Search

Previous research has shown that extended exposure to delayed reinforcement results in less impulsive choice in a subsequent delay-discounting task. Some work also suggests the opposite effect: extended exposure to immediate reinforcement may result in more impulsive choice behavior in a subsequent delay-discounting task. Understanding the impact that learning histories have on impulsive choice is important and clinically relevant because of the relationship between a strong preference for smaller-sooner over larger-later reinforcement (i.e., impulsive choice) and a myriad of other problematic health behaviors, such as substance misuse. In the present experiment, we exposed 24 rats to an immediate reinforcement intervention and 24 rats to a maturation/handle control group, followed immediately by a delay-discounting task. The procedure was designed as a systematic replication that accounted for several limitations from recent similar work. Results indicated that exposure to immediate reinforcement modestly increased impulsive choice in the delay-discounting task, but the effect was not overwhelming. These findings are consistent with previous work and have implications for understanding how experience-based interventions may affect clinically relevant impulsive choice. [ABSTRACT FROM AUTHOR]

Recently it has been proposed that impairments related to autism spectrum disorder (ASD) may reflect a more fundamental disruption in time perception. Here, we examined whether in utero exposure to valproic acid (VPA) can generate specific behavioral deficits related to ASD and time perception. Pups from control and VPA groups were tested using fixed-interval (FI) temporal bisection, peak interval, and intertemporal choice tasks. In addition, the rats were assessed on motor function, perseverative and exploratory behavior, anxiety, and memory. The VPA group displayed a leftward shift in timing functions. VPA rats displayed no deficits on the motor and memory tasks, but were significantly different from controls on measures of perseveration and anxiety. [ABSTRACT FROM AUTHOR]

Rodent models are commonly used in behavioral research because they offer increased experimental control and findings often generalizable to humans. However, one possible dilemma is that rodents are primarily nocturnal and research tasks often disrupt their light, rest phase. The present study used a within-subjects design to investigate possible effects of light-dark phase on delay discounting, motor coordination, open field, and elevated-plus maze behavior in Wistar rats. Rats spent significantly more time in the closed arms of the elevated plus maze when tested during the light, rest phase compared to the dark, active phase. There were no differences in motor coordination or delay discounting during the two phases. These results suggest possible important differences in certain behavioral tasks when testing in the light, rest versus dark, active phase for rats—researchers should be aware of these possible differences when planning and conducting experiments and when comparing research findings across laboratories. [ABSTRACT FROM AUTHOR]

Recent research has indicated high economic and environmental costs of human paper usage. Technologies have been developed to reduce consumers' paper use behavior, including mechanical dispensers that institute a delay between opportunities to obtain each consecutive unit. However, there is no empirical evidence that these dispensers or delays reduce paper use. In Experiment 1, implementing a delay between paper-unit deliveries using mechanical dispensers in a university café resulted in a significant decrease in units per person, material per person, and cost per person, compared to free-access dispensers. In Experiment 2, a relatively long delay was more effective than a short delay in reducing paper consumption in a laboratory experiment using mechanical dispensers. These results indicate that delays could be used to decrease paper use in many contexts on a larger scale. More research is necessary to determine the underlying behavioral mechanisms responsible for the observed reduction and the cost–benefit relationship under different circumstances. [ABSTRACT FROM AUTHOR]

