Frances K Mcsweeney

• PhD, Harvard University
• Professor at Washington State University

Dr. McSweeney is Regents Professor of Psychology and Vice Provost for Faculty Affairs at Washington State University (WSU). She received her B. A., Summa Cum Laude, from Smith College and her Masters and Ph.D. from Harvard University. She taught for one year at McMaster University before joining the faculty at WSU where she rose through the ranks t...

Response rates may increase, decrease, or increase and then decrease within conditioning sessions even when the distribution of reinforcers or unconditioned stimulus (US) does not vary across the session. This chapter reviews the empirical characteristics of within-session changes in operant responding and then considers potential theoretical expla...

Two experiments investigated the role of generalization in the acquisition of autoshaped keypecking. In Experiment 1, 20 pigeons were exposed to an autoshaping procedure in the presence or absence of food magazine illumination. Pigeons did not peck a lighted response key when the food magazine was not illuminated, but they did reliably peck the key...

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...

We examined participation by women in four journals devoted to organizational behavior management from 1978 to 2000. The percentage of articles with at least one female author, female authors, female first authors, editorial board members, and associate editors generally increased for all four journals. Increases in female first authors were partic...

We argue that sensitization and habituation occur to the sensory properties of reinforcers when those reinforcers are presented repeatedly or for a prolonged time. Sensitization increases, and habituation decreases, the ability of a reinforcer to control behavior. Supporting this argument, the rate of operant responding changes systematically withi...

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% eth...

Classical and operant conditioning are procedures for changing behavior. Behavior changes when a previously neutral stimulus predicts an important stimulus (classical conditioning). Behavior also changes when a response produces a particular consequence (operant conditioning).

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 dis-habituated, a fundamental property of habituated behavior. During baseline, rats' lever pressing was reinforced by water on a variable interval 15-s schedule. Dur...

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 t...

The authors thank M. N. Branch (2005), J. K. Rowlett (2005), and S. Siegel (2005) for their comments. Branch's commentary contains many misconceptions. The authors try to clarify these issues. They agree with Rowlett that converging approaches to understanding drug consumption will ultimately yield the best results. The authors also agree that meas...

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, pi...

Reinforcers lose their effectiveness when they are presented repeatedly. Early researchers labeled this loss of effectiveness as satiation without conducting an experimental analysis. When such an analysis is conducted, habituation provides a more precise and empirically accurate label for the changes in reinforcer effectiveness. This paper reviews...

Pigeons' keypecking was reinforced by food on baseline schedules of multiple variable interval (VI) x VI x and on contrast schedules of multiple VI x VI y. 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 contr...

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. Intro...

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 extinctio...

In the present experiment, the authors investigated the idea that within-session changes in operant response rates occur because subjects sensitize and then habituate to the reinforcer. If that is true, then altering an aspect of the reinforcer within the session should alter the observed within-session responding. The authors tested that idea by h...

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 ne...

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 tha...

Pigeons pecked keys on concurrent-chains schedules that provided a variable interval 30-sec schedule in the initial link. One terminal link provided reinforcers in a fixed manner; the other provided reinforcers in a variable manner with the same arithmetic mean as the fixed alternative. In Experiment 1, the terminal links provided fixed and variabl...

The effect of supplemental feedings on pigeons' within-session changes in operant key-pecking was investigated. In different conditions, the feeding was either Purina Pigeon Checkers or mixed grain. The feedings were delivered 1,4, and 12 hr prior to an experimental session. Responding changed significantly and systematically within sessions for al...

Reinforcers lose their effectiveness when they are presented repeatedly. Traditionally, this loss of effectiveness has been labeled satiation. However, recent evidence suggests that habituation provides a more accurate and useful description. The characteristics of behavior undergoing satiation differ for different stimuli (e.g., food, water), and...

McSweeney and Weatherly (1998) suggested that multiple-schedule behavioral contrast may be explained, at least partly, bydifferences in the amount of habituation to the reinforcer produced during the baseline and contrast phases of a contrast experiment.The present experiment studied behavioral contrast when pigeons pecked keys for food reinforcers...

Psychologists routinely attribute the characteristics of conditioned behavior to complicated cognitive processes. For example, many of the characteristics of behavior undergoing extinction have been attributed to retrieval from memory. The authors argue that these characteristics may result from the simpler process of habituation. In particular, co...

