Directing Attention Toward Stimuli Affects the P300 But Not the Orienting Response

Whether attending to stimuli affects the orienting response and its habituation is not yet clear. EEG alpha suppression responses, electrodermal responses, and EEG evoked potential responses of two groups of subjects were compared. The Attend group was given instructions to pay attention to and count the 59 moderate intensity clicks (interstimulus interval = 15 sec). The Ignore group was instructed to “try not to let the clicks disturb your relaxed state.” Separate ANOVAs with repeated measures were used to evaluate all measures, and all showed significant effects for click repetition (habituation). Alpha suppression and change in log conductance showed no differences related to group. The P300 component of the average evoked potentials was significantly larger for the Attend group. We concluded that attending to, versus ignoring, stimuli does not have an appreciable effect on these two traditional measures of the orienting response, but it does affect the evoked potentials. The relationship between attention and “significance” is discussed.