POSITION-DEPENDENT AND POSITION-INDEPENDENT ATTENTION SHIFTS - EVIDENCE AGAINST THE SPOTLIGHT AND PREMOTOR ASSUMPTION OF VISUAL FOCUSING

One implication of the spotlight metaphor of visual-attention shifts i s that attention moves from position to position, from one object in t he visual field to another. According to this view, attention shifts s tart at the last-focussed position, their spatiotemporal course theref ore being position dependent. A different, yet also position-dependent , formulation is implied in the so-called ''premotor hypothesis of att ention'' (Rizzolatti et al., 1987; Umilta et al., 1991). In this paper these two accounts are tested against an alternative, position-indepe ndent conception. It is maintained that in the case of onset-triggered processes, the course of the attentional shifts is independent of the last-focussed position. On the basis of these considerations, three e xperiments measure choice-reaction times of stimuli at different spati al positions after peripheral cuing of the same or another position wi thin the visual field. Results show no evidence for the position-depen dent conception of the spotlight metaphor or the premotor hypothesis w ith a long SOA (stimulus-onset asynchrony) between cue and stimulus. O nly with a short SOA is the premotor hypothesis supported by the data. As an alternative interpretation, a position-independent thesis is fa vored, in which it is assumed that attention shifts can be adjusted du ring an early stage of processing.