The role of stimulus-driven versus goal-directed processes in fight and flight tendencies measured with motor evoked potentials induced by Transcranial Magnetic Stimulation.

This study examines two contrasting explanations for early tendencies to fight and flee. According to a stimulus-driven explanation, goal-incompatible stimuli that are easy/difficult to control lead to the tendency to fight/flee. According to a goal-directed explanation, on the other hand, the tendency to fight/flee occurs when the expected utility of fighting/fleeing is the highest. Participants did a computer task in which they were confronted with goal-incompatible stimuli that were (a) easy to control and fighting had the highest expected utility, (b) easy to control and fleeing had the highest expected utility, and (c) difficult to control and fleeing and fighting had zero expected utility. After participants were trained to use one hand to fight and another hand to flee, they either had to choose a response or merely observe the stimuli. During the observation trials, single-pulse Transcranial Magnetic Stimulation (TMS) was applied to the primary motor cortex 450 ms post-stimulus onset and motor-evoked potentials (MEPs) were measured from the hand muscles. Results showed that participants chose to fight/flee when the expected utility of fighting/fleeing was the highest, and that they responded late when the expected utility of both responses was low. They also showed larger MEPs for the right/left hand when the expected utility of fighting/fleeing was the highest. This result can be interpreted as support for the goal-directed account, but only if it is assumed that we were unable to override the presumed natural mapping between hand (right/left) and response (fight/flight).

To IMPRES or to EXPRES? Exploiting comparative judgments to measure and visualize implicit and explicit preferences.

We introduce an adaptation of the affect misattribution procedure (AMP), called the implicit preference scale (IMPRES). Participants who complete the IMPRES indicate their preference for one of two, simultaneously presented Chinese ideographs. Each ideograph is preceded by a briefly presented prime stimulus that is irrelevant to the task. Participants are hypothesized to prefer the ideograph that is preceded by the prime they prefer. In the present research, the IMPRES was designed to capture racial attitudes (preferences for white versus black faces) and age-related attitudes (preferences for young versus old faces). Results suggest that (a) the reliability of the IMPRES is similar (or even better) than the reliability of the AMP and (b) that the IMPRES and the AMP correlate significantly. However, neither the AMP nor the IMPRES were found to predict attitude-related outcome behavior (i.e., the preparedness to donate money to a charity benefiting ethnic minorities vs. the elderly). Further research is thus necessary to establish the validity of the IMPRES. Finally, we demonstrated that, unlike the AMP, the IMPRES allows for an in-depth assessment of unanticipated response patterns and/or extreme observations using multidimensional scaling algorithms.

Extinction of likes and dislikes: effects of feature-specific attention allocation.

The evaluative conditioning (EC) effect refers to the change in the liking of a neutral stimulus (conditioned stimulus, CS) due to its pairing with another stimulus (unconditioned stimulus, US). We examined whether the extinction rate of the EC effect is moderated by feature-specific attention allocation. In two experiments, CSs were abstract Gabor patches varying along two orthogonal, perceptual dimensions (i.e. spatial frequency and orientation). During the acquisition phase, one of these dimensions was predictive of the valence of the USs. During the extinction phase, CSs were presented alone and participants were asked to categorise the CSs either according to their valence, the perceptual dimension that was task-relevant during the acquisition phase, or a perceptual dimension that was task-irrelevant during the acquisition phase. As predicted, explicit valence measures revealed a linear increase in the extinction rate of the EC effect as participants were encouraged to assign attention to non-evaluative stimulus information during the extinction phase. In Experiment 1, Affect Misattribution Paradigm (AMP) data mimicked this pattern of results, although the effect just missed conventional levels of significance. In Experiment 2, the AMP data revealed an increase of the EC effect if attention was focused on evaluative stimulus information. Potential mechanisms to explain these findings are discussed.

Automatic motor activation by mere instruction.

