Monetary incentives in speeded perceptual decision: effects of penalizing errors versus slow responses.

The influence of monetary incentives on performance has been widely investigated among various disciplines. While the results reveal positive incentive effects only under specific conditions, the exact nature, and the contribution of mediating factors are largely unexplored. The present study examined influences of payoff schemes as one of these factors. In particular, we manipulated penalties for errors and slow responses in a speeded categorization task. The data show improved performance for monetary over symbolic incentives when (a) penalties are higher for slow responses than for errors, and (b) neither slow responses nor errors are punished. Conversely, payoff schemes with stronger punishment for errors than for slow responses resulted in worse performance under monetary incentives. The findings suggest that an emphasis of speed is favorable for positive influences of monetary incentives, whereas an emphasis of accuracy under time pressure has the opposite effect.

Monetary reward increases attentional effort in the flanker task.

An important question is whether monetary reward can increase attentional effort in order to improve performance. Up to now, evidence for a positive answer is weak. Therefore, in the present study, the flanker task was used to examine this question further. Participants had to respond sooner than a certain deadline in a flanker task. One group of participants received a performance-contingent monetary reward, whereas the other group earned a fixed amount of money. As a result, monetary reward significantly improved performance in comparison with the control group. The analysis of speed-accuracy trade-off functions revealed that monetary reward increased attentional effort, leading to an enhanced quality of stimulus coding. Little evidence was found that reward also improved selective spatial attention.

The effect of element spacing on hemispheric asymmetries for global/local processing.

In several studies with hierarchical stimuli it has been shown that the left and the right hemispheres are specialized for the processing of local and global information, respectively. However, although corresponding visual-field (VF) effects regularly show up for incongruent stimuli, they are often absent for congruent ones. In this study, it was investigated whether the spacing between the elements of the stimuli has any effect on this phenomenon. Therefore, in Experiment 1, stimuli with narrowly spaced elements were applied. As a result, VF-effects occurred independently of the congruency condition. For comparison, stimuli with wider element spacing were used in Experiment 2. Under these conditions, VF-effects occurred again, as expected, only for incongruent stimuli. These results show that element spacing can have an effect on VF-effects. The results are interpreted in the sense that narrowly spaced elements are perceived as texture, which always leads to an elaborate mental representation of the stimulus that differs between the hemispheres.