Partial Reinforcement Schedule Research Articles

Delaying extinction weakens the partial reinforcement extinction effect.

Conditioned responding that has been extinguished can spontaneously return when the conditioned stimulus (CS) is first presented after an extended delay. This spontaneous recovery of responding suggests that the memory of nonreinforced experience with the CS is impaired over the delay period. Rescorla (2007) provided evidence that this effect of time on nonreinforcement is not specific to extinction. He showed that a delay period can also reverse the reduction of responding established by a partial reinforcement schedule. Here we describe a series of experiments that attempted to confirm Rescorla's finding and additionally assessed the impact of the delay on another well-known consequence of partial reinforcement-the partial reinforcement extinction effect (PREE). Like Rescorla, we used a Pavlovian conditioning procedure with rats, measuring magazine activity during a CS that signaled food. Unlike Rescorla, we did not find that responding acquired under partial reinforcement spontaneously increased after a delay; however, we did observe a significant reduction in the PREE after that delay. We conclude that the passage of time has a selective effect on the retrieval of memories of nonreinforcement. Therefore, time produces spontaneous recovery by impairing retrieval of extinction memories but also weakens the PREE by impairing retrieval of memories of nonreinforcement that were acquired during partial reinforcement. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Dissociating reward sensitivity and negative urgency effects on impulsivity in the five-choice serial reaction time task.

Negative urgency describes the tendency for rash and impulsive behaviour during negative emotional states and has been linked to a number of psychiatric disorders. However, there has been limited research on negative urgency as an explanatory mechanism for impulsivity in experimental animals. Such research has important implications for elucidating the neurobiology of negative urgency and thereby the development of future therapeutic interventions. In this study, we investigated the effects of negative urgency using a partial reinforcement schedule to increase the frequency of non-rewarded (i.e. frustrative) trials in the five-choice serial reaction time task, a widely used task to assess visual attention and impulsivity. Using a Markov chain model to analyse trial-by-trial outcomes we found that premature (i.e. impulsive) responses in the five-choice serial reaction time task were more likely to occur after a non-rewarded trial, and mostly after a previous premature trial. However, contrary to the frustration hypothesis of negative urgency, increasing the probability of reinforcement (p(R)) from p(R) = 0.5 to p(R) = 1 increased the number of premature responses in each session. Micro and macro levels of analyses revealed that impulsivity in the five-choice serial reaction time task is governed by at least two processes, one dependent on the overall level of reinforcement hypothesised to determine the state of behavioural activation, the second dependent on trial-by-trial outcomes consistent with negative urgency effects. These processes may depend on distinct neurobiological mechanisms and have relevance for neuropsychiatric disorders that implicate impulsive behaviours dependent on positive and negative affective states.

Boundary conditions of post-retrieval extinction: A direct comparison of low and high partial reinforcement

Research has shown that a single presentation of the conditioned stimulus prior to extinction training can diminish conditioned responses. However, replication has proven difficult and appears to be limited by boundary conditions. Here we tested the boundary condition of memory strength by comparing the effect of reinforcement rate to assess its role in post-retrieval extinction. Eighty university students had undergone a three-day fear conditioning experiment in which two partial reinforcement schedules (40%, 80%) were applied. The findings indicated that both low and high partial reinforcement groups did not demonstrate recovery of conditioned responses after post-retrieval extinction. In contrast, both groups demonstrated significant recovery to standard extinction with significantly greater recovery in the 80% group relative to the 40% group. Additionally, we found that greater physiological arousal during memory retrieval significantly predicted recovery of fear at test phase. We conclude that when compared to a lower partial reinforcement schedule, a higher partial reinforcement resulted in the formation of a stronger memory as indicated by greater physiological arousal during memory reactivation and recovery of conditioned responses after standard extinction, but that it does not function as a boundary condition of post-retrieval extinction. These data are significant because it is the first study to investigate the effect of varying partial reinforcement schedules on fear recovery and add to the body of literature that continue to identify sources of failure in the application of post-retrieval extinction.

The importance of trials.

