Within-session decreases in operant responding as a function of pre-session feedings. by Eric S. ... more Within-session decreases in operant responding as a function of pre-session feedings. by Eric S. Murphy , Frances K. McSweeney , Benjamin P. Kowal During the past decade, the phenomenon of within-session changes in operant responding has receive.
The current research attempted to decrease individuals' rates of delay discounting by introducing... more The current research attempted to decrease individuals' rates of delay discounting by introducing decoys that are similar but inferior to delayed rewards. Two experiments in the current study compared patterns of delay discounting generated by repeated choices between two hypothetical monetary rewards in the absence or presence of a decoy. Binary questionnaires (i.e., decoy absent) included questions with two options: a smaller-sooner (SS) reward and a larger-later (LL) reward. Trinary questionnaires (i.e., decoy present) included questions with three options: an SS reward, an LL reward, and a decoy. If an option is at least as rewarding on every dimension of value as an alternative and the option is more rewarding than an alternative on at least one dimension, then the option is considered to dominate the alternative (Wedell, 1991). The first experiment assessed the influence of decoys dominated by LL rewards (LL − decoys), which were constructed to be similar (on the dimension of amount) but inferior (on the dimension of delay) to LL rewards. The second experiment examined the effects of counterbalancing the order of binary and trinary questionnaires. In the first experiment, participants discounted to a lesser degree when LL − decoys were present as compared to when they were absent. In the second experiment, participants only discounted to a lesser degree on trinary questionnaires with LL − decoys when they had not previously completed binary questionnaires. Patterns of discounting generated by binary questionnaires were similar to those generated by trinary questionnaires when decoys are present; however, the degree to which individuals discounted delayed rewards was affected by the number of and type of options that were available. The current results join previous evidence suggesting that rates of delay discounting are sensitive to a variety of contextual influences.
One of the hallmarks of drug addiction is a limitation of the temporal horizon of events that aff... more One of the hallmarks of drug addiction is a limitation of the temporal horizon of events that affect the behavior of drug users. The purpose of this experiment was to examine the time period over which smoking was influenced by an earlier opportunity to smoke. Baseline sessions measured how much was smoked in a current opportunity when it was preceded by a two-hour wait time in which no smoking was allowed. Following the baseline phase, we examined the effects of temporal distance when an earlier opportunity to smoke (upon completion of a FR100) preceded current smoking (upon completion of a PR). Temporal distance between these two opportunities to smoke was varied from 0 min to 120 min. We found that current smoking for the group was reduced from baseline levels when the temporal distance was 0 min. At temporal distances ranging from 30 min to 90 min, the individual's smoking returned to levels that were similar to baseline. Breakpoints were also a function of previous smoking, and latencies to first puff of the session followed a similar trend. These findings provide evidence of the limited temporal horizons related to smoking bouts of smokers and may provide a useful measure for metabolism differences across populations. In addition, we suggest that the quantitative description of satiety provided by our procedures may validate drug replacement therapies involved in cessation treatments.
Experimental and Clinical Psychopharmacology, 2005
The authors argue that drug taking is an operant behavior that is reinforced by the drug itself. ... more The authors argue that drug taking is an operant behavior that is reinforced by the drug itself. The effectiveness of a drug as a reinforcer is modulated by sensitization and habituation to the drug as it is consumed. According to this model, drug taking stops when habituation reduces the ability of the drug to reinforce its own consumption. Drug taking resumes when spontaneous recovery restores the effectiveness of the drug as a reinforcer. This parsimonious model provides a framework for understanding many findings in the drug literature, including acute and chronic tolerance, the effect of deprivation on consumption, the contextual specificity of tolerance, polydrug abuse, cross-sensitization between stress and drugs, behavioral sensitization, priming, and reinstatement. Although this model cannot explain all aspects of drug taking (e.g., the effect of cognitive manipulations), it has many implications for understanding and controlling human drug consumption and addiction.
