The present review addresses the physiological correlates of planning effects on behavior. Although intentions to act qualify as predictors of behavior, accumulated evidence indicates that there is a substantial gap between even strong intentions and subsequent action. One effective strategy to reduce this intention–behavior gap is the formation of implementation intentions that specify when, where, and how to act on a given goal in an if-then format (“If I encounter situation Y, then I will initiate action Z!”). It has been proposed that implementation intentions render the mental representation of the situation highly accessible and establish a strong associative link between the mental representations of the situation and the action. These process assumptions have been examined in behavioral research, and in physiological research, a field that has begun to investigate the temporal dynamics of and brain areas involved in implementation intention effects. In the present review, we first summarize studies on the cognitive processes that are central to the strategic automation of action control by implementation intentions. We then examine studies involving critical samples with impaired self-regulation. Lastly, we review studies that have applied physiological measures such as heart rate, cortisol level, and eye movement, as well as electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) studies on the neural correlates of implementation intention effects. In support of the assumed processes, implementation intentions increased goal attainment in studies on cognitive processes and in critical samples, modulated brain waves related to perceptual and decision processes, and generated less activity in brain areas associated with effortful action control. In our discussion, we reflect on the status quo of physiological research on implementation intentions, methodological and conceptual issues, related research, and propose future directions.

People are motivated to process threatening information in a defensive manner. For instance, in self-reports, group members consistently reject threatening outgroup criticism compared with the same criticism from the ingroup (intergroup sensitivity effect). Because self-reports are a poor proxy for actual behavior, it remains unknown whether this defensiveness motivates hostile actions. We fill this gap in the literature: Five experiments (total N ϭ 787) show that group members pay to punish critical outgroup comments, exclude outgroup commenters from a subject pool, and reject ultimatum bargaining offers from outgroup commenters compared with ingroup commenters voicing the same criticism. These defensive behaviors represent hostile actions and are robust in a meta-analysis across our 5 studies. Intergroup sensitivity thus motivates hostile defensive actions. We discuss potential consequences for intergroup relations.

Group members defensively reject out-group criticism in self-reports because they perceive it as more threatening than the same criticism from the in-group (intergroup sensitivity effect). But does this effect motivate action? In five experiments, group members exhibited behavior patterns characteristic of motivated goal pursuit: They prioritized defending their group over completing their individual work (Experiments 1-5), even when work was intrinsically rewarding (Experiment 2) or incentivized (Experiment 3). Lastly, this effect disappeared when group members had attained their goal of protecting their group by other means (i.e., group affirmation; Experiments 4 and 5). Together, the experiments suggest that intergroup sensitivity motivates goal-directed action. We discuss how motivated collective defensiveness may undermine constructive debate and heighten acrimony between groups.