Many theories of conditioning describe learning as a process by which stored information about the relationship between a conditioned stimulus (CS) and unconditioned stimulus (US) is progressively updated upon each occasion (trial) that the CS occurs with, or without, the US. These simple trial-based descriptions can provide a powerful and efficient means of extracting information about the correlation between 2 events, but they fail to explain how animals learn about the timing of events. This failure has motivated models of conditioning in which animals learn continuously, either by explicitly representing temporal intervals between events or by sequentially updating an array of associations between temporally distributed elements of the CS and US. Here, I review evidence that some aspects of conditioning are not the consequence of a continuous learning process but reflect a trial-based process. In particular, the way that animals learn about the absence of a predicted US during extinction suggests that they encode and remember trials as single complete episodes rather than as a continuous experience of unfulfilled expectation of the US. These memories allow the animal to recognize repeated instances of nonreinforcement and encode these as a sequence that, in the case of a partial reinforcement schedule, can become associated with the US. The animal is thus able to remember details about the pattern of a CS's reinforcement history, information that affects how long the animal continues to respond to the CS when all reinforcement ceases. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The partial reinforcement extinction effect: The proportion of trials reinforced during conditioning predicts the number of trials to extinction.

Four experiments compared the extinction of responding to a continuously reinforced (CRf) conditioned stimulus (conditional stimulus [CS]) consistently reinforced on every trial, with extinction of responding to a partially reinforced (PRf) CS that had been inconsistently reinforced. To equate the acquisition of responding between the two CSs, the average duration of the CRf CS was extended so that it scheduled the same overall rate of reinforcement per unit time as the PRf CS. Experiment 1 used a within-subjects design to compare the rates of extinction for a 10-s PRf CS reinforced on 33% of trials versus a 30-s CRf CS. Experiment 2 made the same comparison but using a between-subjects design. Experiment 3 compared extinction in a group trained with a 10-s PRf CS reinforced on 20% of trials and a group trained with a 50-s CRf CS. Experiment 4 compared the rates of extinction following two partial reinforcement schedules: a 10-s PRf CS reinforced on 33% of trial versus a 20-s CRf CS reinforced on 66% of trials. In each experiment, responding took longer to extinguish for the CS that scheduled a lower per-trial probability of reinforcement. Modeling of individual extinction curves using Weibull functions indicated that the latency to initiate extinction was directly related to the per-trial probability of reinforcement learned during acquisition. For example, compared with training with a CRf CS, rats reinforced on 33% of trials took approximately 3 times as many trials to initiate extinction, and rats reinforced on 20% of trials took 5 times as many trials to initiate extinction. These results provide support for trial-based accounts of extinction (e.g., Capaldi & Deutsch, 1967), whereby rats learn about the expected number of trials per reinforcer, and extinction depends on the number of expected reinforcers that have been omitted rather than on the number of extinction trials per se. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Saving the Perruchet effect: A role for the strength of the association in associative learning.

In a partial reinforcement schedule where a cue repeatedly predicts the occurrence of a target in consecutive trials, reaction times to the target tend to decrease in a monotonic fashion, while participants' expectancies for the target decrease at the same time. This dissociation between reaction times and expectancies-the so-called Perruchet effect-challenges the propositional view of learning, which posits that human conditioned responses result from conscious inferences about the relationships between events. However, whether the reaction time pattern reflects the strength of a putative cue-target link, or only non-associative processes, such as motor priming, remains unclear. To address this issue, we implemented the Perruchet procedure in a two-choice reaction time task and compared reaction time patterns in an Experimental condition, in which a tone systematically preceded a visual target, and in a Control condition, in which the onset of the two stimuli were uncoupled. Participants' expectancies regarding the target were recorded separately in an initial block. Reaction times decreased with the succession of identical trials in both conditions, reflecting the impact of motor priming. Importantly, reaction time slopes were steeper in the Experimental than in the Control condition, indicating an additional influence of the associative strength between the two stimuli. Interestingly, slopes were less steep for participants who showed the gambler's fallacy in the initial block. In sum, our results suggest the mutual influences of motor priming, associative strength, and expectancies on performance. They are in line with a dual-process model of learning involving both a propositional reasoning process and an automatic link-formation mechanism.