Two algorithms are commonly applied in computerized temporal discounting procedures (Decreasing A... more Two algorithms are commonly applied in computerized temporal discounting procedures (Decreasing Adjustment and Double-Limit Algorithms); however, the degree to which the two algorithms produce similar patterns of discounting is unknown. The present experiment compared the two common algorithms across sign (gains and losses) and magnitude ($10 and $1000) conditions. Twenty participants made choices between larger later and smaller sooner alternatives that were presented by each of the algorithms in separate conditions. Strong correlations were found between the two measures; however, the Decreasing Adjustment Algorithm tended to produce lower indifference points and higher rates of discounting than the Double-Limit Algorithm. Both algorithms found significant magnitude effects. Less consistent results were found when comparing the two algorithms across sign. The present results suggest that researchers should apply caution when making comparisons between outcomes of delay discounting studies that have used the two different algorithms. However, the interpretation of findings from individual studies is probably not strongly affected by the use of different computer algorithms.
The seemingly irrational behavior exhibited by individuals with addiction may be understood by co... more The seemingly irrational behavior exhibited by individuals with addiction may be understood by considering their temporal horizon. In this paper, we reviewed published literature and current research concerning how delay discounting, a measure of temporal horizon, has been employed to understand addiction. Specifically, studies of delay discounting among addicted individuals and other psychiatric populations, current controversies in the delay discounting literature, and new developments were reviewed. Addicted individuals discount the long-term consequences of their behavior at a higher rate than matched controls. Current controversies illustrate the need for continued research. Given the rising interest in using delay discounting to understand addictive behaviors, in terms of both overt behavior and at the level of brain activity, we believe research in this field will continue to produce substantial progress for the next several years.
Nineteen nicotine-deprived cigarette smokers received monetary rewards for each minute they choos... more Nineteen nicotine-deprived cigarette smokers received monetary rewards for each minute they choose not to initiate smoking in 2-hour laboratory sessions followed by a 30-min period of enforced abstinence from smoking. Reinforcer amounts were delivered according to one of three schedules: increasing, decreasing, and constant. Relapse time (time until first smoke) was shortest in the decreasing condition, longest in the increasing condition, and intermediate in the constant condition. All differences were significant except in the constant-decreasing comparison. The relationships between a battery of baseline assessments and relapse times were examined. Relapse times were predicted by delay-discounting coefficients (k) for $10 and $1000 in money, and for $1000 of cigarettes. Relapse times were also predicted by the number of cigarettes smoked daily and a Wisconsin Card Sorting Test score. Performance on the Stroop Task and the Fagerström Test for Nicotine Dependence differentiated participants dichotomized into those who relapsed "earlier" in sessions versus those who first smoked "later." Variability on some scores from smoking-urges and affect questionnaires administered after smoking-room sessions was explained by measures related to in-session nicotine intake. Results are discussed as they relate to contingency-management procedures, predictors of relapse, and the competing neuro-behavioral decision systems theory of addiction.
We review behavioral-and neuroeconomic research that identifies temporal discounting as an import... more We review behavioral-and neuroeconomic research that identifies temporal discounting as an important component in the development and maintenance of drug addiction. First we review behavioral economic research that explains and documents the contribution of temporal discounting to addiction. This is followed with recent insights from neuroeconomics that may provide an explanation of why drug dependent individuals discount the future. Specifically, neuroeconomics has identified two competing neural systems that are related to temporal discounting using brainimaging techniques that examine the relative activation of different brain regions for temporal discounting. According to the competing neural systems account, choices for delayed outcomes are related to the prefrontal cortex (i.e., the "executive system") and choices for immediate outcomes are related to the limbic brain regions (i.e., the "impulsive system"). Temporal discounting provides a useful framework for future imaging research, and suggests a novel approach to designing effective drug dependence prevention and treatment programs.
The present experiment examined whether habituation contributes to within-session decreases in op... more The present experiment examined whether habituation contributes to within-session decreases in operant responding for water reinforcers. The experiment asked if this responding can be dishabituated, a fundamental property of habituated behavior. During baseline, rats' lever pressing was reinforced by water on a variable interval 15-s schedule. During experimental conditions, rats responded on the same schedule and a new stimulus was introduced for 5 min at 15, 30 or 45 min into the 60-min session. The new stimulus was extinction, continuous reinforcement or flashing lights in different conditions. Rate of responding primarily decreased within the session during baseline. Introducing a new stimulus sometimes suppressed (extinction, continuous reinforcement) and sometimes increased (flashing lights) responding while it was in effect. The new stimulus increased responding after it ended and before it was presented in the session. The results are incompatible with the idea that non-habituation satiety factors (e.g., cellular hydration and blood volume) contributed to within-session changes in responding. These satiety factors should increase with increases in consumption, decrease with decreases in consumption and remain constant with constant consumption of water. Nevertheless, all stimulus changes increased operant responding for water. These results support the idea that habituation contributes to within-session decreases in responding for water reinforcers.
