Interresponse Times Research Articles

Extinction-Induced Variability in Human Behavior

Participants earned points by pressing a computer space bar (Experiment 1) or forming rectangles on the screen with the mouse (Experiment 2) under differential-reinforcement-of-low-rate schedules, followed by extinction. Variability in interresponse time (the contingent dimension) increased during extinction, as for Morgan and Lee (1996); variability in diagonal length (the noncontingent dimension, Experiment 2) did not. In Experiment 3, points were contingent on rectangle size. Rectangle size and interresponse-time (the noncontingent dimension) variability increased in extinction. There was greater variability in the contingent dimension during extinction for participants with the more varied history of reinforcement in Experiment 2 but not in Experiment 3. Overall, variability in the contingent dimension increased in extinction, but the degree of increase was affected by reinforcement history.

Effects of Unequal Inter and Intra-Toroid Response Times on the Quench Performance of the System of Three ATLAS Toroids

The ATLAS Experiment at the LHC (CERN) has a toroidal magnet system composed of one barrel toroid and two end cap toroids powered in series at 20.5 kA with a total stored energy of 1.6 GJ. So far the three magnets have been tested independently. In preparation of the overall magnet system test, here we review the quench behavior under normal and faulty conditions including the information gained from the test of the three single magnets. In particular the consequences of variations in effective quench detection and quench heater activation times are studied. The effects on energy re-distribution, peak temperatures and internal voltage in the three toroids and between the 8 coils within a single toroid are investigated. Based on simulation studies partly verified by experiments, conclusions regarding the quench performance of the entire system are drawn.

Detecting changes in simulated events II: Using variations of momentary time‐sampling to measure changes in duration events

AbstractThe extent to which a greater proportion of small behavior changes could be detected with momentary time‐sampling (MTS) was evaluated by (a) combining various interval sizes of partial‐interval recording (PIR) with 20 s, 30 s, 1 min MTS and (b) using variable interval sizes of MTS that were based on means of 20 s and 1 min. For each targeted percentage, low, moderate, and high inter‐response times (IRTs) to event‐run ratios were compared with reversal designs to determine whether sensitivity increased with either variation of MTS. The results showed that (a) combinations of 30 s and 1 min MTS/PIR yielded increased sensitivity over MTS alone; however, the increased sensitivity was offset by an increased probability of generating false positives and (b) variable‐interval MTS produced comparable sensitivity to fixed‐interval MTS. Thus, none of the methods increased detection of small behavior changes (decreased false negatives) without also increasing false positives. Copyright © 2009 John Wiley & Sons, Ltd.

High-rate operant behavior in two mouse strains: A response-bout analysis

Operant behavior sometimes occurs in bouts characterized by an initiation rate, within-bout response rate, and bout length. The generality of this structure was tested using high-rate nose-poking in mice. Reinforcement of short interresponse times produced high response rates while a random-interval schedule held reinforcement rates constant. BALB/c mice produced bouts that were more frequent, longer, and contained a higher within-bout rate of responding (nine nose-pokes/s) than did the C57BL/6 mice (five nose-pokes/s). Adding a running wheel decreased total nose-pokes and bout length, and increased bout-initiation rate. Free-feeding reduced nose-poking by decreasing bout-initiation rate. Photoperiod reversal decreased bout-initiation rate but not total nose-poke rate. Despite strain differences in bout structure, both strains responded similarly to the interventions. The three bout measures were correlated with overall rate but not with each other. Log-survival analyses provided independent descriptors of the structure of high-rate responding in these two strains.

SINGLE‐SAMPLE DISCRIMINATION OF DIFFERENT SCHEDULES' REINFORCED INTERRESPONSE TIMES

Food-deprived rats in Experiment 1 responded to one of two tandem schedules that were, with equal probability, associated with a sample lever. The tandem schedules' initial links were different random-interval schedules. Their values were adjusted to approximate equality in time to completing each tandem schedule's response requirements. The tandem schedules differed in their terminal links: One reinforced short interresponse times; the other reinforced long ones. Tandem-schedule completion presented two comparison levers, one of which was associated with each tandem schedule. Pressing the lever associated with the sample-lever tandem schedule produced a food pellet. Pressing the other produced a blackout. The difference between terminal-link reinforced interresponse times varied across 10-trial blocks within a session. Conditional-discrimination accuracy increased with the size of the temporal difference between terminal-link reinforced interresponse times. In Experiment 2, one tandem schedule was replaced by a random ratio, while the comparison schedule was either a tandem schedule that only reinforced long interresponse times or a random-interval schedule. Again, conditional-discrimination accuracy increased with the temporal difference between the two schedules' reinforced interresponse times. Most rats mastered the discrimination between random ratio and random interval, showing that the interresponse times reinforced by these schedules can serve to discriminate between these schedules.

