Frances K. McSweeney

Habituation revisited: an updated and revised description of the behavioral characteristics of habituation.

The most commonly cited descriptions of the behavioral characteristics of habituation come from two papers published almost 40 years ago [Groves, P. M., & Thompson, R. F. (1970). Habituation: A dual-process theory. Psychological Review, 77, 419-450; Thompson, R. F., & Spencer, W. A. (1966). Habituation: A model phenomenon for the study of neuronal substrates of behavior. Psychological Review, 73, 16-43]. In August 2007, the authors of this review, who study habituation in a wide range of species and paradigms, met to discuss their work on habituation and to revisit and refine the characteristics of habituation. This review offers a re-evaluation of the characteristics of habituation in light of these discussions. We made substantial changes to only a few of the characteristics, usually to add new information and expand upon the description rather than to substantially alter the original point. One additional characteristic, relating to long-term habituation, was added. This article thus provides a modern summary of the characteristics defining habituation, and can serve as a convenient primer for those whose research involves stimulus repetition.

Sensitization–habituation may occur during operant conditioning.

Operant response rates often change within experimental sessions, sometimes increasing and then decreasing. The authors attribute these changes to sensitization and habituation to aspects of the experimental situation presented repeatedly (e.g., reinforcers) or for a prolonged time (e.g., the experimental enclosure). They describe several empirical similarities between sensitization-habituation and within-session changes in operant responding. They argue that many alternative explanations for within-session changes in operant responding can be dismissed. They also examine some implications of linking the literatures on habituation and operant responding. Because responding follows a similar pattern in several other cases (e.g., human vigilance, classical conditioning, and unconditioned responding), 2 relatively simple processes may be responsible for the temporal patterning of behavior in a wide variety of situations. We observed large changes in response rate within experimental sessions when subjects (e.g., rats) responded on operant conditioning procedures (e.g., McSweeney, Hatfield, & Allen, 1990). In many of our experiments, response rates increased to a peak and then decreased. In other experiments, response rates increased without decreasing or decreased without increasing. Figure 1 contains an example of each of these types of changes. The top represents results for rats pressing levers on multiple variable interval (VI) 60-s VI 60-s schedules; the middle, the results for rats pressing levers on a VI 15-s schedule; and the bottom, the results for pigeons pecking keys on a variable ratio (VR) 15 schedule. Each graph represents the proportion of total-session responses during successive 5-min intervals in the session. Throughout this article, we calculated proportions by dividing the number of responses during a 5-min interval by the total number of responses during the session. Although within-session changes in operant responding have been observed in the past (e.g., McSweeney & Roll, 1993), these changes have been treated as problems to control by procedures, such as giving warmup trials (e.g., Hodos & Bonbright, 1972) or time to adapt to the apparatus (e.g., Papini & Overmier, 1985), rather than as phenomena to study. Further consideration suggests that within-session changes deserve study in

Concurrent schedule responding as a function of body weight

Five pigeons pecked for food reinforcement on several concurrent schedules. Their body weights were varied from 80% to 110% of their free-feeding weights. A number of predictions of the equations proposed by Herrnstein (1970) were tested. As predicted, the relative rate of responding equalled the relative rate of reinforcement for all subjects, on all schedules, at all body weights. And, as predicted, the overall rates of responding on the components of a concurrent schedule were slower than the local rates of responding on the components of an identical multiple schedule. Contrary to prediction, the total rate of responding generated by the concurrent schedules did not increase with increases in the total rate of reinforcement they provided. And, contrary to prediction, the k parameter did not remain constant, and the R0 parameter did not increase with increases in body weight. It was concluded that Herrnstein’s matching law and his interpretation of the m parameter are correct but that the interpretations of k and R0 require further investigation.

Prediction of concurrent keypeck treadle-press responding from simple schedule performance

Four pigeons pecked keys and pressed treadles for food reinforcers delivered by several variable-interval schedules of reinforcement. Then the subjects responded on several concurrent schedules. Keypecking produced reinforcers in one component, and treadle-pressing produced reinforcers in the other. The changeover delay, which prevented reinforcement after all switches from one response to the other, was 0, 5, or 20 sec long. An equation proposed by Kerrnstein (1970) described the rates of treadle-pressing and keypecking emitted during the variable-interval schedules. The k parameter of this equation was larger for keypecking than for treadle-pressing. The R0 parameters were not systematically different for the two responses. The rates of keypecking and treadle-pressing emitted during the components of the concurrent schedules correlated with, but were not equal to, the rates of responding predicted by Herrnstein’s equation and the subject’s simple schedule responding. The ratios of the rates of responding emitted during, and the ratios of the time spent responding on, the components of the concurrent schedules conformed to an equation proposed by Baum (1974), but not to Herrnstein’s equation.