Experimental and Clinical Psychopharmacology, 2006
This study examined whether habituation, a decrease in responsiveness to a repeatedly presented s... more This study examined whether habituation, a decrease in responsiveness to a repeatedly presented stimulus, occurs to ethanol reinforcers in alcohol-preferring (P) rats. Three fundamental properties of habituation were evaluated: generality, spontaneous recovery, and dishabituation. In each experiment, P rats' lever pressing was reinforced by 10% ethanol on a variable-interval 15-s schedule during 50-min sessions. Experiment 1 evaluated the generality of habituation to repeatedly presented stimuli by using ethanol and water reinforcers. Rates of responding were higher for ethanol than they were for water. Additionally, the within-session patterns of responding differed for each reinforcer, suggesting that the pattern of responding was specific to the exact nature of the repeatedly presented reinforcer. Experiment 2 examined spontaneous recovery, an increase in responsiveness to a habituated stimulus when that stimulus is not presented for a time, by separating experimental sessions by 5 min, 2 hr, or 24 hr. Early-session rates of responding during Session 2 were slower than the corresponding rates during Session 1 when sessions were separated by 5 min or 2 hr. Response rates and within-session patterns of responding during Sessions 1 and 2 were similar when sessions were separated by 24 hr. Experiment 3 tested for dishabituation, a restoration of responsiveness following the presentation of an extraneous stimulus, by presenting a tone or a light 24 min and 55 s into the session. Rates of responding temporarily increased after the tone was presented. The results of these experiments support the idea that habituation contributes to the regulation of ethanol consumption.
Pigeons’ keypecking was reinforced by food on baseline schedules of multiple variable interval (V... more Pigeons’ keypecking was reinforced by food on baseline schedules of multiple variable interval (VI)x VIx and on contrast schedules of multiple VIx VIy. Deprivation of food was varied by maintaining subjects at 75%, 85%, and 95% (±2%) of their free-feeding weights. Positive and negative behavioral contrast were observed. The size of the contrast was not systematically altered by changes in deprivation. Positive and negative contrast were both larger later in the session than they were earlier. Withinsession decreases in responding were steeper for the baseline than for the contrast schedules for positive contrast. Within-session decreases were steeper for the contrast than for the baseline schedules for negative contrast. These results were predicted by the idea that different amounts of habituation to the reinforcer during the baseline and contrast schedules contribute to behavioral contrast. The results show that contrast occurs under conditions that reduce the effect of the following component. The results support the assumption that positive and negative contrast are produced by symmetrical theoretical variables.
The experiment tested for stimulus specificity in extinguished operant responding. Eight pigeons ... more The experiment tested for stimulus specificity in extinguished operant responding. Eight pigeons pecked keys for food reinforcers delivered by a variable interval (VI) 60-s schedule. The key was illuminated with red light during some sessions and white light during others. Then, responding was placed on extinction. During some sessions of extinction, the color of the key light remained constant throughout the session (red or white). During other sessions the color changed at 30 min into the session (red to white or white to red). Response rate increased after the change of key color in extinction. If it is assumed that key color is part of the stimulus to which subjects habituate, then these results are consistent with McSweeney and Swindell's [J. Gen. Psychol. 129 (2002) 364] suggestion that responding declines in extinction partly because subjects habituate to the stimuli that support conditioned responding. Habituation is relatively specific to the exact nature of the stimulus presented. Therefore, changes in the stimulus violate stimulus specificity and restore habituated responding. The results are also consistent with other theories that attribute extinction to a reduction of stimulus control [e.g., Psychol. Bull. 114 (1993) 80; J. Exp. Psychol.: Anim. Behav. Process. 16 (1990) 235], but considerations such as parsimony and testability favor the habituation hypothesis over these theories.