Highlights • Exposure to delayed rewards increased preference for larger-later rewards. • Exposure to immediate rewards decreased preference for larger-later rewards. • Changes in timing precision were not predictive of changes in choice. • More research is necessary to uncover the underlying mechanism for these effects. Abstract A relatively strong preference for smaller-sooner rewards (SSR) over larger-later rewards (LLR) is associated with a host of maladaptive behavioral patterns. As such, the clinical implications for increasing preference for LLR are profound. There is a growing body of literature that suggests extended exposure to delayed reward may increase preference for LLR in rats. However, questions remain about the underlying mechanism driving this effect and the extent to which extended exposure to immediate rewards may decrease LLR choice. In Experiment 1, we tested effects of a differential-reinforcement-of-low-rates schedule (DRL) to increase LLR choice using a pretest/posttest design with Wistar rats as subjects. We compared this group to a group of rats exposed to a differential-reinforcement-of-high-rates schedule (DRH). The DRH intervention has never been employed in this research context, but explicitly programs an immediate response-reinforcement requirement. In Experiment 2, we tested effects of an intervention with a delay longer than those used in the delay discounting pretest and posttest. No previous research has tested effects of an intervention delay this long, relative to the delay discounting task. We compared this group to a group exposed to a delay that was part of the delay discounting pretest and posttest and to a group exposed to a traditional no-delay, fixed-ratio (FR) 2 control intervention. In both experiments, we found that exposure to delayed rewards in the intervention phase significantly increased LLR choice relative to pretest performance. These findings replicate and extend a growing body of literature showing that delay exposure increases preference for LLR. We also found significant decreases in LLR choice from pretest to posttest in the DRH and no-delay intervention groups in Experiments 1 and 2, respectively. This is the first report of such an effect and has implications for understanding and interpreting effects of delay exposure training in past and future research. Our results also suggested no relationship between improved temporal tracking of reward and increases in LLR choice as a result of delay exposure training. [ABSTRACT FROM AUTHOR]

Verbal rules or instructions often exert obvious and meaningful control over human behavior. Sometimes instructions benefit the individual by enabling faster acquisition of a skill or by obviating an aversive consequence. However, research has also suggested a clear disadvantage: 'insensitivity' to changing underlying contingencies. The two experiments described here investigated the variables that control initial rule-following behavior and rule-following insensitivity. When the initial rule was inaccurate, behavior was consistent with the rule for approximately half of participants and all participants' behavior was mostly insensitive to changing contingencies. When the initial rule was accurate, behavior of all participants was consistent with it and behavior for nearly all participants was insensitive to changes in underlying contingencies. These findings have implications for how best to establish and maintain rule-following behavior in applied settings when deviant behavior would be more reinforcing to the individual. [ABSTRACT FROM AUTHOR]

The spontaneously hypertensive (SHR/NCrl) rat from Charles River is one of the most widely used models of the combined subtype of Attention-Deficit/Hyperactivity Disorder (ADHD-C). Although often used as its control strain, the Wistar Kyoto (WKY/NCrl) from Charles River has been proposed as a model of the predominately inattentive subtype of ADHD (ADHD-PI). In Experiment 1 SHR/NCrl, WKY/NCrl, and Wistar (WI; the progenitor strain for the two models) rats were trained on a left → right lever-press sequence in the presence of light discriminative stimuli that signaled the active lever in the sequence. In subsequent conditions the discriminative light cues were removed or reversed. WKY/NCrl accuracy remained relatively stable across cue light transitions. SHR/NCrl and WI accuracy was more disrupted when light cues were removed or reversed—an indication that behavior of the WKY/NCrl rats may not have come under control of the discriminative light cues as it did for the other strains, but relied more on past behavior and spatial cues. In Experiment 2, all three strains were exposed to a response-initiated fixed-interval (RIFI) 8-s schedule of reinforcement. In RIFI schedules behavior must be timed from a past instance of the target response. Replicating previous work, timing during the FI was roughly equivalent across the three strains; however, latencies to initiate the FI were significantly longer for SHR/NCrl than WKY/NCrl and WI rats, suggesting SHR/NCrl behavior was less sensitive to the first-response:food contingency in the RIFI schedule. These findings identify differences in stimulus control between the three strains and may help determine the efficacy of SHR/NCrl and WKY/NCrl as models of ADHD subtypes in humans. [ABSTRACT FROM AUTHOR]