The distressed (Type D) personality factor of social inhibition, but not negative affectivity, enhances eyeblink conditioning

Recent work has focused on a learning diathesis model in which specific personality factors such as behavioral inhibition (BI) may influence associative learning and in turn increase risk for the development of anxiety disorders. We have found in a series of studies that individuals self-reporting high levels of BI exhibit enhanced acquisition of conditioned eyeblinks. In the study reported here, hypotheses were extended to include distressed (Type D) personality which has been found to be related to BI. Type D personality is measured with the DS-14 scale which includes two subscales measuring negative affectivity (NA) and social inhibition (SI). We hypothesized that SI, which is similar to BI, would result in enhanced acquisition while the effect of NA is unclear. Eighty nine participants completed personality inventories including the Adult Measure of Behavioral Inhibition (AMBI) and DS-14. All participants received 60 acquisition trials with a 500 ms, 1000 Hz, tone CS and a co-terminating 50 ms, 5 psi corneal airpuff US. Participants received either 100% CS-US paired trials or a schedule of partial reinforcement where 50% US alone trials were intermixed into CS-US training. Acquisition of CRs did not differ between the two training protocols. Whereas BI was significantly related to Type D, SI, and NA, only BI and SI individuals exhibited enhanced acquisition of conditioned eyeblinks as compared to non-inhibited individuals. Personality factors now including social inhibition can be used to identify individuals who express enhanced associative learning which lends further support to a learning diathesis model of anxiety disorders.

Turning negative memories around: Contingency versus devaluation techniques

Background and objectivesIt is assumed that fear responses can be altered by changing the contingency between a conditioned stimulus (CS) and an unconditioned stimulus (US), or by devaluing the present mental representation of the US. The aim of the present study was to compare the efficacy of contingency- and devaluation-based intervention techniques on the diminishment in – and return of fear. We hypothesized that extinction (EXT, contingency-based) would outperform devaluation-based techniques regarding contingency measures, but that devaluation-based techniques would be most effective in reducing the mental representation of the US. Additionally, we expected that incorporations of the US during devaluation would result in less reinstatement of the US averseness. MethodsHealthy participants received a fear conditioning paradigm followed by one of three interventions: extinction (EXT, contingency-based), imagery rescripting (ImRs, devaluation-based) or eye movement desensitization and reprocessing (EMDR, devaluation-based). A reinstatement procedure and test followed the next day. ResultsEXT was indeed most successful in diminishing contingency-based US expectancies and skin conductance responses (SCRs), but all interventions were equally successful in reducing the averseness of the mental US representation. After reinstatement EXT showed lowest expectancies and SCRs; no differences were observed between the conditions concerning the mental US representation. LimitationsA partial reinforcement schedule was used, resulting in a vast amount of contingency unaware participants. Additionally, a non-clinical sample was used, which may limit the generalizability to clinical populations. ConclusionEXT is most effective in reducing conditioned fear responses.

Bayesian methods for addressing long-standing problems in associative learning: The case of PREE.

Most associative models typically assume that learning can be understood as a gradual change in associative strength that captures the situation into one single parameter, or representational state. We will call this view single-state learning. However, there is ample evidence showing that under many circumstances different relationships that share features can be learned independently, and animals can quickly switch between expressing one or another. We will call this multiple-state learning. Theoretically, it is understudied because it needs a different data analysis approach from those usually employed. In this article, we present a Bayesian model of the Partial Reinforcement Extinction Effect (PREE) that can test the predictions of the multiple-state view. This implies estimating the moment of change in the responses (from the acquisition to the extinction performance), both at the individual and group levels. We used this model to analyze data from a PREE experiment with three levels of reinforcement during acquisition (100%, 75% and 50%). We found differences in the estimated moment of switch between states during extinction, so that it was delayed after leaner partial reinforcement schedules. The finding is compatible with the multiple-state view. It is the first time, to our knowledge, that the predictions from the multiple-state view are tested directly. The article also aims to show the benefits that Bayesian methods can bring to the associative learning field.

Facilitated acquisition of the classically conditioned eyeblink response in active duty military expressing posttraumatic stress disorder symptoms