The experiments tested the idea that changes in habituation to the reinforcer contribute to behav... more The experiments tested the idea that changes in habituation to the reinforcer contribute to behavioral interactions during multiple schedules. This idea predicts that changing an aspect of the reinforcer should disrupt habituation and produce an interaction. Pigeons and rats responded on multiple variable interval variable interval schedules. Introducing variability into the duration of reinforcers in one component increased response rates in both components when the schedules provided high, but not low, rates of reinforcement. The increases in constant-component response rates grew larger as the session progressed. Within-session decreases in responding were smaller when the other component provided variable-, rather than fixed-, duration reinforcers. These results are consistent with the idea that changes in habituation to the reinforcer contribute to behavioral interactions. They help to explain why interactions do not occur for some subjects under conditions that produce them for others. Finally, the results question the assumption that induction and behavioral contrast are always produced by different theoretical mechanisms.
McSweeney and Weatherly (1998) argued that differential habituation to the reinforcer contributes... more McSweeney and Weatherly (1998) argued that differential habituation to the reinforcer contributes to the behavioral interactions observed during multiple schedules. The present experiment confirmed that introducing dishabituators into one component of a multiple schedule increases response rate in the other, constant, component. During baseline, pigeons and rats responded on multiple variable interval 30-s variable interval 30-s schedules. During experimental conditions,
Rates of responding by rats were usually higher during the variable interval (VI) 30-s component ... more Rates of responding by rats were usually higher during the variable interval (VI) 30-s component of a multiple VI 30-s fixed interval (FI) 30-s schedule than during the same component of a multiple VI 30-s VI 30-s schedule (Experiment 1). Response rates were also usually higher during the FI 30-s component of a multiple VI 30-s FI 30-s schedule than during the same component of a multiple FI 30-s FI 30-s schedule (Experiment 2). The differences in response rates were not observed when the components provided VI or FI 120-s schedules. These results were predicted by the idea that differences in habituation to the reinforcer between multiple schedules contribute to behavioral interactions, such as behavioral contrast. However, differences in habituation were not apparent in the within-session patterns of responding. Finding differences in response rates in both experiments violates widely-held assumptions about behavioral interactions, including that behavioral contrast does not occur for rats and that improving the conditions of reinforcement decreases, rather than increases, response rate in the alternative component.
Experimental and Clinical Psychopharmacology, 2005
... Benjamin P. Kowal, Department of Psychology, Washington State University. ... For example, sa... more ... Benjamin P. Kowal, Department of Psychology, Washington State University. ... For example, satiety researchers are examining the contribution of sensitization and habituation to the cessation of eating (eg, Ernst & Epstein, 2002) and to human obesity (eg, Raynor & Epstein, 2001). ...
A considerable body of evidence indicates that consideration of the future and past are related. ... more A considerable body of evidence indicates that consideration of the future and past are related. Future discounting studies indicate that cigarette smokers discount future outcomes more than nonsmokers. The purpose of the present study was to determine if a similar profile of results could be obtained with a novel procedure evaluating the discounting of past outcomes, providing further support for future/past symmetry. Thirty cigarette smokers and twenty-nine nonsmokers participated in a computerized assessment of discounting of hypothetical future and past outcomes. Symmetry was supported, with a similar profile of results in future and past discounting procedures. These included: hyperbolic discounting, greater discounting of small-magnitude outcomes than large-magnitude outcomes, and greater discounting by cigarette smokers relative to nonsmokers.
Rats and pigeons responded on several concurrent schedules that provided different reinforcers in... more Rats and pigeons responded on several concurrent schedules that provided different reinforcers in the two components (food and water for rats, Experiment 1; wheat and mixed grain for pigeons, Experiment 2). The rate of responding and the time spent responding on each component usually changed within the session. The within-session changes in response rates and time spent responding usually followed different patterns for the two components of a concurrent schedule. For most subjects, the bias and sensitivity to reinforcement parameters of the generalized matching law, as well as the percentage of the variance accounted for, decreased within the session. Negative sensitivity parameters were sometimes found late in the session for the concurrent food-water schedules. These results imply that within-session changes in responding could cause problems for assessing the validity of quantitative theories of concurrent-schedule responding when the components provide different reinforcers. They question changes in a general motivational state, such as arousal, as a complete explanation for within-session changes in responding. The results are compatible with satiation for, or sensitization-habituation to, the reinforcers as explanations.
