Personality, cardiovascular, and cortisol reactions to acute psychological stress in the Midlife in the United States (MIDUS) study.

Recent research has suggested that diminished, as well as elevated reactivity to acute psychological stress is maladaptive. These differences in stress reactions have been hypothesized to relate to the Big Five personality traits, which are said to be biologically-based and stable across adulthood; however, findings have been inconclusive. This study sought to replicate the findings of the largest study conducted to date (Bibbey et al., 2013), with a sample of participants from the Midlife in the United States Study (MIDUS), aged between 35 and 84 years (M = 56.33, SD = 10.87). Participants (N = 817) undertook a standardized, laboratory-based procedure during which their cardiovascular and neuroendocrine reactivity to acute stress was measured. In contrast to Bibbey et al. (2013), associations between neuroticism and blunted reactivity did not withstand adjustment for confounding variables. Further, following adjustment for multiple tests, no significant positive association between agreeableness and HR reactivity was observed. Methodological differences between the studies, which may account in part for the contrasting findings, are discussed. Further conceptual replication research is needed to clarify associations between the Big Five personality traits and stress reactivity, across the lifespan.

Learning efficiency: The influence of cue salience during spatial navigation.

In three experiments, male Wistar rats were trained to find a hidden platform in the Morris water maze using two cues for five or ten days. Experiments 1 and 2 investigated two factors of cue salience; proximity to the goal and brightness. Results from Experiment 1 showed that rats tested with a bright distal cue were significantly better at locating the platform than rats tested with the proximal cue after five- and ten-day training with both cues. In Experiment 2, the position of the cues was reversed. Rats tested with a brighter proximal cue outperformed those tested with a distal cue. Findings from Experiments 1 and 2 suggest that brightness acquired more control over rats' behaviour than proximity to the goal. Animals in Experiment 3 were trained with equally bright proximal and distal cues. Unexpectedly, probe tests revealed that rats tested with the farther cue were more accurate than those tested with the proximal cue, but only after extended training. Possible explanations for this result are discussed with reference to errors in directional information estimation and cue assignment, cue elevation and the use of the pool wall as a navigational aid. Taken together, findings point towards the use of an elemental learning strategy involving the more salient of the two cues which emerged earlier when the relative saliences of the cues differed considerably.