We examined participation by women in journals devoted to social, developmental, cognitive, and general psychology. Authorship and first authorship by women increased from 1978 to 1997 for most journals. Participation by women on the editorial staff did not keep pace with their increased authorship for social and developmental psychology. Based on...

Three experiments tested the hypothesis that habituation contributes to the regulation of wheel running. Rats ran in a wheel for 30-min sessions. Experiment 1 demonstrated spontaneous recovery. Rats ran more and the within-session decreases in running were smaller after 2 days of wheel deprivation than after 1 day. Experiment 2 demonstrated dishabi...

Rats (Experiment 1) and pigeons (Experiment 2) responded on several concurrent variable interval (VI) variable ratio (VR) schedules. The rate of, but not the time spent, responding in each component usually changed within-sessions. The bias and sensitivity parameters of the generalized matching law (GML) did not change systematically within-session...

The idea that similar selective processes operate in gene-based evolution, immunology, and operant psychology provides an intuitively appealing metaphor. This idea also isolates questions that operant psychologists should ask and makes some empirical predictions. However, the idea currently lacks the detail needed to precisely separate it from some...

Odum (2000) criticized our recent conclusions about the participation of women in the experimental analysis of behavior (McSweeney & Swindell, 1998). We address her criticisms here. We argue against the need for statistical tests. We show that our conclusions still apply to all journals except the Journal of the Experimental Analysis of Behavior ev...

Two experiments tested the hypothesis that habituation contributes to within-session decreases in responding. In Experiment 1, rats’ leverpressing was reinforced under a fixed ratio (FR) 4 schedule throughout the baseline sessions. During the dishabituation sessions, the first 21 min and the last 21 min were FR 4; dishabituating events occurred dur...

The effectiveness of a reinforcer in maintaining behavior (its value) changes systematically with successive deliveries of that reinforcer. Some misconceptions have impeded our understanding of these changes. The misconceptions include the idea that the changes never occur or occur only when large reinforcers are used; that they always occur; that...

The authors of four papers recently reported that satiation provides a better explanation than habituation for within-session decreases in conditioned responding. Several arguments question this conclusion. First, the contribution of habituation to within-session changes in responding seems clearly established. Information that is consistent with h...

The status of women in applied behavior analysis was examined by comparing the participation of women in the Journal of Applied Behavior Analysis (JABA) to their participation in three similar journals. For all journals, the percentage of articles with at least one female author, the percentage of authors who are female, and the percentage of artic...

Pigeons and rats responded on fixed-ratio schedules with requirements ranging from 5 to 120 responses. Consistent with past results from several schedules and procedures, responding usually changed systematically within experimental sessions. The within-session changes were usually larger and were less symmetrical around the middle of the session f...

An assumption inherent in the theory and practice of operant psychology is that response rate is relatively invariant during steady-state procedures. Recent research has refuted this assumption, demonstrating instead that response rate changes in a large and systematic fashion during many steady-state operant procedures. This finding mandates that...

Pigeons (Experiment 1) and rats (Experiment 2) responded on variable interval (VI), variable time (VT), and extinction procedures. All three procedures were conducted for three different baseline rates of reinforcement. When the rates of reinforcement obtained from the VI and VT schedules did not differ significantly, the within-session patterns of...

The authors propose that the goal objects of motivated behaviors serve as reinforces. Animals sensitize and then habituate to these reinforcers with repeated contact, altering their ability to control behavior. Several characteristics of motivation are consistent with this idea. Motivated behaviors decrease in strength with contact with the goal (h...

Rats (Experiment 1) and pigeons (Experiment 2) responded on several concurrent fixed interval variable interval schedules. The programmed rate of reinforcement varied from 15 to 240 reinforcers per hour across conditions for each component. The rate of, but not the time spent, responding on each component usually changed within sessions. The patter...

The study investigates the idea that within-session changes in responding are produced by arousal and satiation. General activity, measured by the displacement of floor panels, was used as an index of these variables. In Experiment 1, pigeons pecked a key on a simple variable-interval schedule and general activity was also recorded. In Experiment 2...

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 ope...

We examined the status of women in the experimental analysis of behavior by comparing authorship by women in the Journal of the Experimental Analysis of Behavior (JEAB) to authorship by women in three similar journals. For all journals, the percentage of articles with at least one female author, the percentage of authors who are female, and the per...

Rats and pigeons responded on multiple variable interval 30-s variable interval 30-s and multiple variable interval 60-s variable interval 60-s schedules. The 60-min sessions began 0, 5, 10, 15 or 30 min after the subject was placed in the experimental enclosure, determined randomly. Early-session response rates were usually higher, and the early-s...