AGGRESSION AS POSITIVE REINFORCEMENT IN MICE UNDER VARIOUS RATIO‐ AND TIME‐BASED REINFORCEMENT SCHEDULES

There is evidence suggesting aggression may be a positive reinforcer in many species. However, only a few studies have examined the characteristics of aggression as a positive reinforcer in mice. Four types of reinforcement schedules were examined in the current experiment using male Swiss CFW albino mice in a resident-intruder model of aggression as a positive reinforcer. A nose poke response on an operant conditioning panel was reinforced under fixed-ratio (FR 8), fixed-interval (FI 5-min), progressive ratio (PR 2), or differential reinforcement of low rate behavior reinforcement schedules (DRL 40-s and DRL 80-s). In the FR conditions, nose pokes were maintained by aggression and extinguished when the aggression contingency was removed. There were long postreinforcement pauses followed by bursts of responses with short interresponse times (IRTs). In the FI conditions, nose pokes were maintained by aggression, occurred more frequently as the interval elapsed, and extinguished when the contingency was removed. In the PR conditions, nose pokes were maintained by aggression, postreinforcement pauses increased as the ratio requirement increased, and responding was extinguished when the aggression contingency was removed. In the DRL conditions, the nose poke rate decreased, while the proportional distributions of IRTs and postreinforcement pauses shifted toward longer durations as the DRL interval increased. However, most responses occurred before the minimum IRT interval elapsed, suggesting weak temporal control of behavior. Overall, the findings suggest aggression can be a positive reinforcer for nose poke responses in mice on ratio- and time-based reinforcement schedules.

Beyond continuous mathematics and traditional scientific analysis: Understanding and mining Wolfram's A New Kind of Science

In A New Kind of Science, Stephen Wolfram recommends abandoning traditional scientific analysis and the continuous mathematical description that it affords in favor of the study of simple rules. He focuses on a machine known as a cellular automaton as the prototype generator of complex phenomena such as those we see in nature. The simplest cellular automaton consists of a row of cells, each existing in one of two states. The states of the cells are updated from moment to moment by simple rules. Wolfram shows that these machines and their many variations can generate a host of outcomes ranging from very simple to extremely complex. He argues that among these outcomes representations of all the phenomena in the universe will be found, including presumably the behavior of organisms. The output of cellular automata can be mapped to behavior by considering, for example, one of the states of a cell to represent the emission of a behavior. For some cellular automaton rules, these mappings generate cumulative records and inter-response time distributions that are similar to those produced by live organisms. In addition, at least one cellular automaton generates the Herrnstein hyperbola as an emergent outcome. These results suggest that Wolfram's program and its mainstream version, which is known as complexity theory, is worth pursuing as a possible means of understanding and accounting for the behavior of organisms.

Timing and space usage are disrupted by amphetamine in rats maintained on DRL 24-s and DRL 72-s schedules of reinforcement

A differential-reinforcement-of-low-rate schedule (DRL) delivers reinforcement only when the interresponse time (IRT) exceeds a fixed time interval, thereby shaping rats to discriminate the timing of their responses. However, little is known about the motor behavior and location of the rats in the chamber during the IRTs that lead to reinforcement. Although amphetamine is known to disrupt DRL timing behavior, the effects of this drug on non-operant motor behavior during DRL performance has not yet been quantified. The purpose of this research was to measure the motor behavior (movement trajectories in the horizontal plane and spatial location in the plane) during longer IRTs after either vehicle or amphetamine treatment. Experimental chambers were constructed with a force-plate actometer as the floor, and while performing the operant task, the rats' motor behaviors were measured continuously with high temporal and spatial resolution. Separate groups of eight male Sprague-Dawley rats were maintained on either DRL 24-s or DRL 72-s schedules of water reinforcement in 4-h recording sessions. Analyses of IRT distributions showed that the rats' timing behavior conformed to their respective DRL requirements. In the absence of drug, analysis of motor behavior in pre-reinforcement intervals showed that rats located themselves away from the operandum and exhibited very low levels of movement. Rats exhibited a significant temporal diminution of horizontal movement that reached a minimum 4-8 s before the rats moved to the operandum to execute operant responses. Amphetamine treatment increased locomotion, abolished the temporal movement gradient, and brought the rats closer to the operandum compared to vehicle treatment. Movement changes induced by amphetamine were accompanied by degraded timing behavior. Taken together, the data show that DRL training induced rats to locate themselves away from the operandum and to remain nearly motionless during longer IRTs and that amphetamine treatment interfered with this complex of behavioral features.