Within-session decreases in operant responding as a function of pre-session feedings. by Eric S. ... more Within-session decreases in operant responding as a function of pre-session feedings. by Eric S. Murphy , Frances K. McSweeney , Benjamin P. Kowal During the past decade, the phenomenon of within-session changes in operant responding has receive.
The current research attempted to decrease individuals' rates of delay discounting by introducing... more The current research attempted to decrease individuals' rates of delay discounting by introducing decoys that are similar but inferior to delayed rewards. Two experiments in the current study compared patterns of delay discounting generated by repeated choices between two hypothetical monetary rewards in the absence or presence of a decoy. Binary questionnaires (i.e., decoy absent) included questions with two options: a smaller-sooner (SS) reward and a larger-later (LL) reward. Trinary questionnaires (i.e., decoy present) included questions with three options: an SS reward, an LL reward, and a decoy. If an option is at least as rewarding on every dimension of value as an alternative and the option is more rewarding than an alternative on at least one dimension, then the option is considered to dominate the alternative (Wedell, 1991). The first experiment assessed the influence of decoys dominated by LL rewards (LL − decoys), which were constructed to be similar (on the dimension of amount) but inferior (on the dimension of delay) to LL rewards. The second experiment examined the effects of counterbalancing the order of binary and trinary questionnaires. In the first experiment, participants discounted to a lesser degree when LL − decoys were present as compared to when they were absent. In the second experiment, participants only discounted to a lesser degree on trinary questionnaires with LL − decoys when they had not previously completed binary questionnaires. Patterns of discounting generated by binary questionnaires were similar to those generated by trinary questionnaires when decoys are present; however, the degree to which individuals discounted delayed rewards was affected by the number of and type of options that were available. The current results join previous evidence suggesting that rates of delay discounting are sensitive to a variety of contextual influences.
One of the hallmarks of drug addiction is a limitation of the temporal horizon of events that aff... more One of the hallmarks of drug addiction is a limitation of the temporal horizon of events that affect the behavior of drug users. The purpose of this experiment was to examine the time period over which smoking was influenced by an earlier opportunity to smoke. Baseline sessions measured how much was smoked in a current opportunity when it was preceded by a two-hour wait time in which no smoking was allowed. Following the baseline phase, we examined the effects of temporal distance when an earlier opportunity to smoke (upon completion of a FR100) preceded current smoking (upon completion of a PR). Temporal distance between these two opportunities to smoke was varied from 0 min to 120 min. We found that current smoking for the group was reduced from baseline levels when the temporal distance was 0 min. At temporal distances ranging from 30 min to 90 min, the individual's smoking returned to levels that were similar to baseline. Breakpoints were also a function of previous smoking, and latencies to first puff of the session followed a similar trend. These findings provide evidence of the limited temporal horizons related to smoking bouts of smokers and may provide a useful measure for metabolism differences across populations. In addition, we suggest that the quantitative description of satiety provided by our procedures may validate drug replacement therapies involved in cessation treatments.
Experimental and Clinical Psychopharmacology, 2005
The authors argue that drug taking is an operant behavior that is reinforced by the drug itself. ... more The authors argue that drug taking is an operant behavior that is reinforced by the drug itself. The effectiveness of a drug as a reinforcer is modulated by sensitization and habituation to the drug as it is consumed. According to this model, drug taking stops when habituation reduces the ability of the drug to reinforce its own consumption. Drug taking resumes when spontaneous recovery restores the effectiveness of the drug as a reinforcer. This parsimonious model provides a framework for understanding many findings in the drug literature, including acute and chronic tolerance, the effect of deprivation on consumption, the contextual specificity of tolerance, polydrug abuse, cross-sensitization between stress and drugs, behavioral sensitization, priming, and reinstatement. Although this model cannot explain all aspects of drug taking (e.g., the effect of cognitive manipulations), it has many implications for understanding and controlling human drug consumption and addiction.
