Carrasco, M., Evert, D.L., Chang, I. & Katz, S.M. (1995). The eccentricity effect: Target eccentricity affects performance on conjunction searches. Perception & Psychophysics, 57(8): 1241-1261.

The serial pattern found for conjunction visual search tasks has been attributed to covert attentional shifts, even though the possible contributions of target locations have not been considered. To investigate the effect of target location on orientation * color conjunction searches, the target's duration and its position in the display were manipulated. The display was present either until observers responded (Experiment 1), for 104 ms (Experiment 2) or for 62 ms (Experiment 3). Target eccentricity critically affected performance: A pronounced eccentricity effect was very similar for all three experiements; as eccentricity increased, reaction times and errors increased gradually. Furthermore, the set-size effect became more pronounced as eccentricity increased, and the extent of eccentricity effect increased for larger set sizes. In addition, according to stepwise regressions, target eccetricity as well as its interactions with set size were good predictors of performance. We suggest that these findings could be explained by spatial-resolution and lateral-inhibition factors. The serial self-terminating hypothesis for orientation * color conjunction searches was evaluated and rejected. We compared the eccentricity effect as well as the extent of orientation asymmetry in these three conjunction experiments with those found in feature experiements (Carrasco & Katz, 1992). The roles of eye movements, spatial resolution, and covert attention in the eccentricity effect, as well as their implications, are discussed.