Modeling influences on eating behavior

Abstract Some aspects of social influence on eating behavior have been examined but no studies have looked at direct influences of one persons eating behavior on that of another. Two experiments assessed whether people model rate of eating and amount of food consumed by another person. In Experiment I, female college students ate a standardized luncheon with a confederate-model peer, who ate her lunch at a predetermined fast (12 min) or slow (25 min) rate. Subjects who ate with fast-eating confederate-models consumed their lunches at a significantly faster rate than subjects who ate with slow-eating confederate-models. In Experiment II, same and opposite sex pairs of subjects and confederate-models participated in a “cracker tasting” task. The confederate-model ate either a high (40) or low (10) number of crackers in 7 min. Subjects eating with a high consumption male confederate-model ate more crackers than subjects who ate with a low consumption male or female confederate-model. But, subjects who ate with a high consumption female confederate-model did not differ from the other groups in number of crackers eaten. These findings may be important for treating obesity, if modeling also occurs in natural situations.

DO ANIMALS SATIATE OR HABITUATE TO REPEATEDLY PRESENTED REINFORCERS

Operant response rates may decrease within experimental sessions. The most likely explanation for the decrease is that satiation or habituation reduces the effectiveness of the repeatedly presented reinforcer. We argue that, contrary to intuition, both empirical and formal arguments favor habituation over satiation. Attributing the decreases in operant responding partly to habituation challenges the traditional assumption that habituation alters only reflexive behavior and does not occur to biologically significant stimuli. It preserves common terminology during operant and classical conditioning and when appetitive and aversive stimuli are used. It may provide a relatively general description of temporal changes in behavior in a wide variety of situations and may help to integrate motivational variables into theories of conditioning.

Habituation of salivation and motivated responding for food in children

Repeated presentation of food cues results in habituation in adults, as demonstrated by a decrement in salivary responding that is reversed by presenting a new food cue in adults. Food reinforced behavior in animals shows the same pattern of responding, with a decrease in responding to obtain the food, followed by a recovery of responding when a new food is presented. The present study assessed whether children would show the same pattern of a decrement of food reinforced responding followed by recovery of responding when a new food is presented for both salivation and food reinforcement tasks. Subjects were assigned to one of two groups that differed in the trial that the new food stimulus was presented to ensure recovery was specific to the introduction of the new food stimulus. In the salivation task, subjects were provided repeated olfactory presentations of a cheeseburger with apple pie as the new food stimulus, while in the food reinforcement task subjects worked for the opportunity to consume a cheeseburger, followed by the opportunity to work for consumption of apple pie. Subjects in both groups showed a decrement in salivary and food reinforced responding to repeated food cues followed by immediate recovery of responding on the trial when a new food was presented. Subjects increased their energy intake by over 30% in the food reinforcement task when a new food was presented. These results are consistent with the general process theory of motivation that suggests that changes in food reinforced responding may be due in part to habituation.

Within-session responding as a function of post-session feedings.

Ten rats pressed levers or keys for food reinforcers delivered by a multiple variable interval schedule. The delay between the end of the session and the delivery of a post-session feeding varied from 0 to 240 minutes. Contrary to the results reported by Bacotti (1976), response rates were not significantly higher when post-session feedings were delayed than when they were immediate. Response rates also increased and then decreased within the session, regardless of the delay to post-session feedings. These results suggest that subjects do not always integrate rewards across locations. Therefore, theories need not always include the temporal location of post-session feedings in the context of variables that determines responding within the session. Experiments must also take care to ensure that changes in response rates within the session do not confound the interpretation of their results.

The generality of within-session patterns of responding : rate of reinforcement and session length

Rats and pigeons responded for food delivered according to multiple schedules. The session length varied from 10 to 120 min, and the programmed rate of reinforcement varied from 15 to 240 reinforcers per hour. Response rates usually changed systematically within experimental sessions. For both rats and pigeons, responding reached a peak after an approximately constant amount of time since the beginning of the session, regardless of session length. When rats, but not pigeons, served as subjects, the peak rates of responding occurred later in the session and the within-session changes were smaller for lower than for higher rates of reinforcement. The similarities between the results for rats and for pigeons when session length varied suggest that at least one of the factors that produces the within-session changes in responding is shared by the present species, responses, and reinforcers. The differences in results when rate of reinforcement varied are more difficult to interpret.

Satiety contributes little to within-session decreases in responding

Abstract Responding often increases to a peak and then decreases within experimental sessions when subjects respond during operant conditioning procedures. The present experiments tested three implications of the idea that “satiation” produces the late-session decreases in responding. In Experiment 1, the late-session decreases were not altered when the caloric density of the reinforcer changed. In Experiment 2, the late-session decreases were not altered by changing the subjects state of deprivation, or the amount of food they were intubated with before the session. In Experiment 3, the late-session decreases were not altered by changing the size of the reinforcer by a factor of 3. The decreases began earlier and were steeper when reinforcers were 5 times as large. These results indicate that satiation, as operationalized in these experiments, does not cause the late session decreases in responding. Satiation may alter these decreases if large amounts of reinforcement are delivered.