Previous behavioral studies have shown that instructions about stimulus-response (S-R) mappings can influence task performance even when these instructions are irrelevant for the current task. In the present study, we tested whether automatic effects of S-R instructions occur because the instructed stimuli automatically activate their corresponding responses. We registered the lateralized readiness potentials (LRPs) that were evoked by the instructed stimuli while participants were performing a task for which those mappings were irrelevant. Instructed S-R mappings clearly affected task performance in electrophysiological and behavioral measures. The LRP was found to deflect in the direction of the response tendency that corresponded with the instructed S-R mapping. Early activation of the instructed response was observed but occurred predominantly on slow trials. In contrast, response conflict evoked by instructed S-R mappings did not modulate the N2 amplitude. The results strongly suggest that, like experienced S-R mappings, instructed S-R mappings can lead to automatic response activation, but possibly via a different route.

Feature-specific attention allocation overrules the orienting response to emotional stimuli.

Emotional stimuli are generally thought to be processed in an unconditional fashion. Recent behavioral studies suggest, however, that emotional stimulus processing is critically dependent on attention toward emotional stimulus features. We set out to test this hypothesis using EEG measurements and a modified oddball paradigm. Unexpected emotional stimuli evoked amplitude variations of the P3a (an ERP marker of attention orienting) when attention was directed to emotional stimulus properties but not when non-emotional stimulus properties were attended to. We conclude that emotional stimulus processing is not unconditional, but dependent on top-down attentional control.

On the malleability of automatic attentional biases: effects of feature-specific attention allocation.

In two experiments, we examined the extent to which automatic attentional biases, as indexed by performance in the emotional Stroop task (Experiment 1) and the dot-probe task (Experiment 2), are modulated by feature-specific attention allocation. In both experiments, participants were encouraged to attend to either affective stimulus information (affective groups) or non-affective semantic stimulus information (non-affective groups). In both experiments, an attentional bias towards negative stimuli was found in the affective groups but not in the non-affective groups. In Experiment 1, we also observed an attentional bias towards non-affective semantic stimulus information in the non-affective group but not in the affective groups. We argue that these effects are due to a modulation of automatic stimulus processing by feature-specific attention allocation. Our data demonstrate that automatic attentional biases toward negative stimuli are not unconditional but instead depend on the relevance of negative information. Moreover, the results of Experiment 1 suggest that attention is automatically biased towards non-affective stimulus dimensions that are currently relevant.

Unconscious semantic activation depends on feature-specific attention allocation.

We examined whether semantic activation by subliminally presented stimuli is dependent upon the extent to which participants assign attention to specific semantic stimulus features and stimulus dimensions. Participants pronounced visible target words that were preceded by briefly presented, masked prime words. Both affective and non-affective semantic congruence of the prime-target pairs were manipulated under conditions that either promoted selective attention for affective stimulus information or selective attention for non-affective semantic stimulus information. In line with our predictions, results showed that affective congruence had a clear impact on word pronunciation latencies only if participants were encouraged to assign attention to the affective stimulus dimension. In contrast, non-affective semantic relatedness of the prime-target pairs produced no priming at all. Our findings are consistent with the hypothesis that unconscious activation of (affective) semantic information is modulated by feature-specific attention allocation.

On the (un)conditionality of automatic attitude activation: the valence proportion effect.

Affective priming studies have shown that participants are faster to pronounce affectively polarized target words that are preceded by affectively congruent prime words than affectively polarized target words that are preceded by affectively incongruent prime words. We examined whether affective priming of naming responses depends on the valence proportion (i.e., the proportion of stimuli that are affectively polarized). In one group of participants, experimental trials were embedded in a context of filler trials that consisted of affectively polarized stimulus materials (i.e., high valence proportion condition). In a second group, the same set of experimental trials was embedded in a context of filler trials consisting of neutral stimuli (i.e., low valence proportion condition). Results showed that affective priming of naming responses was significantly stronger in the high valence proportion condition than in the low valence proportion condition. We conclude that (a) subtle aspects of the procedure can influence affective priming of naming responses, (b) finding affective priming of naming responses does not allow for the conclusion that affective stimulus processing is unconditional, and (c) affective stimulus processing depends on selective attention for affective stimulus information.