Aftereffects of the surprising presentation and omission of appetitive reinforcers on key-pecking performance in pigeons

The reinforcement-omission effect (ROE), also known as frustration effect, refers to greater response strength immediately after nonreinforcement (N) than reinforcement (R). The ROE was traditionally interpreted as transient invigoration after N induced by primary frustration. Pigeons demonstrate similar ROEs whether outcomes are surprising (partial R) or expected (discrimination training) in runway (Experiment 1) and Skinner box situations (Experiments 2-3). Variations in the interval between N and the opportunity to respond indicate that the ROE results from an aftereffect of food consumption (Experiment 4). Increasing reinforcer magnitude increased the after-R effect, without modifying the after-N function (Experiment 5). These results are reviewed in the context of comparative research on spaced-trial successive negative contrast and related phenomena that have failed to appear in experiments involving nonmammalian vertebrates.     

Peripheral pain enhances the effects of incentive downshifts

Physical pain (induced by tissue damage) and psychological pain (induced by surprising incentive loss) share a set of common neural substrates, but little is known about their interactions. The present research studied such interactions using the formalin test to induce physical pain and consummatory successive negative contrast (cSNC) to induce psychological pain. In the formalin test, animals receive an intradermal injection of formalin (1%) in a hind paw. In cSNC, rats with free access to 32% sucrose show a sharp suppression of drinking behavior after a downshift to 4% sucrose, compared to rats that always receive 4% sucrose. In Experiment 1, formalin administration before the first and second 32-to-4% sucrose downshift trials enhanced cSNC. In Experiment 2, a similar treatment before the first downshift trial after a 16-to-4% sucrose downshift, which normally produces little or no evidence of cSNC, significantly increased cSNC. In Experiment 3, using a 32-to-4% sucrose downshift procedure similar to that of Experiment 1, no effects were observed following formalin administration immediately after Trial 11. Thus, no evidence was found that the effects of physical pain on cSNC were caused by changes in memory consolidation. The procedures used in these experiments offer a new approach to study the neural substrates of interactions between physical and psychological pain.     

Effect of cognitive bias modification-memory on depressive symptoms and autobiographical memory bias: two independent studies in high-ruminating and dysphoric samples

Memory bias is a risk factor for depression. In two independent studies, the efficacy of one CBM-Memory session on negative memory bias and depressive symptoms was tested in vulnerable samples. We compared positive to neutral (control) CBM-Memory trainings in highly-ruminating individuals (N?=?101) and individuals with elevated depressive symptoms (N?=?100). In both studies, participants studied positive, neutral, and negative Swahili words paired with their translations. In five study–test blocks, they were then prompted to retrieve either only the positive or neutral translations. Immediately following the training and one week later, we tested cued recall of all translations and autobiographical memory bias; and also measured mood, depressive symptoms, and rumination. Retrieval practice resulted in training-congruent recall both immediately after and one week after the training. Overall, there was no differential decrease in symptoms or difference in autobiographical memory bias between the training conditions. In the dysphoric but not in the high-ruminating sample, the positive training resulted in positive autobiographical bias only in dysphoric individuals with positive pre-existing bias.

We conclude that one session of positive retrieval-based CBM-Memory may not be enough to yield symptom change and affect autobiographical memory bias in vulnerable individuals.     

Evidence of successive negative contrast in terrestrial toads (Rhinella arenarum): central or peripheral effect?

Animal Cognition - Prior research with terrestrial toads (Rhinella arenarum) in a water-reinforced instrumental situation indicated a direct relationship between acquisition rate and reward...     

Massed trial Overtraining Effects on Extinction and Reversal Performance in Turtles (Geoclemys reevesii)

Two experiments with turtles (Geoclemys reevesii) examined the overtraining extinction effect (OEE) and the overtraining reversal effect (ORE), under massed training conditions. In Experiment 1, three groups of turtles received 7, 14, or 21 sessions of training in a runway situation for food reinforcement, followed by 15 sessions of extinction. Extinction was faster, the greater the number of acquisition sessions. In Experiment 2, the two groups of turtles learned a spatial discrimination for food reinforcement either to a criterion (19 of 20 correct responses), or to that criterion plus 100 additional trials of overtraining. When the validity of the positions was reversed, learning was faster for the overtrained group than for the group trained to a criterion. This evidence of the OEE and the ORE is the first yet reported for a reptile. The results are discussed in the framework of comparative research on rewardschedule effects.