ObjectiveLearning diathesis models underscore the role of hyper-conditioning in the development of PTSD following trauma exposure. Eyeblink classical conditioning is one method of examining associative learning biases independent of fear and threat produced by trauma. Facilitated learning is apparent in individuals self-expressing PTSD symptoms, as well as behaviorally inhibited (BI) temperament, a vulnerability factor for PTSD. Here, we examine eyeblink conditioning in active duty military personnel and relate learning with PTSD symptomology. MethodVolunteers were 83 active duty United States Coast Guard personnel (18 females) recruited from small boat stations. Personnel were administered the PTSD Checklist (PCL) to assess current PTSD symptoms using DSM-IV criteria. BI temperament was assessed with the Adult Measure of Behavioural Inhibition (AMBI). Eyeblink conditioning was conducted using a partial reinforcement schedule, whereby paired trials (500-ms pure tone conditioned stimulus co-terminating with a 50-ms air-puff unconditional stimulus) were interpolated with 50% CS-alone trials. ResultsConsistent with previous work, there was a high degree of concordance between BI and incidence of PTSD. Further, PTSD was associated with faster learning during the acquisition period, with conditioned responding sustained through the extinction period. ConclusionsThese results reinforce the relationship between BI and PTSD in an active duty military sample, supporting previous observations in veteran and civilian samples. The conditioning data are consistent with predictions derived from a learning diathesis model of stress and anxiety, suggesting facilitated associative learning may represent an additional vulnerability for the development and maintenance of stress-related pathology.

Hippocampal Processing of Ambiguity Enhances Fear Memory

Despite the ubiquitous use of Pavlovian fear conditioning as a model for fear learning, the highly predictable conditions used in the laboratory do not resemble real-world conditions, in which dangerous situations can lead to unpleasant outcomes in unpredictable ways. In the current experiments, we varied the timing of aversive events after predictive cues in rodents and discovered that temporal ambiguity of aversive events greatly enhances fear. During fear conditioning with unpredictably timed aversive events, pharmacological inactivation of the dorsal hippocampus or optogenetic silencing of cornu ammonis 1 cells during aversive negative prediction errors prevented this enhancement of fear without affecting fear learning for predictable events. Dorsal hippocampal inactivation also prevented ambiguity-related enhancement of fear during auditory fear conditioning under a partial-reinforcement schedule. These results reveal that information about the timing and occurrence of aversive events is rapidly acquired and that unexpectedly timed or omitted aversive events generate hippocampal signals to enhance fear learning.

Uncertainty of trial timing enhances acquisition of conditioned eyeblinks in anxiety vulnerable individuals

Recent work has found that behaviorally inhibited (BI) individuals exhibit enhanced eyeblink conditioning in omission and yoked training as well as with schedules of partial reinforcement. We hypothesized that spacing CS-US paired trials over a longer period of time by extending and varying the inter-trial interval (ITI) would facilitate learning. All participants completed the Adult Measure of Behavioural Inhibition (AMBI) and were grouped as behaviorally inhibited (BI) and non-behaviorally inhibited (NI) based on a median split score of 15.5. All participants received 3 US alone trials and 30CS-US paired trials for acquisition training and 20CS alone trials for extinction training in one session. Conditioning stimuli were a 500ms tone conditioned stimulus (CS) and a 50-ms air puff unconditional stimulus (US). Participants were randomly assigned to receive a short ITI (mean=30+/− 5s), a long ITI (mean=57+/− 5s) or a variable long ITI (mean=57s, range 25–123s). No significant ITI effects were observed for acquisition or extinction. Overall, anxiety vulnerable individuals exhibited enhanced conditioned eyeblink responses as compared to non-vulnerable individuals. This enhanced acquisition of CRs was significant in spaced training with a variable long ITI, but not the short or long ITI. There were no significant effects of ITI or BI on extinction. These findings are interpreted based on the idea that uncertainty plays a role in anxiety and can enhance associative learning in anxiety vulnerable individuals.

Classroom Reinforcement Schedules and Their Effectiveness in Selected Kenyan Primary Schools

The purpose of the study was to determine Classroom Reinforcement Schedules and Their Effectiveness in Selected Kenyan Primary Schools. The study employed a Mixed Methods design in which both quantitative and qualitative data were collected. The target population teachers and pupils from public primary schools. Data was collected by using questionnaires and interview schedules. Quantitative data was analyzed using inferential statistics while Qualitative data was analyzed by using the thematic and content analysis. The study reported on the use of praise, tangible items such as games and money were also moderately often used by the teachers. The participants also used both Continuous reinforcement and partial reinforcement schedules. The study recommends that, schools should enhance token economy programs which have long term effect. Moreover, teachers should deepen their knowledge on token economy programs for academic success. DOI: 10.5901/jesr.2015.v5n3p41

Dissociating conscious expectancies from automatic-link formation in an electrodermal conditioning paradigm.