Effects of adjusting DRO schedules on the reduction of stereotypic vocalizations in children with autism

AbstractThe reduction of stereotypic behavior is important for individuals with developmental disabilities because it may interfere with learning new skills. A common procedure used to reduce stereotypic behavior is differential reinforcement of other behavior (DRO). A DRO schedule is a procedure in which reinforcement is delivered given the absence of a target response for a period of time. Although DRO schedules have been shown to be effective in reducing a variety of stereotypic behavior, empirical studies have not yet determined the most effective way to thin the reinforcement schedule. The current study examined the extent to which the relationship between the inter‐response time (IRT) and the DRO requirement affects the reduction of stereotypic behavior. Results of the current study showed the DRO requirement that was set to the 25th percentile of the IRT distribution was more effective in reducing stereotypic behavior when compared with a DRO requirement set to the 95th percentile of the IRT distribution. Copyright © 2009 John Wiley & Sons, Ltd.

An application of the active time model to multiple concurrent variable-interval schedules

The current experiment investigates whether an active time model can account for anomalous results that have emerged from multiple schedule, concurrent variable-interval (VI) VI experiments. The model assumes that (1) during concurrent VI VI training pigeons learn a function that relates time since the most immediate response, i.e., active time, to changeover probabilities and (2) that molar preference is the result of an interaction between inter-response time frequencies and the learned active time changeover functions. Pigeons were trained under a concurrent VI 30-s VI 30-s schedule and a concurrent VI 60-s VI 60-s schedule. Probes were conducted in which VI 30-s and VI 60-s stimuli were paired. During these probes, birds allocated choices equally to the stimuli. The active time model accurately fit individual subject data. In contrast data were not fit by a variant of scalar expectancy theory proposed by Gibbon [Gibbon, J., 1995. Dynamics of time matching: arousal makes better seem worse. Psychon. Bull. Rev. 2, 208-215].

INTERRESPONSE TIME STRUCTURES IN VARIABLE‐RATIO AND VARIABLE‐INTERVAL SCHEDULES

The interresponse-time structures of pigeon key pecking were examined under variable-ratio, variable-interval, and variable-interval plus linear feedback schedules. Whereas the variable-ratio and variable-interval plus linear feedback schedules generally resulted in a distinct group of short interresponse times and a broad distribution of longer interresponse times, the variable-interval schedules generally showed a much more continuous distribution of interresponse times. The results were taken to indicate that a log survivor analysis or double exponential fit of interresponse times may not be universally applicable to the task of demonstrating that operant behavior can be dichotomized into bouts of engagement and periods of disengagement.

AN ANALYTIC FORM FOR THE INTERRESPONSE TIME ANALYSIS OF SHULL, GAYNOR, AND GRIMES WITH APPLICATIONS AND EXTENSIONS

Shull, Gaynor and Grimes advanced a model for interresponse time distribution using probabilistic cycling between a higher-rate and a lower-rate response process. Both response processes are assumed to be random in time with a constant rate. The cycling between the two processes is assumed to have a constant transition probability that is independent of bout length. This report develops an analytic form of the model which has a natural parametrization for a higher-rate within-bout responding and a lower-rate visit-initiation responding. The analytic form provides a convenient basis for both a nonlinear least-squares data reduction technique to estimate the model's parameters and Monte Carlo simulations of the model. In addition, the analytic formulation is extended to both a refractory period for the rats' behavior and, separately, the strongly-banded behavior seen with pigeons.

The 5-Hydroxytryptamine2A Receptor Antagonist R-(+)-α-(2,3-Dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl-4-piperidinemethanol (M100907) Attenuates Impulsivity after Both Drug-Induced Disruption (Dizocilpine) and Enhancement (Antidepressant Drugs) of Differential-Reinforcement-of-Low-Rate 72-s Behavior in the Rat