Rats pressed levers for sweetened condensed milk reinforcers delivered according to a multiple variable-interval 1-min, variable-interval 1-min schedule during 60-min baseline sessions. The obtained pattern of responding was an early-session increase in responding followed by a relatively constant rate of responding during the remainder of the sess...

Habituation to the reinforcer may contribute to multiple-schedule behavioral contrast. According to this argument, reducing reinforcers in one component of a multiple schedule reduces habituation to the reinforcer. Reducing habituation enhances the value, or effectiveness, of the remaining reinforcers, producing positive contrast. Enriching the rei...

Rats and pigeons responded on multiple variable interval 30-s variable interval 30-s and multiple variable interval 60-s variable interval 60-s schedules. The 60-min sessions began 0, 5, 10, 15 or 30 min after the subject was placed in the experimental enclosure, determined randomly. Early-session response rates were usually higher, and the early-s...

The present study was an attempt to determine the factors to which subjects sensitize and/or habituate within experimental sessions. Rats pressed a lever and pigeons pecked a key for food reinforcers delivered during a 60 min session. In experiment 1, subjects initially responded on a simple variable-interval 30 s schedule that consisted of 25 inte...

Recent research has demonstrated that rate of responding frequently changes in a robust and systematic manner during experimental sessions in which organisms engage in operant responding. One potential cause for these changes in response rate is that levels of exploration change during experimental sessions and that high levels of exploration inter...

Rats pressed levers for food delivered by several fixed interval schedules. A drinking spout or running wheel was also available during some conditions, but not during others. The rate of lever pressing, drinking and running often changed within experimental sessions. The within-session patterns of lever pressing did not differ when drinking or run...

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 respon...

Operant responding often changes within sessions, even when factors such as rate of reinforcement remain constant. The present study was designed to determine whether within-session response patterns are determined by the total number of reinforcers delivered during the session or only by the reinforcers earned by the operant response. Four rats pr...

Large and systematic changes in response rates often occur within sessions during operant conditioning procedures. In the present experiment, we asked whether the value of the reinforcer that supports responding also changes within sessions. Pigeons pecked a key for mixed grain available throughout the session. Occasionally, wheat was also provided...

Two experiments examined within-session changes in responding during discrimination procedures. In Experiment 1, rate of responding changed significantly within sessions during symbolic delayed matching-to-sample tasks when the delay between the stimulus and the choice period was short (1–5 sec), but not when it was long (8–12 sec). The percentage...

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...

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...

Two experiments examined within-session changes in operant responding when cocaine or cocaine plus food served as the reinforcer. In Experiment 1, male rats self-administered intravenous cocaine according to several fixed interval schedules. The within-session patterns of responding differed for the different schedules early in the session, but the...

Four pigeons were exposed to autoshaping procedures in which an 8-second light on a response key was followed by food. Pecks on the key had no scheduled consequences. Subjects were also exposed to negative automaintenance procedures in which a peck on the illuminated key canceled the fol- lowing food. The intertrial interval varied from an average...

Five rats and 4 pigeons responded for food delivered by several concurrent variable-interval schedules. The sum of the rates of reinforcement programmed for the two components varied from 15 to 480 reinforcers per hour in different conditions. Rates of responding usually changed within the experimental session in a similar manner for the two compon...

The influence of solid-liquid demixing, liquid-liquid demixing and vitrification on the morphology of polylactide membranes has been investigated. To study the effects of crystallization of polylactides on the membrane and morphology, polylactides of varying stereoregularity were used. The polymers applied were poly-l-lactide (PLLA) and copolymers...

Four rats and four pigeons responded for food delivered by variable interval schedules that provided programmed rates of reinforcement ranging from 15 to 480 reinforcers per hour. Rate of responding increased, decreased, or increased and then decreased within sessions. The within-session pattern of responding changed with changes in the programmed...

Two experiments were conducted during which undergraduates responded during a variable-interval (VI) 60-second operant task. The first experiment consisted of either three 60-minute sessions or three 30-minute sessions. During Experiment 1 subjects were informed as to the length of the session and the number of sessions that would be conducted. Dur...

Behavioral contrast can be defined as an inverse relation between responding in one component of a multiple schedule and the conditions of reinforcement in the other component. The present study attempted to determine whether adult humans would display behavioral contrast. It also attempted to determine whether adult humans and pigeons would displa...