The key point of a paradigm initially proposed by Perruchet (Pavlov J Biol Sci 20:163-170, 1985) to dissociate conscious expectancies from automatic-link formation in classical conditioning settings is the use of a partial reinforcement schedule, in which the unconditioned stimulus (US) follows the conditioned stimulus (CS) only half of the time on average. Given (pseudo) randomization, the whole sequence comprises runs of CS alone and runs of CS-US pairs of various lengths. When the preceding run goes from a long sequence of CS alone to a long sequence of CS-US pairs (via shorter sequences), associative strength should grow up, whereas conscious expectancy should decrease. Earlier studies have shown that, in most cases, conditioned performance parallels associative strength. As an exception, however, a few reports suggest that conditioned electrodermal responses (EDRs) would follow predicted changes in US expectancies. This paper presents an experiment that replicates this outcome. However, when the performances from a control group were taken as a baseline to control for response habituation, corrected conditioned EDRs were shown to follow associative strength. This suggests that the atypical pattern of conditioned EDRs in the Perruchet paradigm would be due to the fact that EDRs are more sensitive to habituation than responses involved in other associative learning settings. These results further challenge the recent "propositional" view of conditioning, which stipulates that conditioned responses in humans are the consequence of participants' conscious inferences about the relationships between the CS and the US, which would lead the CS to generate conscious expectancy for the US.

Avoidance prone individuals self reporting behavioral inhibition exhibit facilitated acquisition and altered extinction of conditioned eyeblinks with partial reinforcement schedules.

Avoidance in the face of novel situations or uncertainty is a prime feature of behavioral inhibition which has been put forth as a risk factor for the development of anxiety disorders. Recent work has found that behaviorally inhibited (BI) individuals acquire conditioned eyeblinks faster than non-inhibited (NI) individuals in omission and yoked paradigms in which the predictive relationship between the conditioned stimulus (CS) and unconditional stimulus (US) is less than optimal as compared to standard training with CS-US paired trials (Holloway et al., 2014). In the current study, we tested explicitly partial schedules in which half the trials were CS alone or US alone trials in addition to the standard CS-US paired trials. One hundred and forty nine college-aged undergraduates participated in the study. All participants completed the Adult Measure of Behavioral Inhibition (i.e., AMBI) which was used to group participants as BI and NI. Eyeblink conditioning consisted of three US alone trials, 60 acquisition trials, and 20 CS-alone extinction trials presented in one session. Conditioning stimuli were a 500 ms tone CS and a 50-ms air puff US. Behaviorally inhibited individuals receiving 50% partial reinforcement with CS alone or US alone trials produced facilitated acquisition as compared to NI individuals. A partial reinforcement extinction effect (PREE) was evident with CS alone trials in BI but not NI individuals. These current findings indicate that avoidance prone individuals self-reporting behavioral inhibition over-learn an association and are slow to extinguish conditioned responses (CRs) when there is some level of uncertainty between paired trials and CS or US alone presentations.

How partial reinforcement of food cues affects the extinction and reacquisition of appetitive responses. A new model for dieting success?

Animals and humans can easily learn to associate an initially neutral cue with food intake through classical conditioning, but extinction of learned appetitive responses can be more difficult. Intermittent or partial reinforcement of food cues causes especially persistent behaviour in animals: after exposure to such learning schedules, the decline in responding that occurs during extinction is slow. After extinction, increases in responding with renewed reinforcement of food cues (reacquisition) might be less rapid after acquisition with partial reinforcement. In humans, it may be that the eating behaviour of some individuals resembles partial reinforcement schedules to a greater extent, possibly affecting dieting success by interacting with extinction and reacquisition. Furthermore, impulsivity has been associated with less successful dieting, and this association might be explained by impulsivity affecting the learning and extinction of appetitive responses. In the present two studies, the effects of different reinforcement schedules and impulsivity on the acquisition, extinction, and reacquisition of appetitive responses were investigated in a conditioning paradigm involving food rewards in healthy humans. Overall, the results indicate both partial reinforcement schedules and, possibly, impulsivity to be associated with worse extinction performance. A new model of dieting success is proposed: learning histories and, perhaps, certain personality traits (impulsivity) can interfere with the extinction and reacquisition of appetitive responses to food cues and they may be causally related to unsuccessful dieting.