Previous work has suggested that N-methyl-d-aspartate (NMDA) receptor antagonism and 5-hydroxytryptamine (5-HT)(2A) receptor blockade may enhance and attenuate, respectively, certain types of impulsivity mediated by corticothalamostriatal circuits. More specifically, past demonstrations of synergistic "antidepressant-like" effects of a 5-HT(2A) receptor antagonist and fluoxetine on differential-reinforcement-of-low-rate (DRL) 72-s schedule of operant reinforcement may speak to the role of 5-HT(2A) receptor blockade with respect to response inhibition as an important prefrontal cortical executive function relating to motor impulsivity. To examine the dynamic range over which 5-HT(2A) receptor blockade may exert effects on impulsivity, [R-(+)-alpha-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl-4-piperidinemethanol] (M100907) was examined both alone and in combination with the psychotomimetic NMDA receptor antagonist dizocilpine [e.g., (-)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate; MK-801] and two different antidepressants, the tricyclic antidepressant desmethylimipramine (DMI) and the monoamine oxidase inhibitor tranylcypromine in rats performing under a DRL 72-s schedule. MK-801 increased the response rate, decreased the number of reinforcers obtained, and exerted a leftward shift in the inter-response time (IRT) distribution as expected. A dose of M100907 that exerted minimal effect on DRL behavior by itself attenuated the psychotomimetic effects of MK-801. Extending previous M100907-fluoxetine observations, addition of a minimally active dose of M100907 to low doses of DMI and tranylcypromine enhanced the antidepressant-like effect of the antidepressants. Therefore, it may be that a tonic excitation of 5-HT(2A) receptors modulates impulsivity and function of corticothalamostriatal circuits over an extensive dynamic range.

A two-stage model for concurrent sequences

Schneider and Davison [Schneider, S.M., Davison, M., 2005. Demarcated response sequences and the generalised matching law. Behav. Proc. 70, 51-61] showed that the generalised matching law applied to concurrent free-operant two-response sequences. When sufficient temporal spacing is required between the responses, however, neither the response-level nor the sequence-level forms of the generalised matching law provide good fits. An alternative "two-stage sensitivity" model with fewer free parameters features two types of sensitivity to the reinforcement contingencies on sequences. When temporal spacing between the responses is long, the "response distribution sensitivity" parameter describes sensitivity only of the individual responses to the sequence-level contingencies. At a threshold level, this sensitivity reaches a maximum. When spacing is shorter than threshold, the "response order sensitivity" parameter reflects a new sensitivity to the order of the responses within sequences. As this sensitivity approaches its maximum, sequence matching is achieved. For both stages, a changeover parameter describes bias against sequences that require changeovers between the two responses. The model fit data ranging from near-response matching with long minimum inter-response times (IRTs) to sequence matching with no minimum IRTs, using two species and a variety of sequence reinforcer distributions. Rats differed from pigeons in achieving sequence matching only at a nonzero minimum IRT. In a comparison based on pigeon data with no minimum IRT, the two-stage sensitivity model was more efficient than the generalised matching law according to the Akaike criterion. The logic of the model suggests a new way of understanding the mechanisms underlying behavioural units.

Response grouping in the psychological refractory period (PRP) paradigm: Models and contamination effects

Response grouping is a ubiquitous phenomenon in psychological refractory period (PRP) tasks, yet it hampers the analysis of dual-task performance. To account for response grouping, we developed several extended versions of the standard bottleneck model, each of which incorporates a possible grouping mechanism into this model. Computer simulations were used to assess how the predictions of the standard model would change with each grouping mechanism. One set of simulations investigated the basic effects of grouping on the means and intercorrelation of the reaction times in the two tasks, as well as the percentage of trials with short interresponse times ( IRTs). A second set of simulations examined whether response grouping would invalidate the use of PRP paradigms for localizing experimental effects. Finally, we investigated whether the post-hoc elimination of trials with short IRTs removes the contaminating effects of response grouping.

Central vs. peripheral administration of ethanol, acetaldehyde and acetate in rats: Effects on lever pressing and response initiation

The metabolites of ethanol, acetaldehyde and acetate, are biologically active, and different effects may be produced depending upon the particular metabolite and the route of administration. These studies characterized the effects of intraperitoneal (IP) vs. intraventricular (ICV) administration of ethanol, acetaldehyde, and acetate administered to male Sprague-Dawley rats. Operant behavior was assessed by conducting a detailed temporal analysis of lever pressing with rats responding on a fixed ratio 5 schedule of food reinforcement. IP administration of all three drugs produced a rate-decreasing effect on the total number of responses. Acetaldehyde and acetate were much more potent than ethanol at reducing lever pressing. The interresponse time (IRT) distribution also was more potently altered by IP administration of ethanol metabolites than by ethanol itself. The total lever pressing and IRT distributions of ethanol- and acetaldehyde- treated rats were not significantly affected when these drugs were administered ICV, while acetate produced a marked suppression of fast responses and an increase in pausing. The metabolites of ethanol are more potent than ethanol itself in terms of altering patterns of lever pressing. Thus, the effects of ethanol administration could in part be due to the actions of its biologically active metabolites.