Two algorithms are commonly applied in computerized temporal discounting procedures (Decreasing A... more Two algorithms are commonly applied in computerized temporal discounting procedures (Decreasing Adjustment and Double-Limit Algorithms); however, the degree to which the two algorithms produce similar patterns of discounting is unknown. The present experiment compared the two common algorithms across sign (gains and losses) and magnitude ($10 and $1000) conditions. Twenty participants made choices between larger later and smaller sooner alternatives that were presented by each of the algorithms in separate conditions. Strong correlations were found between the two measures; however, the Decreasing Adjustment Algorithm tended to produce lower indifference points and higher rates of discounting than the Double-Limit Algorithm. Both algorithms found significant magnitude effects. Less consistent results were found when comparing the two algorithms across sign. The present results suggest that researchers should apply caution when making comparisons between outcomes of delay discounting studies that have used the two different algorithms. However, the interpretation of findings from individual studies is probably not strongly affected by the use of different computer algorithms.
The seemingly irrational behavior exhibited by individuals with addiction may be understood by co... more The seemingly irrational behavior exhibited by individuals with addiction may be understood by considering their temporal horizon. In this paper, we reviewed published literature and current research concerning how delay discounting, a measure of temporal horizon, has been employed to understand addiction. Specifically, studies of delay discounting among addicted individuals and other psychiatric populations, current controversies in the delay discounting literature, and new developments were reviewed. Addicted individuals discount the long-term consequences of their behavior at a higher rate than matched controls. Current controversies illustrate the need for continued research. Given the rising interest in using delay discounting to understand addictive behaviors, in terms of both overt behavior and at the level of brain activity, we believe research in this field will continue to produce substantial progress for the next several years.
Nineteen nicotine-deprived cigarette smokers received monetary rewards for each minute they choos... more Nineteen nicotine-deprived cigarette smokers received monetary rewards for each minute they choose not to initiate smoking in 2-hour laboratory sessions followed by a 30-min period of enforced abstinence from smoking. Reinforcer amounts were delivered according to one of three schedules: increasing, decreasing, and constant. Relapse time (time until first smoke) was shortest in the decreasing condition, longest in the increasing condition, and intermediate in the constant condition. All differences were significant except in the constant-decreasing comparison. The relationships between a battery of baseline assessments and relapse times were examined. Relapse times were predicted by delay-discounting coefficients (k) for $10 and $1000 in money, and for $1000 of cigarettes. Relapse times were also predicted by the number of cigarettes smoked daily and a Wisconsin Card Sorting Test score. Performance on the Stroop Task and the Fagerström Test for Nicotine Dependence differentiated participants dichotomized into those who relapsed "earlier" in sessions versus those who first smoked "later." Variability on some scores from smoking-urges and affect questionnaires administered after smoking-room sessions was explained by measures related to in-session nicotine intake. Results are discussed as they relate to contingency-management procedures, predictors of relapse, and the competing neuro-behavioral decision systems theory of addiction.
We review behavioral-and neuroeconomic research that identifies temporal discounting as an import... more We review behavioral-and neuroeconomic research that identifies temporal discounting as an important component in the development and maintenance of drug addiction. First we review behavioral economic research that explains and documents the contribution of temporal discounting to addiction. This is followed with recent insights from neuroeconomics that may provide an explanation of why drug dependent individuals discount the future. Specifically, neuroeconomics has identified two competing neural systems that are related to temporal discounting using brainimaging techniques that examine the relative activation of different brain regions for temporal discounting. According to the competing neural systems account, choices for delayed outcomes are related to the prefrontal cortex (i.e., the "executive system") and choices for immediate outcomes are related to the limbic brain regions (i.e., the "impulsive system"). Temporal discounting provides a useful framework for future imaging research, and suggests a novel approach to designing effective drug dependence prevention and treatment programs.
The present experiment examined whether habituation contributes to within-session decreases in op... more The present experiment examined whether habituation contributes to within-session decreases in operant responding for water reinforcers. The experiment asked if this responding can be dishabituated, a fundamental property of habituated behavior. During baseline, rats' lever pressing was reinforced by water on a variable interval 15-s schedule. During experimental conditions, rats responded on the same schedule and a new stimulus was introduced for 5 min at 15, 30 or 45 min into the 60-min session. The new stimulus was extinction, continuous reinforcement or flashing lights in different conditions. Rate of responding primarily decreased within the session during baseline. Introducing a new stimulus sometimes suppressed (extinction, continuous reinforcement) and sometimes increased (flashing lights) responding while it was in effect. The new stimulus increased responding after it ended and before it was presented in the session. The results are incompatible with the idea that non-habituation satiety factors (e.g., cellular hydration and blood volume) contributed to within-session changes in responding. These satiety factors should increase with increases in consumption, decrease with decreases in consumption and remain constant with constant consumption of water. Nevertheless, all stimulus changes increased operant responding for water. These results support the idea that habituation contributes to within-session decreases in responding for water reinforcers.