The effect of early‐life stress on memory systems supporting instrumental behavior

People experiencing early-life stress (ELS) exhibit increased incidence of behaviors that lead to addiction and obesity as adults. Many of these behaviors may be viewed as resulting from an overreliance on habits as opposed to goal-directed instrumental behavior. This increased habitization may result from alterations in the interactions between dorsolateral striatum-dependent and hippocampus-dependent learning systems. As an initial examination of this idea, we investigated the effect of ELS on instrumental learning and extinction. In Experiment 1, we examined the effect of ELS in two groups of people, one trained on a continuous reinforcement schedule and one trained on a partial reinforcement schedule. We found that people who experienced ELS had a diminished effect of the partial reinforcement schedule on extinction. In Experiment 2, we again manipulated reinforcement schedule and also challenged declarative memory by requiring subjects to perform a concurrent task. We found that the declarative challenge did not affect extinction responding in the non-ELS group. In a moderate-ELS group, we observed a diminished sensitivity to the reinforcement schedule during extinction only under divided attention. In the high-ELS group, we observed a reduced sensitivity to reinforcement schedule even in the absence of the declarative memory challenge, consistent with Experiment 1. Our results suggest that ELS reduces the tendency to use declarative, hippocampus-dependent memory in instrumental tasks in favor of habits. ELS may affect hippocampal development, thus altering the interaction between memory systems and potentially contributing to poor health outcomes.

Influence of the reinforcement magnitude on omission effects

Reinforcement Omission Effects (ROEs), indicated by higher rate of responses after nonreinforced trials in a partial reinforcement schedule, have been interpreted as behavioral transient facilitation after nonreinforcement induced by primary frustration, and/or behavioral transient inhibition after reinforcement induced by demotivation or temporal control. The size of the ROEs should depend directly on the reinforcement magnitude. The present experiment aimed to clarify the relationship between reinforcement magnitude and the omission effects manipulating the magnitude linked to discriminative stimuli in a partial reinforcement FI schedule. The results showed that response rates were higher after omission than after reinforcement delivery. Besides, response rates were highest immediately after the reinforcement omission of a larger magnitude than of a smaller magnitude. These data are interpreted in terms of ROEs multiple process behavioral facilitation after nonreinforcement, and behavioral transient inhibition after reinforcement.

Classical and instrumental conditioning of eyeblink responses in Wistar–Kyoto and Sprague–Dawley rats

Wistar–Kyoto (WKY) rats, an animal model of anxiety vulnerability, acquire lever-press avoidance faster than outbred Sprague–Dawley (SD) rats. Faster avoidance acquisition may reflect an inherent ability to acquire cue–outcome associations, response–outcome associations or both. To evaluate cue–outcome learning, acquisition of classically conditioned eyeblink response was compared in SD and WKY rats using a delay-type paradigm (500-ms conditioned stimulus (CS) coterminating with a 10-ms unconditional stimulus (US)). WKY rats demonstrated enhanced classical conditioning, with both faster acquisition and greater asymptotic performance in delay-type training than SD rats. To evaluate response–outcome learning, separate SD and WKY rats were given control over US delivery through imposition of an omission contingency into delay-type training (emitting a conditioned response (CR) prevented delivery of the US). The schedule of US delivery derived by these rats became the training regimen for a separate group of SD and WKY rats, yoked within strain. In SD rats, no differences in acquisition were detected between those given control over US delivery and those trained with the same partial reinforcement schedule. Acquisition rates of those WKY rats with control exceeded those trained with a yoked-schedule of US presentation. Collectively, WKY rats exhibit enhanced classical conditioning and sensitivity to schedules of reinforcement compared to outbred SD rats. Anxiety vulnerability, in particular inhibited temperament, may be traced to active processes in the prediction and control of aversive events.

Do reaction times in the perruchet effect reflect variations in the strength of an associative link?

In 3 experiments, we examined Perruchet, Cleeremans, and Destrebecqz's (2006) double dissociation of cued reaction time (RT) and target expectancy. In this design, participants receive a tone on every trial and are required to respond as quickly as possible to a square presented on 50% of those trials (a partial reinforcement schedule). Participants are faster to respond to the square following many recent tone-square pairings and slower to respond following many tone-alone presentations. Of importance, expectancy of the square is highest when performance on the RT task is poorest-following many tone-alone trials. This finding suggests that RT performance is determined by the strength of a tone-square link and that this link is the product of a non-expectancy-based learning mechanism. The present experiments, however, provide evidence that the speeded RTs are not the consequence of the strengthening and weakening of a tone-square link. Thus, the RT Perruchet effect does not provide evidence for a non-expectancy-based link-formation mechanism.