EVIDENCE OF STRATEGIC EFFECTS IN THE MODULATION OF ORIENTING OF ATTENTION

Two models of visual orienting of attention are frequently described. Voluntary orienting is usually induced by central cues that direct sub jects' attention to a given location in the visual space. Automatic or ienting is provoked by presentation of peripheral cues. It is shown th at automatic orienting induces greater attentional costs and benefits, and is less under a subject's control (Jonides 1981). Furthermore, it is not similarly affected by factors such as signal eccentricity (Umi lta et al. 1991). The present experiment was undertaken to investigate how sensitive automatic orienting produced by peripheral cues is to v oluntary modulations of attention. In experiment 1, subjects facing si tuations daily in which attentional requirements are high, were compar ed to non-practiced ones. In experiment 2, other groups of practiced s ubjects facing high or low attentional-demanding situations were teste d. In both experiments, subjects were asked to respond to signals, pre sented in rapid succession, in one of two possible locations in space, on each side of central fixation point. The cue signal automatically oriented attention to one of the two locations in which a first stimul us was presented with 100% probability; 100 ms after the first respons e (RT1), a second response signal (RT2) was delivered either in the sa me location (valid condition) or in the opposite location (invalid con dition). Four cue probabilities were manipulated for this second stimu lus: 100%/0%, 80%/20%, 50%/50%, and 20%/80%. Two eccentricities of 3 d egrees and 6 degrees were tested. RT2 data demonstrated that (1) there was no eccentricity effect; (2) the higher the cue probability, the g reater were the attentional costs; (3) the attentional effects were sm aller in the practiced subjects who faced attention-demanding situatio ns daily, than in the other groups. Put together, these data suggest t hat automatic orienting of attention can be modulated by voluntary att entional processes, according to cue probability. Furthermore, experie nced subjects seem to be able to better distribute their attentional r esources in space, with increased task requirements. The adoption of a n optimal criterion might lead to the use of a cost minimizing strateg y.