Rats responded on concurrent schedules of shock-postponement or deletion (avoidance) and timeout from avoidance. In Experiment 1, 3 rats' responses on one lever postponed shocks for 20 s and responses on a second lever produced a 1-min timeout according to a variable-interval 45-s schedule. Across conditions, a warning signal (white noise) was…

Although response-dependent shock often suppresses responding, response facilitation can occur. In two experiments, we examined the suppressive and facilitative effects of shock by manipulating shock intensity and the interresponse times that produced shock. Rats' lever presses were reinforced on a variable-interval 40-s schedule of food…

Previous research suggested that allocation of responses on concurrent schedules of wheel-running reinforcement was less sensitive to schedule differences than typically observed with more conventional reinforcers. To assess this possibility, 16 female Long Evans rats were exposed to concurrent FR FR schedules of reinforcement and the schedule…

Twelve rats made repeated choices on an adjusting-delay schedule between a smaller reinforcer (A) that was delivered immediately after a response and a larger reinforcer (B) that was delivered after a delay which increased or decreased by 20% depending on the subject's choices in successive blocks of trials. In two phases of the experiment (100…

In a temporal double bisection task, animals learn two discriminations. In the presence of Red and Green keys, responses to Red are reinforced after 1-s samples and responses to Green are reinforced after 4-s samples; in the presence of Blue and Yellow keys, responses to Blue are reinforced after 4-s samples and responses to Yellow are reinforced…

Pigeons trained on successive AB symbolic matching show emergent BA antisymmetry if they are also trained on successive AA oddity and BB identity (Urcuioli, 2008, Experiment 4). In other words, when tested on BA probe trials following training, they respond more to the comparisons on the reverse of the nonreinforced AB baseline trials than on the…

In Experiment 1, food-deprived rats responded to one of two schedules that were, with equal probability, associated with a sample lever. One schedule was always variable ratio, while the other schedule, depending on the trial within a session, was: (a) a variable-interval schedule; (b) a tandem variable-interval,…

When given to pigeons, the direct-acting dopamine agonist apomorphine elicits pecking. The response has been likened to foraging pecking because it bears remarkable similarity to foraging behavior, and it is enhanced by food deprivation. On the other hand, other data suggest the response is not related to foraging behavior and may even interfere…

The relationship between positive and negative reinforcement and the symmetry of Thorndike's law of effect are unresolved issues in operant psychology. Here we show that, for a given pattern of responding on variable interval (VI) schedules with the same programmed rate of food rewards (positive reinforcement VI) or electric shocks (negative…

Emerging evidence suggests that nicotine may enhance short-term memory. Some of this evidence comes from nonhuman primate research using a procedure called delayed matching-to-sample, wherein the monkey is trained to select a comparison stimulus that matches some physical property of a previously presented sample stimulus. Delays between sample…

In comparing open and closed economies, researchers often arrange shorter sessions under the former condition than under the latter. Several studies indicate that session length per se can affect performance and there are some data that indicate that this variable can influence demand functions. To provide further data, the present study exposed…

Conditioned reinforcer effects may be due to the stimulus' discriminative rather than its strengthening properties. While this was demonstrated in a frequently-changing choice procedure, a single attempt to replicate in a relatively static choice environment failed. We contend that this was because the information provided by the stimuli was…

It has long been understood that food deliveries may act as signals of future food location, and not only as strengtheners of prefood responding as the law of effect suggests. Recent research has taken this idea further--the main effect of food deliveries, or other "reinforcers", may be signaling rather than strengthening. The present experiment…

Previous reports using stimulus intensity changes to disrupt temporal discrimination have shown shifts in the psychophysical curve for time, while studies using other disruptors have shown a flattening of the curve. The current study investigated the impact of increases and decreases in stimulus intensity on temporal discrimination in pigeons, to…

The effectiveness of a fixed-ratio (FR) escalation procedure, developed by Pinkston and Branch (2004) and based on interresponse times (IRTs), was assessed during lever-press acquisition. Forty-nine experimentally naive adult male Long Evans rats were deprived of food for 24 hr prior to an extended acquisition session. Before the start of the…