Strategic behavior without awareness? Effects of implicit learning in the Eriksen flanker paradigm.

This experiment investigated whether subjects' selection and use of strategies in detecting a target letter in a flanker task requires intention. Subjects' expectancies for compatible and incompatible trials (trials on which the response to the flanker stimulus was consistent or inconsistent with the target response) were manipulated by presenting cues that signaled the occurrence of these types of trials. Three groups of subjects received explicit, partially explicit, or implicit instructions about the meaning of the cues. By the end of the experiment, all the groups were able to select and use strategies based on the cues to improve their performance. However, this strategy selection developed slowly with practice in the latter two groups, whereas it was present from the outset in the first group. In addition, forced choice tests performed after the experiment showed that the subjects in the implicit condition could not intentionally indicate which stimuli were most likely to follow a given cue. Thus, the data suggest that the selection of strategies occurred outside the subjects' awareness, and without their intention.

Voluntary control of Necker cube reversals modulates the EEG delta- and gamma-band response.

Reversible figures such as the Necker cube make up a well-known class of visual phenomena in which an invariant stimulus pattern gives rise to at least two different perceptual interpretations. Former EEG studies of our research group demonstrated a reversal-related delta response and a frontal enhancement of gamma activity during multistable perception which has been interpreted as signaling attentional top-down processes. The aim of the present study was to investigate the functional involvement of delta and gamma activity in top-down processes more explicitly by asking 21 healthy participants to bring the reversal rate under voluntary control during viewing of the Necker cube. Slowing down the reversal rate should be accomplished by focussing attention to the currently perceived alternative while speeding up should be accomplished by shifting attention as rapidly as possible from one perspective to the other. EEG was recorded from frontal, central, parietal, and occipital locations of both hemispheres. The data was analysed on the single-sweep level in the delta and gamma frequency range. The results showed that both delta response and gamma power were larger during slowing down than speeding up the reversal rate. These findings may indicate that more attentional resources have to be allocated by the cognitive system in order to prevent a reversal by means of focussed attention than to initiate a reversal by attentional shifts.

Neuroendocrine response to casino gambling in problem gamblers.

Problematic gambling is thought to be influenced by neurobiological mechanisms. However, the neuroendocrine response to gambling is largely unknown. Therefore, the effect of casino gambling on the sympathoadrenal system, the HPA-axis, and pituitary hormones were analyzed. Fourteen male problem gamblers and 15 non-problem gamblers were examined in a balanced cross-over design. In the experimental session, participants played blackjack in a casino wagering their own money. During the control session, subjects played cards for accumulation of points. Heart rate and endocrine measures were recorded at baseline, at 30, 60 and 90 min during gambling/card playing, and after the game. Heart rate and norepinephrine levels increased with the onset of blackjack in both groups, with problem gamblers showing significantly higher levels across the entire gambling session. In addition, dopamine levels were significantly higher in problem gamblers during casino gambling compared to non-problem gamblers. Cortisol levels were transiently increased with the onset of blackjack in both groups. Casino gambling as a "real life" situation induces activation of the HPA-axis and the sympathoadrenergic system, with significantly more pronounced changes in problem gamblers. These findings may contribute to a better understanding of neuroendocrine disturbances in problem gambling.

Criminal Behavior Associated with Pathological Gambling.

The influence of addictive gambling behavior on criminal behavior was examined in this study. A sample of pathological gamblers from in- and outpatient treatment centers and self-help groups (n = 300) and a sample of high and low frequency gamblers from the general population and army (n = 274) completed a comprehensive questionnaire which assessed social attachment, personality, pathological gambling and criminal behavior variables. The causal analysis of a Lisrel Model leads to the following results: addictive gambling behavior is an important criminogenic factor. This predisposing factor alone cannot sufficiently explain criminal behavior associated with pathological gambling. Personality variables also directly influence the intensity of criminal behavior. Social attachment variables have only an indirect effect. As far as property offenses are concerned, it was found that the direct causal effect of addiction behavior is greater than that of personality.