Operant responding may change systematically within experimental sessions even when the contingencies of reinforcement remain constant across the session. In two experiments, eight pigeons pecked a key for mixed grain delivered by variable interval or multiple variable interval schedules. Experiment 1 showed that changes in the rate at which reinfo...

Eight pigeons and 10 rats responded on variable interval 1-min or variable interval 30-s schedules. During baseline, the same operandum produced reinforcers throughout the session. During the switch conditions, performing one response produced reinforcers early in the session and performing a different response produced reinforcers later. The switc...

Three pigeons pecked keys and 5 rats pressed levers for food delivered on variable-interval schedules. During baseline conditions, subjects responded on a variable-interval 40-s schedule throughout the session. During experimental conditions, the programmed rate of reinforcement changed every 10 min in the 50-min sessions. When rats served as subje...

Five rats responded on several concurrent schedules in which pressing a key produced reinforcers in one component and pressing a lever produced reinforcers in the other component (Experiment 1). Four pigeons responded on several concurrent keypeck treadlepress schedules (Experiment 2). The programmed rates of reinforcement varied from 15 to 240 rei...

Three pigeons responded on variable interval 60-second and variable interval 30-second schedules. The duration of access to mixed grain was varied from 2-to 20-seconds per reinforcer in different conditions. Within-session patterns of responding did not differ when subjects received 2- versus 20-seconds access to the reinforcer for the schedule pro...

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 cal...

Rats pressed keys or levers for water reinforcers delivered by several multiple variable-interval schedules. The programmed rate of reinforcement varied from 15 to 240 reinforcers per hour in different conditions. Responding usually increased and then decreased within experimental sessions. As for food reinforcers, the within-session changes in bot...

Rats pressed levers for water reinforcers delivered by multiple variable interval one-minute variable interval one-minute schedules. Experiment 1 manipulated the stimuli signalling the components of the multiple schedule. Experiment 2 varied the experimental environment. Responding changed significantly within the session during every condition of...

Five rats pressed levers for food delivered by a multiple variable interval 1-min variable interval 1-min schedule. In theunpredictable conditions, sessions were 20, 40, 60, 80, or 100 min long, determined randomly at the beginning of each session. In thepredictable conditions, each of these session durations was presented for 15 consecutive sessio...

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 ap...

Pigeons' key pecking was reinforced by food delivered by several fixed-interval, variable-ratio, and differential-reinforcement-of-low-rate schedules. Rate of responding, number of responses per reinforcer, length of postreinforcement pause, running response rate, and the time required to collect an available reinforcer changed systematically withi...

Four pigeons pecked keys for food reinforcers delivered by variable interval I-min schedules during two successive SO-min sessions or one IOO-min session. When 50-min sessions were conducted, they were separated by a 0-, IO- or 30-min delay, spent either inside or outside of the experimental enclosure. Responding usually increased to a peak and the...

When the procedure is held constant within an experimental session, responding often changes systematically within that session. Many of these within-session changes in responding cannot be dismissed as learning curves or by-products of satiation. They have been observed in studies of positive reinforcement, avoidance, punishment, extinction, discr...

Pigeons pecked keys for food reinforcers delivered by multiple variable-interval 2-min variable-interval 2-min schedules. Positive behavioral contrast was created by changing one component to extinction; negative contrast was achieved by changing one component to a variable-interval 15-s schedule. The duration of each component was varied independe...

Rates of responding changed systematically across sessions for rats pressing levers and keys and for pigeons pressing treadles and pecking keys. A bitonic function in which response rates increased and then decreased across sessions was the most common finding, although an increase in responding also occurred alone. The change in response rate was...

Rats pressed keys for sweetened condensed milk delivered by multiple schedules. Component duration varied from five seconds to 16 minutes. Positive contrast did not occur for any duration. That is, the rate of responding emitted during a variable interval component of a multiple schedule was not greater when the other component was extinction than...

Rats pressed levers for Noyes pellets or keys for sweetened condensed milk reinforcers delivered by multiple schedules. Session length and baseline rates of reinforcement were varied in two experiments. Rates of responding increased during the early part of the session and then decreased for both responses and reinforcers, as well as for all subjec...

Three pigeons pecked keys for food reinforcers delivered by multiple variable interval variable interval schedules in the first part of each session (baseline) and by multiple variable interval extinction schedules in the second part of each session (contrast). The variable interval schedules delivered reinforcers after an average of 4 min or 30 se...

