Evidence accumulation in the integrated and primed Stroop tasks

We report distributional analyses of response times (RT) in two variants of the color-word Stroop task using manual keypress responses. In the classic Stroop task, in which the color and word dimensions are integrated into a single stimulus, the Stroop congruence effect increased across the quantiles. In contrast, in the primed Stroop task, in which the distractor word is presented ahead of colored symbols, the Stroop congruence effect was manifested solely as a distributional shift, remaining constant across the quantiles. The distributional-shift pattern mirrors the semantic-priming effect that has been reported in semantic categorization tasks. The results are interpreted within the framework of evidence accumulation, and implications for the roles of task conflict and informational conflict are discussed.     

Effects of body mass index and education on verbal and nonverbal memory

We previously reported that higher education protects against executive dysfunction related to higher body mass index (BMI) in younger, but not older, adults. We now extend the previous analyses to verbal and nonverbal memory. Fifty-nine healthy, dementia-free community-dwelling adults ranging in age from 18 to 81 years completed the Hopkins Verbal Learning Test – Revised (HVLT-R) and the Brief Visuospatial Memory Test – Revised (BVMT-R). Self-reported years of education served as a proxy for cognitive reserve. We found that more highly educated individuals maintained their BVMT-R immediate recall performance across the range of BMI, but in less educated individuals, higher BMI was associated with worse performance. Our findings suggest that education may play a protective role against BMI-related nonverbal learning deficits, similar to previous reports for verbal memory and executive functioning. Results highlight the importance of considering educational background when determining the risk for BMI-related cognitive impairment in clinical settings.     

Impaired acquisition of goal-directed action in healthy aging

According to dual-system theories, instrumental learning is supported by dissociable goal-directed and habitual systems. Previous investigations of the dual-system balance in healthy aging have yielded mixed results. To further investigate this issue, we compared performance of young (17–24 years) and older (69–84 years) adults on an instrumental learning task. Following the initial learning phase, the behavioral autonomy of the motivational significance of the instrumental outcome was assessed with an outcome-devaluation test and slips-of-action test. The present study provides evidence for a disrupted dual-system balance in healthy aging, as reflected in reduced outcome-induced conflict during acquisition, as well as in impaired performance during the test stage, during which participants had to flexibly adjust their actions to changes in the current desirability of the behavioral outcome. These findings will be discussed in relation to previous aging studies into habitual and goal-directed control, as well as other cognitive impairments, challenges that older adults may face in everyday life, and to the neurobiological basis of the developmental pattern of goal-directed action across the lifespan.     

The interaction between discriminative stimuli and outcomes during instrumental learning

Rats were trained on a biconditional discrimination in which the delivery of a food pellet stimulus signalled that pressing on one of two levers would be reinforced, whereas the delivery of a sucrose solution stimulus signalled that the reward was contingent on pressing the other lever. The outcome was the same food type as the discriminative stimulus in the congruent group but the other food type in the incongruent group. Both responses were rewarded with the same outcome in the same group. All the three groups learned the discrimination at statistically indistinguishable rates. Prefeeding one of the outcomes selectively reduced the associated response thereby demonstrating that responding was mediated by a representation of the outcome. Moreover, the outcome of one trial controlled responding on the next trial in accord with the stimulus function of the food type. These results are discussed in relation to the associative structures mediating the discriminative control of instrumental performance.     

Very pre‐term infants' behaviour at 1 and 2 years of age and parental stress following basic developmental care

This study explored the effects of basic developmental care on the behaviour of very pre‐term infants and parental stress at 1 and 2 years of corrected age. A randomized controlled trial was done to compare basic Developmental Care (standardized nests and incubator covers) and controls (standard care). Parents of infants born <32 weeks of gestation completed questionnaires measuring child behaviour and parental stress at 1 year (N = 139) and 2 years (N = 133) of the child's age. Parental stress was measured using the Nijmegen Parenting Stress Index and child behaviour was measured using the Infant–Toddler Social and Emotional Assessment (ITSEA) and the Child Behaviour Checklist 2–3. At 1 year of age, children in the basic developmental care group had significantly higher behaviour scores on the total competence domain (p = .009) and the competence subscale mastery motivation (p = .002) of the ITSEA questionnaire, meaning that the infants showed more curiosity, persistence, obedience and enjoyment with small accomplishments. No significant effects were found on problem behaviour or parenting stress. We conclude that introducing a basic form of developmental care in the neonatal intensive care unit has a positive influence on the child's competence behaviour at 1 year of age.