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Reversal learning has been studied in many species, often as an indicator of their behavioral flexibility. Although this research typically focuses on individuals, groups of social animals, especially social insects, are often considered to have similar learning capabilities. Associative learning has been rarely studied in ant colonies and their behavioral flexibility is still to be assessed. In this study, ant colonies readily learned to discriminate between compound visuotactile cues and subsequently learned their reversal. Reversal performance was maintained after a 5-day retention interval, but not after a 10-day interval. Although this study does not differentiate learning processes at the individual vs. colony levels, it is the first demonstration of reversal learning conducted in ant colonies. These results show that the two-corridor maze can serve to assess colony-level learning in ants. This is a first step to investigate key mechanisms underlying collective learning and cognition in ants.

The distribution of foraging strategies and associated activities of Wistar rats was examined, with food outcomes presented in small vs. large units. Groups of 4 rats foraged for food in a 4 x 3 array of covered holes, some containing 4 g of food. For some groups, food consisted of shelled sunflower seeds (small units); for other groups, food consisted of 3 pellets of chow (large units). Foraging strategies were classified as either production (seeking patches with food) or scrounging (tracking conspecifics). Production strategies were more common among groups that foraged for pellets instead of seeds. Producing food was highly correlated with contacting gates covering holes, whereas scrounging for food was highly correlated with following others in the group. The prevalence of activities associated with each foraging strategy was highly correlated with the proportion of time spent consuming food obtained from each activity (i.e., produced vs. scrounged food). Taken together, these findings suggest that, similar to other species, the finder’s advantage (low with small units, high with large units) modulates social foraging strategies in rats. A simple outcome-strategy feedback mechanism appears to mediate this modulation.

Chronic stress typically leads to deficits in fear extinction when tested soon after chronic stress ends. Given the importance of extinction in updating fear memories, the current study examined whether fear extinction was impaired in rats that were chronically stressed and then given a break from the end of chronic stress to the start of fear conditioning and extinction. Male rats were chronically stressed by restraint (6 h/d/21 d) and tested soon (termed immediate, STR-IMM), or 3 or 6 wk after a rest period from restraint (termed rest or "R," STR-R3, STR-R6). In Experiment 1, STR-R3 and STR-R6 discriminated between the cue and nonshock context better than STR-IMM or control. Interestingly, STR-IMM showed high freezing to the nonshock context. Consequently, Experiment 2 investigated whether STR-IMM generalized across contexts, which was not supported. Experiment 3 determined whether STR-IMM were susceptible to second-order conditioning to a novel context, but showed that the level of second-order conditioning was similar for all groups. These findings reveal that rats exposed to chronic stress and then given a rest period of 3 or 6 wk, express unique fear extinction profiles compared to control and STR-IMM. Specifically, STR-R demonstrated excellent cue and context discrimination during extinction, and perhaps showed a stress inoculation effect. For STR-IMM, the heightened freezing under these extensive acclimation parameters was not attributed to generalization nor to second-order fear conditioning to "safe" contexts and, instead, may reflect hypervigilance.

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.

The game of Matching Pennies (MP), a simplified version of the more popular Rock, Papers, Scissors, schematically represents competitions between organisms with incentives to predict each other's behavior. Optimal performance in iterated MP competitions involves the production of random choice patterns and the detection of nonrandomness in the opponent's choices. The purpose of this study was to replicate systematic deviations from optimal choice observed in humans when playing MP, and to establish whether suboptimal performance was better described by a modified linear learning model or by a more cognitively sophisticated reinforcement-tracking model. Two pairs of pigeons played iterated MP competitions; payoffs for successful choices (e.g., "Rock" vs. "Scissors") varied within experimental sessions and across experimental conditions, and were signaled by visual stimuli. Pigeons' behavior adjusted to payoff matrices; divergences from optimal play were analogous to those usually demonstrated by humans, except for the tendency of pigeons to persist on prior choices. Suboptimal play was well characterized by a linear learning model of the kind widely used to describe human performance. This linear learning model may thus serve as default account of competitive performance against which the imputation of cognitively sophisticated processes can be evaluated. (Contains 3 tables, 6 figures, and 2 footnotes.)

Despite being under challenge for the past 50 years, null hypothesis significance testing (NHST) remains dominant in the scientific field for want of viable alternatives. NHST, along with its significance level "p," is inadequate for most of the uses to which it is put, a flaw that is of particular interest to educational practitioners who too often must use it to sanctify their research. In this article, we review the failure of NHST and propose "p[subscript rep]," the probability of replicating an effect, as a more useful statistic for evaluating research and aiding practical decision making. (Contains 2 tables and 2 figures.)

Twelve pigeons were exposed to negative automaintenance contingencies for 17-27 sessions immediately after brief (14-16 sessions) or extended (168-237 sessions) exposure to positive automaintenance contingencies, or after 4-10 sessions of instrumental training. In all conditions, negative automaintenance contingencies virtually eliminated responding, reducing response rates to an average 1.3 responses per min. This reduction in response rate was validated by a model of transition between early and late response rates that assumed exponential transition of rates from one set of contingencies to the next. The model faithfully reproduced cumulative records, and yielded estimates of terminal rates under negative automaintenance that were close to operant level. (Contains 3 tables, 2 footnotes and 3 figures.)

Pigeons responded to intermittently reinforced classical conditioning trials with erratic bouts of responding to the conditioned stimulus. Responding depended on whether the prior trial contained a peck, food, or both. A linear persistence-learning model moved pigeons into and out of a response state, and a Weibull distribution for number of within-trial responses governed in-state pecking. Variations of trial and intertrial durations caused correlated changes in rate and probability of responding and in model parameters. A novel prediction--in the protracted absence of food, response rates can plateau above zero--was validated. The model predicted smooth acquisition functions when instantiated with the probability of food but a more accurate jagged learning curve when instantiated with trial-to-trial records of reinforcement. The Skinnerian parameter was dominant only when food could be accelerated or delayed by pecking. These experiments provide a framework for trial-by-trial accounts of conditioning and extinction that increases the information available from the data, permitting such accounts to comment more definitively on complex contemporary models of momentum and conditioning. Keywords: autoshaping, behavioral momentum, classical conditioning, dynamic analyses, instrumental conditioning DOI: 10.1037/a0015626