Issues with the SIMPLE model: Comment on Brown, Neath, and Chater (2007).

SIMPLE (G. D. A. Brown, I. Neath, & N. Chater, 2007) attempts to explain data from serial recall and free recall in the same theoretical framework. While it can fit the free-recall serial-position curves that are the cornerstone of the 2-store buffer model, it does not address 2 classic issues in short-term memory research: similarity effects and presentation-rate effects. Similarity effects in free recall led to important work on organization in free recall, whereas similarity effects in serial recall led to the phonological basis of short-term memory. Presentation-rate effects operate quite differently in free and serial recall. The model also does not consider recall order effects or interresponse times in free recall, which may be problematic.

ON THE PRIMACY OF MOLECULAR PROCESSES IN DETERMINING RESPONSE RATES UNDER VARIABLE‐RATIO AND VARIABLE‐INTERVAL SCHEDULES

This study focused on variables that may account for response-rate differences under variable-ratio (VR) and variable-interval (VI) schedules of reinforcement. Four rats were exposed to VR, VI, tandem VI differential-reinforcement-of-high-rate, regulated-probability-interval, and negative-feedback schedules of reinforcement that provided the same rate of reinforcement. Response rates were higher under the VR schedule than the VI schedule, and the rates on all other schedules approximated those under the VR schedule. The median reinforced interresponse time (IRT) under the VI schedule was longer than for the other schedules. Thus, differences in reinforced IRTs correlated with differences in response rate, an outcome suggestive of the molecular control of response rate. This conclusion was complemented by the additional finding that the differences in molar reinforcement-feedback functions had little discernible impact on responding.

Schedule discrimination in a mixed schedule: Implications for models of the variable-ratio, variable-interval rate difference

In Experiment 1, each of three humans knowledgeable about operant schedules used mouse clicks to respond to a "work key" presented on a monitor. On a random half of the presentations, work-key responses that completed a variable ratio (VR) 12 produced a tone. After five tones, the work key was replaced by two report keys. Pressing the right or left report key, respectively, added or subtracted yen50 from a counter and produced the work key. On the other half of the presentations, a variable interval (VI) associated with the work key was defined so its interreinforcer intervals approximated the time it took to complete the variable ratio. After five tone-producing completions of this schedule, the report keys were presented. Left or right report-key presses, respectively, added or subtracted yen50 from the counter. Subjects achieved high yen totals. In Experiment 2, the procedure was changed by requiring an interresponse time after completion of the variable interval that approximated the duration of the reinforced interresponse time on the variable ratio. Prior to beginning, subjects were shown how a sequence of response bouts and pauses could be used to predict schedule type. Subjects again achieved high levels of accuracy. These results show humans can discriminate ratio from interval schedules even when those schedules provide the same rate of reinforcement and reinforced interresponse times.

Additional evidence for anxiolytic- and antidepressant-like activities of saredutant (SR48968), an antagonist at the neurokinin-2 receptor in various rodent-models

Central tachykinins have been shown to play a role in the modulation of stress-related behaviours. Saredutant, a tachykinin NK2 receptor antagonist, displayed mixed anxiolytic- and antidepressant-like activities in rodents. The present study aimed at further characterizing its psychotropic properties. Saredutant was tested in the rat social interaction test to further confirm its anxiolytic-like activity, and in a variety of behavioural models sensitive to antidepressant drugs. In the rat social interaction test, saredutant (20 mg/kg, i.p.) significantly increased the time spent in interaction, as did the prototypical anxiolytic agents, diazepam (1 mg/kg, i.p.) and buspirone (1 mg/kg, s.c.), but not the antidepressant, fluoxetine. In a differential reinforcement of low rate-72s task, saredutant (3 mg/kg, i.p.) displayed an antidepressant-like activity by increasing reinforced response rate and percentage of responses emitted in the inter-response time bin [49–96 s]. In bulbectomized rats, saredutant (20 mg/kg, i.p.) restored the deficit of acquisition of passive avoidance. In rat pups separated from their mother, saredutant (3–10 mg/kg, s.c.) reduced ultrasonic distress calls. Finally, in the chronic mild stress paradigm in mice, a 29-day treatment regimen with saredutant (10 mg/kg, i.p.) attenuated stress-induced physical degradation. Importantly, in the depression models, the effects of saredutant were comparable to those obtained under similar experimental conditions by reference antidepressants such as fluoxetine or imipramine. Together, these results suggest further that the NK2 receptor may represent an attractive target for the treatment of both depressive and anxiety disorders.