Tuning the developing brain to emotional body expressions

Reading others' emotional body expressions is an essential social skill. Adults readily recognize emotions from body movements. However, it is unclear when in development infants become sensitive to bodily expressed emotions. We examined event‐related brain potentials (ERPs) in 4‐ and 8‐month‐old infants in response to point‐light displays (PLDs) of happy and fearful body expressions presented in two orientations (upright and inverted). The ERP results revealed that 8‐month‐olds but not 4‐month‐olds respond sensitively to the orientation and the emotion of the dynamic expressions. Specifically, 8‐month‐olds showed (i) an early (200–400 ms) orientation‐sensitive positivity over frontal and central electrodes, and (ii) a late (700–1100 ms) emotion‐sensitive positivity over temporal and parietal electrodes in the right hemisphere. These findings suggest that orientation‐sensitive and emotion‐sensitive brain processes, distinct in timing and topography, develop between 4 and 8 months of age.     

Motivational control of instrumental performance: The role of prior experience of the reinforcer

In four experiments we investigated the conditions that are necessary for instrumental performance to adjust appropriately to a change in drive state. Rats were trained to press a lever and pull a chain concurrently, with one action being reinforced by sucrose solution and the other by food pellets. In Experiment 1 for animals that were hungry throughout training the rate of lever pressing in an extinction test under thirst was unaffected by the type of reinforcer produced by this action during training, even though the sucrose solution would maintain a higher rate than the food pellets during training under thirst. In contrast, animals that experienced the instrumental contingencies arranged by the concurrent schedule while thirsty at some point during training pressed the lever more during the extinction test under thirst when this action had been reinforced with the sucrose solution rather than the food pellets. The remaining three experiments demonstrated that for this incentive effect to occur it is sufficient that the sucrose solution be delivered non-contingently under thirst at some stage of training. Thus, it would appear that performance mediated by an instrumental contingency adjusts appropriately to reinforcer revaluation brought about by a drive shift only if the animals have had prior experience with the incentive under the test drive state. This observation was interpreted in terms of Tolman's “cathexis” theory of motivation.     

The Benefit of Forgetting Suicidal Ideation

In a sample of young adult Australians, those who had had suicidal ideation but who did not acknowledge ever having had it when asked 4 years later, were experiencing better mental health, as demonstrated by significantly better functioning on a range of psychometric measures, than those who recalled it. These results are consistent with several recent reports and indicate that forgetting painful events such as suicidal ideation is an adaptive defense mechanism. This has implications in terms of therapy focusing on contemporaneous events and the future, rather than on the past.     

The control response in assessing resurgence: Useful or compromised tool?

Resurgence experiments sometimes include an operandum on which a history of reinforcement has not been experimentally established. The purpose of this control operandum is to rule out a generalized increase in responding when the alternative response is extinguished as being the cause of the resurgent target response. A review of the results of experiments conducted with both nonhumans and humans in which a control operandum was included shows that control- operandum responding is more common in the latter and almost nonexistent in the former. Both the presence and absence of responding on the control operandum, however, are subject to multiple interpretations thereby rendering it a compromised tool. Alternatives to using a control operandum to rule out extinction induction as the basis for resurgence include a preresurgence test control procedure and a differential resurgence procedure.