Conflicts between priming and episodic retrieval: a question of fluency?

Human memory consists of different underlying processes whose interaction can result in counterintuitive findings. One phenomenon that relies on various types of mnemonic processes is the repetition priming effect for unfamiliar target faces in familiarity decisions, which is highly variable and may even reverse. Here, we tested the hypothesis that this reversed priming effect may be due to a conflict between target fluency signals and episodic retrieval processes. After replicating the reverse priming effect, three different manipulations were effective in diminishing it. We suggest that each of these manipulations diminished the ambiguity regarding the source of priming-induced fluency of target processing. Our findings argue against a strictly independent view of different types of memory.

Deliberate control over facial expressions in motherhood. Evidence from a Stroop-like task.

The deliberate control of facial expressions is an important ability in human interactions, in particular for mothers with prelinguistic infants. Because research on this topic is still scarce, we investigated the control over facial expressions in a Stroop-like paradigm. Mothers of 2-6 months old infants and nullipara women produced smiles and frowns in response to verbal commands written on distractor faces of adults or infants showing expressions of happiness or anger/distress. Analyses of video recordings with a machine classifier for facial expression revealed pronounced effects of congruency between the expressions required by the participants and those displayed by the face stimuli on the onset latencies of the deliberate facial expressions. With adult distractor faces this Stroop effect was similar whether participants smiled or frowned. With infant distractor faces mothers and non-mothers showed indistinguishable Stroop effects on smile responses; however, for frown responses, the Stroop effect in mothers was smaller than in non-mothers. We suggest that for frown responses in mothers when facing infants, the effect of mimicry or stimulus response compatibility, leading to the Stroop effect, is offset by a caregiving response or empathy.

COMT genotype is differentially associated with single trial variability of ERPs as a function of memory type.

Previous research on the association between intra-subject variability (ISV) in reaction times (RTs) and the Val158Met polymorphism of the catechol-o-methyltransferase gene (COMT; rs4680) has yielded mixed results. The present study compared the associations between COMT genotype and ISV in P3b latency measured during working and secondary memory tasks using residue iteration decomposition (RIDE) of single trial latencies. We compared the outcome of the present analyses with a previous analysis of the same data (N=70, n-back tasks) using an alternative single-trial method. Additionally, we used RIDE to analyse the association between COMT genotype and ISV in an independent sample performing a different task (N=91, face-recognition task). Analyses reconfirmed previous results from the n-back tasks, showing that Val alleles are associated with lower ISV. In the face recognition tasks, genotype interacted with task conditions, so Val homozygotes had higher ISV to unfamiliar faces than familiar ones but Met carriers showed no effect of familiarity. Moreover, in both datasets trial-by-trial RTs were predicted by P3b latencies. Therefore, the present data suggests that associations between COMT genotype and ISV depend on the type of cognitive processes, which may explain heterogeneity in previous results.