Ten rats pressed levers for food reinforcers delivered by multiple schedules. Behavioral contrast was measured using a within-session procedure that presented the baseline and contrast schedules within single sessions. The absolute sizes of both positive and negative contrast increased and then decreased as components lengthened. Negative induction...

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 de...

The effects of reinforcement rate on behavioral contrast were examined in pigeons and rats. Each species was exposed to a series of 12 multiple variable-interval schedules, divided into four 3-schedule series. Each series consisted of a standard contrast manipulation, and baseline schedules provided a different rate of reinforcement in each of the...

The present study examined behavioral contrast during concurrent and multiple schedules that provided food and alcohol reinforcers. Concurrent-schedule contrast occurred in the responding reinforced by food when alcohol reinforcers were removed. It also occurred in the responding reinforced by alcohol when food was removed. Multiple-schedule contra...

Pigeons pecked keys for food reinforcers delivered by multiple schedules. Three experiments examined changes in the size of positive contrast with changes in component duration. They used a within-session procedure which measured rates of responding during the baseline and contrast phases within the same session. Contrast was largest for shorter co...

The present paper argues that multiple-schedule behavioral contrast occurs because delayed reinforces suppress behavior. According to this idea, some reinforcers delivered in the second component of a multiple schedule suppress responding during the first component because they follow that responding after a delay. Removing second-component reinfor...

Behavioral contrast was studied during multiple schedules which provided qualitatively different reinforcers in the two components. Five rats responded on a baseline schedule in which both components delivered food reinforcers (food-food), and then on a contrast schedule in which one component delivered food and the other delivered water (food-wate...

Pigeons pecked keys or pressed treadles on variable ratio schedules in which they earned their total daily ration of food. Ratio requirements varied in five steps from 15 to 240 responses per reinforcer. Results were generally similar for pecking and pressing. Rates of responding increased with increases in the ratio requirement, but decreased with...

Positive and negative behavioral contrast were examined when pigeons were required to keypeck in one component and treadle press in the other component of a series of multiple schedules. The experimental conditions were constructed so that the positive and negative contrast groups were exposed to complementary conditions. Positive keypeck and negat...

Three experiments examined the effects of opportunities for an alternative response (drinking) on positive behavioral contrast of rats' food-reinforced bar pressing. In both Experiments 1 and 2 the baseline multiple variable-interval schedules were rich (variable interval 10-s), and contrast was examined both with and without a water bottle present...

Pigeons' rates of responding on simple schedules appearing alone or as components of signal-key multiple schedules were not systematically different early in training, but were different later in training. This suggests that a simple schedule may be an appropriate baseline from which to measure behavioral contrast. Positive behavioral contrast, lik...

Three experiments examined changes in size of multiple-schedule behavioral contrast with changes in an independent variable. Experiment 1 found that positive contrast generally increased with increases in component duration when pigeons pressed treadles. Experiments 2 and 3 found that positive and negative contrast generally increased with increase...

Positive behavioral contrast has been observed when pigeons press treadles on multiple schedules for high rates of reinforcement, but not for low rates. Negative treadle-press contrast has been observed for low rates of reinforcement. Two experiments showed that differences between response rates emitted during simple and multiple schedules appear...

The literature was examined to determine how well the generalized matching law (Baum, 1974) describes multiple-schedule responding. In general, it describes the data well, accounting for a median of 91% of the variance. The median size of the undermatching parameter was 0.46; the median bias parameter was 1.00. The size of the undermatching paramet...

Two experiments examined the effects of baseline reinforcement rate and component duration on behavioral contrast and on re-allocation of interim behavior in rats. Positive behavioral contrast occurred during multiple variable-interval 10-second extinction (VI 10 EXT) after a multiple VI 10 VI 10 baseline condition, but not during multiple VI 60 EX...

This study examined a conservation model (Allison & Mack, 1982) that predicts a linear relation between the weighted sum of two responses, autoshaped leverpressing and polydipsia, and the amount of food delivered on a variable-time schedule. Fifteen rats were assigned randomly to one of three groups. The rats in Group 1 were maintained at 80% of th...

In a test of Herrnstein's (1970, 1974) equation for simple schedules, 15 pigeons pecked a key that produced food delivered according to variable-interval schedules. One group of birds was water deprived, and food-reinforced key pecking occurred in the presence of free water. Two other groups were not water deprived; water was present for one and ab...