Elucidating different aspects of speed of information processing: comparison of behavioral response latency and P300 latency in a modified Hick reaction time task

摘要

The aim of the present work was to get a more detailed understanding of the functional significance of the P300 latency. P300 latency is often used as measure of stimulus evaluation time. However, the interpretation of P300 latency as stimulus evaluation time was challenged by findings of a P300 latency sensitivity to response-related manipulations. In two studies with samples from two different countries, not only RT, but also P300 latency were used as measures of speed of information processing examining the Hick paradigm. P300 latency has been used as speed of information processing measure before, but to my knowledge never in the Hick task. The advantage of using the Hick paradigm is that the influence of response selection on P300 latency can be systematically investigated while keeping stimulus evaluation constant and minimal. Furthermore, a comparison of P300 latency and RT revealed some more information about the functionality of P300 latency. By contrasting both speed of information processing measures as predictors of intelligence, it was also investigated if RT and P300 latency explain common and/or unique parts of variance in intelligence. The present investigation replicated once more the increase of RT in dependence of the amount of bit of information that needs to be processed. Furthermore, in accordance with the mental speed approach of intelligence, participants with higher intelligence were performing faster in the Hick task than participants with lower intelligence levels. Moreover, this inverse relation between RT and intelligence was enhanced across complexity. In addition, the present work also revealed some new insights about the functional significance of P300 latency. These insights are the following:ud1. A clear P300 component was elicited under all four bit conditions, including the 0 bit condition. This indicates that even in simple reaction time tasks some cognitive processing is activated. P300 is often associated with a context updating of the current mental representation in the working memory. Since each stimulus under the 0 bit condition is exactly the same as the previous one, present data suggests that P300 mightudhave other or additional functions than context updating. One alternative function could be a monitoring role, which is determining the stimulus-response association.ud2. P300 latency did increase across bit conditions. This indicates that P300 latency is not only sensitive to manipulations that focus on stimulus evaluation, but also to manipulations focusing on response selection. This finding is not compatible with the idea of P300 latency as an index of stimulus evaluation time.ud3. RT and P300 latency are often expected to capture the time of similar underlying processes. Indeed, P300 latency is, similar as RT, increasing across bit conditions. However, P300 latency and RT were not related. This suggests that P300 latency and RT are not reflecting the same aspects of speed of information processing. P300 latency might be proportional to stimulus evaluation time in task that focus on stimulus evaluation. But, as the current results show, it is probably determined by completely different processes than RT. Further research is needed to get a more complex pictures of the determinants of the P300 component.ud4. The relation between P300 latency and intelligence is still not clear. Present data does not confirm the suggestion of Houlihan et al. (1998) that the relation of RT and intelligence might be partly mediated by response-related processes. However, there might be other factors like subjective task difficulty and complexity, or the subject’s strategy that play a significant role in individual differences in both, P300 latency and intelligence. Further research is needed to get a more complex pictures of these factors.