Experimental and Clinical Psychopharmacology, 2006
This study examined whether habituation, a decrease in responsiveness to a repeatedly presented s... more This study examined whether habituation, a decrease in responsiveness to a repeatedly presented stimulus, occurs to ethanol reinforcers in alcohol-preferring (P) rats. Three fundamental properties of habituation were evaluated: generality, spontaneous recovery, and dishabituation. In each experiment, P rats' lever pressing was reinforced by 10% ethanol on a variable-interval 15-s schedule during 50-min sessions. Experiment 1 evaluated the generality of habituation to repeatedly presented stimuli by using ethanol and water reinforcers. Rates of responding were higher for ethanol than they were for water. Additionally, the within-session patterns of responding differed for each reinforcer, suggesting that the pattern of responding was specific to the exact nature of the repeatedly presented reinforcer. Experiment 2 examined spontaneous recovery, an increase in responsiveness to a habituated stimulus when that stimulus is not presented for a time, by separating experimental sessions by 5 min, 2 hr, or 24 hr. Early-session rates of responding during Session 2 were slower than the corresponding rates during Session 1 when sessions were separated by 5 min or 2 hr. Response rates and within-session patterns of responding during Sessions 1 and 2 were similar when sessions were separated by 24 hr. Experiment 3 tested for dishabituation, a restoration of responsiveness following the presentation of an extraneous stimulus, by presenting a tone or a light 24 min and 55 s into the session. Rates of responding temporarily increased after the tone was presented. The results of these experiments support the idea that habituation contributes to the regulation of ethanol consumption.
Pigeons’ keypecking was reinforced by food on baseline schedules of multiple variable interval (V... more Pigeons’ keypecking was reinforced by food on baseline schedules of multiple variable interval (VI)x VIx and on contrast schedules of multiple VIx VIy. Deprivation of food was varied by maintaining subjects at 75%, 85%, and 95% (±2%) of their free-feeding weights. Positive and negative behavioral contrast were observed. The size of the contrast was not systematically altered by changes in deprivation. Positive and negative contrast were both larger later in the session than they were earlier. Withinsession decreases in responding were steeper for the baseline than for the contrast schedules for positive contrast. Within-session decreases were steeper for the contrast than for the baseline schedules for negative contrast. These results were predicted by the idea that different amounts of habituation to the reinforcer during the baseline and contrast schedules contribute to behavioral contrast. The results show that contrast occurs under conditions that reduce the effect of the following component. The results support the assumption that positive and negative contrast are produced by symmetrical theoretical variables.
The experiment tested for stimulus specificity in extinguished operant responding. Eight pigeons ... more The experiment tested for stimulus specificity in extinguished operant responding. Eight pigeons pecked keys for food reinforcers delivered by a variable interval (VI) 60-s schedule. The key was illuminated with red light during some sessions and white light during others. Then, responding was placed on extinction. During some sessions of extinction, the color of the key light remained constant throughout the session (red or white). During other sessions the color changed at 30 min into the session (red to white or white to red). Response rate increased after the change of key color in extinction. If it is assumed that key color is part of the stimulus to which subjects habituate, then these results are consistent with McSweeney and Swindell's [J. Gen. Psychol. 129 (2002) 364] suggestion that responding declines in extinction partly because subjects habituate to the stimuli that support conditioned responding. Habituation is relatively specific to the exact nature of the stimulus presented. Therefore, changes in the stimulus violate stimulus specificity and restore habituated responding. The results are also consistent with other theories that attribute extinction to a reduction of stimulus control [e.g., Psychol. Bull. 114 (1993) 80; J. Exp. Psychol.: Anim. Behav. Process. 16 (1990) 235], but considerations such as parsimony and testability favor the habituation hypothesis over these theories.
