Coactivation, pop-out, and symmetry affect line discrimination

17 college students discriminated between vertical and horizontal target li nes flanked by vertical and horizontal distracters. Large displays with 3.0 -cm lines and small displays half this size were used. The distracters were positioned above and below the target or to the left and right of it, form ing Vertical and horizontal global orientations. The number of flankers sha ring the target's orientation was varied. Vertical targets and small displa y sizes were processed more quickly. Speed of responding did not differ for the two global orientations. There was no advantage for target lines consi stent with global orientation. The results were replicated in Exp. 2 with d iagonal flankers. This supports an explanation using stimulus compatibility , since diagonal lines do nor correspond to either of the response options and cannot induce a tendency to respond more to one target than another. Di splays with multiple symmetry were responded to faster than those with a si ngle symmetry which were faster than asymmetrical displays, supporting the idea that symmetrical axes parallel and perpendicular to the target orienta tion provide a facilitative frame of reference. Coactivation from same-orie nted flankers, pop-out from differences in orientation, and symmetry all in fluenced responding in these patterns.