-order schedules composed of three FI 5-min components. Responding was suppressed when a stimulus was presented briefly at completion of each FI 5-min component and a shock followed the brief stimulus at completion of the third component. Responding was maintained when each of the first two components was completed either with or without presentation of a brief stimulus and a shock alone was presented at completion of the third FI 5-min component.     

Fixed-interval schedules of electric shock presentation: extinction and recovery of performance under different shock intensities and fixed-interval durations

In squirrel monkeys responding under a schedule in which responding postponed the delivery of electric shock, the presentation of response-dependent shock under a fixed-interval (FI) schedule increased the rate of responding. When the schedule of shock-postponement was eliminated, so that the only shocks delivered were those produced by responses under the FI schedule, a pattern of positively accelerated responding developed and was maintained over an extended period. When responses did not produce shocks (extinction), responding decreased. When shocks were again presented under the FI schedule, the previous pattern of responding quickly redeveloped. In general, response rates were directly related to the intensity of the shock presented, and inversely related to the duration of the fixed-interval. These results raise fundamental questions about the traditional classification of stimuli as reinforcers or punishers. The basic similarities among FI schedules of food presentation, shock termination, and shock presentation strengthen the conclusion that the schedule under which an event is presented and the characteristics of the behavior at the time the event is presented, are of overriding importance in determining the effect of that event on behavior.     

Changing the perception of behavioral properties by subliminal presentation

Profiles designed by Pittenger and Shaw were used in a tachistoscopic experiment. Subjects were asked to make estimates of age of a profile of a 10-yr.-old boy preceded subliminally by an older (old group) or younger (young group) profile or by a blank card (control group). Results show the mean estimate of the young group to be significantly smaller than that of the control group. The mean estimate of the old group was not significantly greater than that of the control group. The results are discussed in the framework of the debate on direct versus indirect perception. Marcel's 1983 data and the present results indicate that higher level perceptual processing (the perception of behavioral properties) can precede lower level perceptual processing (the perception of physical properties). By assuming that people do perceive directly the behavioral properties of an event, the direct approach avoids the danger of putting too much emphasis on intelligence in perception and at the same time avoids the homunculus trap.     

Painfulness decreases the discriminability of electric shock

Two experiments were designed to investigate the relation between the reported painfulness and the discriminability of pairs of electric shocks for which the ratio between the higher and the lower intensity was held constant. In both experiments, subjects first gave category ratings of the painfulness of single shocks in the range 40 to 4.8 mA. Then, in a discrimination experiment, they were required to identify the stronger of a pair of intensities presented in succession. The proportion of correct responses (Experiment 1) or the proportion of area under the receiver operating characteristic (Experiment 2) increased between a low-intensity pairing and a medium-intensity pairing and decreased between a medium-intensity pairing and a high-intensity pairing for subjects who rated the highest intensities as strongly painful. Subjects who gave moderate- or weak-pain ratings for the high-intensity shocks showed no significant increase or decrease in accuracy between the medium- and high-intensity pairings. Time-order errors were observed in Experiment 1. The proportion of trials on which the second stimulus of the pair was identified as the stronger increased monotonically as a function of stimulus magnitude. The results are discussed in the context of psychological assessment of analgesic procedures.     

Conditioned-aversive aspects of electric shock

Two experiments were reported in which it was observed that a weak shock became more aversive as a result of appropriate pairing of that stimulus with a stronger shock. The enhanced aversiveness of the weak shock was reflected in Experiment 1 by an apparent increase in the reinforcement provided by response-contingent termination of that shock. In Experiment 2, the weak shock was observed to be more suppressive of a consummatory-response baseline following appropriate pairings of the weak and strong shocks. The results of these studies were discussed in terms of their implications for certain aversive-conditioning situations in which shocks may serve, in part, as conditioned stimuli.     

Response-dependent shock in second-order fixed-ratio schedules of food presentation

Three pigeons key pecked under second-order schedules in which the completion of two successive fixed-ratio 50 components constituted a reinforcement cycle. Tandem, chained, and brief-stimulus second-order schedules were studied when completion of the initial fixed-ratio 50 component delivered brief intense electric shock in every nth reinforcement cycle and n assumed values between one and nine. During sessions without shock, the brief-stimulus (unpaired with food) schedule generated higher rates of responding in the initial component than did the tandem schedule. Electric shock engendered increased time to the fifth response and a repeated pause-run pattern of not responding and responding, particuuarly in the initial component, even with shock scheduled in every ninth reinforcement cycle. The results were consistent with those reported for shock of a shorter duration scheduled in every reinforcement cycle. The overall rate of responding decreased as a function of increasing shock density and was lower in brief-stimulus than in tandem schedules.     

Illusion of control and behavioral control attempts in obsessive-compulsive disorder

The present research used the illusion-of-control paradigm to examine the relationships among obsessive-compulsive disorder (OCD) symptoms, behavioral control attempts, and illusory sense of control. Participants were presented with a preprogrammed sequence of aversive and neutral visual stimuli and were encouraged to attempt to control the sequence with keyboard presses. Participants rated their perceived level of control 3 times during the task. In addition, the authors used the repetitiveness of keyboard presses as a measure of rigid, compulsive-like behavior. In Study 1, this procedure was administered to a sample of 55 students who also completed measures of OCD and depression. In Study 2, the task was administered to 22 participants with OCD and 22 matched participants without OCD. In line with predictions, OCD symptoms were correlated with higher illusory sense of control and with more repetitive behavioral control attempts. The authors discuss the central role of control in OCD and specifically the relationships between need for control and compulsive rituals, which may be conceptualized as means for achieving an illusory sense of control over stressful life events.     

Persistence of acquired behavioral control in the context of imprinting

Newly hatched Khaki Campbell ducklings (Anas platyrhynchos domesticus) were exposed to a moving object that immediately suppressed distress vocalizations occurring in a novel environment. The static visual and auditory features of this object acquired the ability to suppress distress vocalizations after eight 20-min sessions of exposure to the object in motion. The acquired suppressive properties of these features were found to persist throughout thirty 20-min sessions given over 10 days. During these sessions, the ducklings were continually exposed to the static features in the absence of visual movement. In a second experiment, the ability of these features in the absence of visual movement. In a second experiment, the ability of these features to serve as reinforcement for a pecking response was shown to persist for up to 56 hr. In one duckling, presentations of the static visual features did not maintain pecking behavior. However, it was shown that pecking responses could be re-instated in this duckling by introducing novel stimuli to the environment.