Behavior and events distributed in time can serve as markers that signal delays to future events. The majority of timing research has focused on how behavior changes as the time to some event, usually food availability, decreases. The primary objective of the two experiments presented here was to assess how behavior changes as time passes between two time markers when the first time marker was manipulated but the second, food delivery, was held constant. Pigeons were exposed to fixed-interval, response-initiated fixed-interval, and signaled response-initiated fixed-interval 15- and 30-s schedules of reinforcement. In Experiment 1, first-response latencies were systematically shorter in the signaled response-initiated schedules than response-initiated schedules, suggesting that the first response was a more effective time marker when it was signaled. In Experiment 2, responding in no-food (i.e. 'peak') trials indicated that timing accuracy was equivalent in the three schedule types. Compared to fixed interval schedules, timing precision was reduced in the signaled response-initiated schedules and was lowest in response-initiated schedules. Results from Experiments 1 and 2 coupled with previous research suggest that the overall 'informativeness' of a time marker relative to other events and behaviors in the environment may determine its efficacy. [ABSTRACT FROM AUTHOR]

Aversive control is a common method to reduce undesirable behavior in horses. However, it often results in unintended negative side effects, including potential abuse of the animal. Procedures based on positive reinforcement, such as differential reinforcement of other behavior (DRO), may reduce undesirable behaviors with fewer negative consequences. The current study used DRO schedules to reduce pawing using a multiple baseline design across 3 horses. Results indicated that DRO schedules were effective at reducing pawing. However, individual differences in sensitivity to DRO and reinforcer efficacy may be important considerations. [ABSTRACT FROM AUTHOR]

Different events can serve as time markers that initiate intervals in schedules of reinforcement. Pigeons were exposed to fixed-interval (FI) schedules in which the onset of the interval was signaled by the illumination of a key light or initiated by a peck to a lighted key. Food was delivered following the first response after the interval elapsed. In Experiment 1, three pigeons were exposed to a multiple schedule. One component was a standard FI schedule: Key light illumination signaled the onset of the interval. The other component was a response-initiated fixed-interval (RIFI) schedule: The first key-peck response determined the onset of the interval. In Experiment 2, three pigeons were exposed to a multiple FI-RIFI schedule of reinforcement and on occasional trials food was not delivered (i.e. "no-food" or "peak trials"). A yoking procedure equated reinforcement rates between the schedule types in both experiments. Absolute response rates early in the intervals were higher in the RIFI schedules of both experiments. Normalized response-rate gradients, ogive fits of normalized response gradients, and breakpoints were not systematically different for the schedule types in Experiment 1, indicating similar patterns of responding between interval onset and food delivery. However, during peak trials in Experiment 2 the duration of responding at a high rate was longer for RIFI schedules than FI schedules. This suggests that timing precision was reduced in the RIFI schedules and that relative "distinctiveness" of a time marker may determine its efficacy. [ABSTRACT FROM AUTHOR]

Models of interval timing typically include a response threshold to account for temporal production. The present study sought to evaluate the dependent concurrent fixed-interval fixed-interval schedule of reinforcement as a tool for selectively isolating the response threshold in rats, pigeons, and humans. In this task, reinforcement is available either at one location after a short delay or at another location at a longer delay. Because the reinforced location is not signaled, subjects normally respond on the first location and, if reinforcement is not delivered, then switch to the second location. The latency to switch between locations served as the primary dependent measure. After training rats, pigeons, and humans with equal reinforcement magnitudes in the short and long delays, the magnitude of reinforcement was increased threefold on the long-delay location. Consistent with model predictions, this biasing procedure decreased estimates of the response threshold of rats and pigeons, but also reduced temporal control in these species and increased response-threshold estimates in humans. Human and pigeon performance also suggested a magnitude-induced increase in the speed of the internal clock. Collectively, these results suggest that differences in reinforcement magnitude between response alternatives appear to modulate the response threshold, but not selectively, and may provide guidance for better isolating response-threshold effects in humans. [ABSTRACT FROM AUTHOR]

State-dependent valuation learning (SDVL) is a preference for stimuli associated with relative food deprivation over stimuli associated with relative satiety. Pigeons were exposed to experimental conditions designed to investigate SDVL and to test the hypothesis that obtained relative immediacy during training predicts choice during test probes. Energy states were manipulated using a procedure that has previously revealed SDVL in starlings and pigeons. In Experiment 1, pigeons preferred the stimulus associated with deprivation in the first choice probe session, but were indifferent in the second. Changes in choice were consistent with changes in obtained relative immediacy. In Experiment 2, training parameters were altered and SDVL did not occur. Obtained relative immediacy again predicted choice. Results of both experiments provide evidence that obtained relative immediacy may be an important contributing factor to the SDVL phenomenon. [ABSTRACT FROM AUTHOR]