The experiments tested the idea that changes in habituation to the reinforcer contribute to behav... more The experiments tested the idea that changes in habituation to the reinforcer contribute to behavioral interactions during multiple schedules. This idea predicts that changing an aspect of the reinforcer should disrupt habituation and produce an interaction. Pigeons and rats responded on multiple variable interval variable interval schedules. Introducing variability into the duration of reinforcers in one component increased response rates in both components when the schedules provided high, but not low, rates of reinforcement. The increases in constant-component response rates grew larger as the session progressed. Within-session decreases in responding were smaller when the other component provided variable-, rather than fixed-, duration reinforcers. These results are consistent with the idea that changes in habituation to the reinforcer contribute to behavioral interactions. They help to explain why interactions do not occur for some subjects under conditions that produce them for others. Finally, the results question the assumption that induction and behavioral contrast are always produced by different theoretical mechanisms.
McSweeney and Weatherly (1998) argued that differential habituation to the reinforcer contributes... more McSweeney and Weatherly (1998) argued that differential habituation to the reinforcer contributes to the behavioral interactions observed during multiple schedules. The present experiment confirmed that introducing dishabituators into one component of a multiple schedule increases response rate in the other, constant, component. During baseline, pigeons and rats responded on multiple variable interval 30-s variable interval 30-s schedules. During experimental conditions,
Rates of responding by rats were usually higher during the variable interval (VI) 30-s component ... more Rates of responding by rats were usually higher during the variable interval (VI) 30-s component of a multiple VI 30-s fixed interval (FI) 30-s schedule than during the same component of a multiple VI 30-s VI 30-s schedule (Experiment 1). Response rates were also usually higher during the FI 30-s component of a multiple VI 30-s FI 30-s schedule than during the same component of a multiple FI 30-s FI 30-s schedule (Experiment 2). The differences in response rates were not observed when the components provided VI or FI 120-s schedules. These results were predicted by the idea that differences in habituation to the reinforcer between multiple schedules contribute to behavioral interactions, such as behavioral contrast. However, differences in habituation were not apparent in the within-session patterns of responding. Finding differences in response rates in both experiments violates widely-held assumptions about behavioral interactions, including that behavioral contrast does not occur for rats and that improving the conditions of reinforcement decreases, rather than increases, response rate in the alternative component.
Experimental and Clinical Psychopharmacology, 2005
... Benjamin P. Kowal, Department of Psychology, Washington State University. ... For example, sa... more ... Benjamin P. Kowal, Department of Psychology, Washington State University. ... For example, satiety researchers are examining the contribution of sensitization and habituation to the cessation of eating (eg, Ernst & Epstein, 2002) and to human obesity (eg, Raynor & Epstein, 2001). ...
A considerable body of evidence indicates that consideration of the future and past are related. ... more A considerable body of evidence indicates that consideration of the future and past are related. Future discounting studies indicate that cigarette smokers discount future outcomes more than nonsmokers. The purpose of the present study was to determine if a similar profile of results could be obtained with a novel procedure evaluating the discounting of past outcomes, providing further support for future/past symmetry. Thirty cigarette smokers and twenty-nine nonsmokers participated in a computerized assessment of discounting of hypothetical future and past outcomes. Symmetry was supported, with a similar profile of results in future and past discounting procedures. These included: hyperbolic discounting, greater discounting of small-magnitude outcomes than large-magnitude outcomes, and greater discounting by cigarette smokers relative to nonsmokers.
Rats and pigeons responded on several concurrent schedules that provided different reinforcers in... more Rats and pigeons responded on several concurrent schedules that provided different reinforcers in the two components (food and water for rats, Experiment 1; wheat and mixed grain for pigeons, Experiment 2). The rate of responding and the time spent responding on each component usually changed within the session. The within-session changes in response rates and time spent responding usually followed different patterns for the two components of a concurrent schedule. For most subjects, the bias and sensitivity to reinforcement parameters of the generalized matching law, as well as the percentage of the variance accounted for, decreased within the session. Negative sensitivity parameters were sometimes found late in the session for the concurrent food-water schedules. These results imply that within-session changes in responding could cause problems for assessing the validity of quantitative theories of concurrent-schedule responding when the components provide different reinforcers. They question changes in a general motivational state, such as arousal, as a complete explanation for within-session changes in responding. The results are compatible with satiation for, or sensitization-habituation to, the reinforcers as explanations.
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Papers by Benjamin Kowal