Stress-related immune changes in middle-aged and older women: 1-year consistency of individual differences.

This study reviews prior research and reports longer-term consistency of stress-related immune variables in middle-aged and older women who performed mental math and speech tasks 2 times 1 year apart. Leukocyte subsets, mitogen-induced lymphocyte proliferation, and natural killer cell activity were measured at baseline, after tasks, and after 30-min recovery. Epstein-Barr virus (EBV) antibody titers were assessed at baseline. Pearson coefficients and standardized maximum-likelihood estimates of year-to-year covariances for leukocyte subsets and EBV titers showed moderately high to high baseline and posttask consistency and lower recovery consistency; consistency for other functional immune assays and reactivity scores for all variables was moderate to low. Results support longitudinal study of psychosocial context effects on tonic immune function and posttask scores.     

Choice between delayed reinforcers in an adjusting-delay schedule: The effects of absolute reinforcer size and deprivation level

Choice between two reinforcers differing in magnitude and delay was investigated in rats using an adjusting-delay discrete-trials schedule in which the two reinforcers were associated with two levers (A and B). The delay to Reinforcer A (the smaller reinforcer) was always 2 sec, whereas the delay to Reinforcer B was varied in accordance with the distribution of choices in successive blocks of trials. In Experiment 1, the mean delay to the large reinforcer during the last 5 of 60 training sessions was greater when the rats were maintained at 80% than when they were maintained at 90% of their free-feeding body weights. In Experiment 2, the delay to the larger reinforcer was greater when the two reinforcers consisted of one and two 45-mg food pellets than when they consisted of three and six pellets. The results are consistent with a model of “self-control” which posits hyperbolic relations between reinforcer value and reinforcer magnitude, and between reinforcer value and delay of reinforcement.     

Space and movement in working memory

Encoding seen movement of another human body requires visuo-spatial processing, and recall involves motor activity. However, encoding whole body movement patterns is affected differently by patterned and spatial secondary tasks, and this difference is reversed for encoding of spatial targets for movement (Smyth, Pearson, & Pendleton, 1988). The experiments reported here investigate the rehearsal of such movement patterns and their recall over unfilled and filled intervals. Performing, watching, or encoding a sequence of spatial positions while carrying a memory load of movement patterns did not affect recall of those movements, whereas performing, watching, or encoding a further set of patterned movements reduced the number recalled from the original set. However, memory for a series of locations in space was not affected by watching patterned movements during the interval, and only order information was affected by watching movement to a series of spatial locations during the interval. The results are discussed in terms of the independence of rehearsal mechanisms for spatial sequencing and movement patterns.