In fixed-interval (FI) and response-initiated fixed-interval (RIFI) schedules of reinforcement, a response is required after an interval has elapsed for delivery of reinforcement. In RIFI schedules, a response is required to initiate each interval as well. The objective of this experiment was a systematic comparison of performance in the two schedule types over a range of interval durations. Four pigeons were exposed to FI and RIFI schedules of 15, 30, 60, 120 and 240 s. Interfood intervals were longer and more variable in RIFI than corresponding FI schedules. In addition, response rates early in the RIFI schedules were higher than in corresponding FI schedules. However, the distribution of first-response latencies, mean breakpoints, and normalized response gradients suggest that temporal discrimination was equivalent in the two schedules. [ABSTRACT FROM AUTHOR]

The present study investigated the effects of punishing responses inconsistent with rules on instructional control during a choice task. In a procedure modeled after Hackenberg and Joker (1994), 7 adults were presented with repeated choices between progressive- and fixed-time schedules of reinforcement and were given instructions (rules) for how to respond to maximize earnings. Across sessions, the progressive-time schedule step size was manipulated so that the instructions became increasingly inaccurate, and deviating from the instructions produced greater earnings. The experiment consisted of two phases, Penalty and No Penalty. During the Penalty phase, deviating from the instructions produced a money-loss penalty (response-cost punishment). Two participants showed persistent instructional control and therefore completed only one phase (Penalty or No Penalty), and 1 participant showed little instructional control during the Penalty phase until the punishment magnitude was increased. In all 4 participants who experienced both Penalty and No Penalty phases, punishment increased the consistency of choices with the instructions, and in 2 of these participants punishment increased the progressive-schedule step size at which choices began to systematically deviate from the instructions. These results show that monetary penalties for breaking with rules may enhance instructional control, but that deviations from rules still occur under punishment when such deviations produce greater reinforcement than rule following. [ABSTRACT FROM AUTHOR]

Abstract: Biting and chewing by horses on crossties can result in injury to the handler and damage to equipment. Operant-conditioning techniques have been used to train horses and could be used to reduce or eliminate undesirable biting and chewing. Presently, a differential-reinforcement-of-other-behavior (DRO) schedule, in the context of a reversal design, was effective in reducing biting and chewing in two horses. In DRO schedules, a reinforcer is delivered contingent on the absence of a target behavior for a specified interval. Positive-reinforcement procedures offer an alternative to aversive-control techniques typically used in equine training and may provide for better equine welfare and horse–human interaction. [Copyright &y& Elsevier]

• The CNTNAP2 gene is implicated in several neuropsychological disorders. • CNTNAP2 knockout rats and controls were compared on a temporal bisection task. • CNTNAP2 knockout rats exhibited less precise timing at the long cue durations. • Results have implications for understanding role of CNTNAP2 gene in timing. The CNTNAP2 gene has been implicated in several neuropsychological disorders, including autism spectrum disorder (ASD) and schizophrenia. The CNTNAP2 knockout (KO) rat model, rats without the CNTNAP2 gene, exhibits deficits in social interaction and increases in both repetitive and anxiety-like behaviors. However, deficits in time perception that may underlie several of the neuropsychological disorders implicated have not been investigated. The current study investigated timing in CNTNAP2 KO rats compared to control rats using a discrete-trial temporal bisection task. Results suggested deficits in the timing of relatively long durations in the CNTNAP2 KO rats. This finding is consistent with similar findings previously reported in humans diagnosed with ASD, and is promising for understanding the role that the CNTNAP2 gene may play in timing in certain neuropsychological disorders, and for developing targeted clinical therapies. [ABSTRACT FROM AUTHOR]