A central-peripheral asymmetry in masked priming.

Masked primes presented prior to a target result in behavioral benefits on incompatible trials (in which the prime and the target are mapped onto opposite responses) when they appear at fixation, but in behavioral benefits on compatible trials (in which the prime and the target are mapped onto the same response) when appearing peripherally. In Experiment 1, the time course of this central-peripheral asymmetry (CPA) was investigated. For central primes, compatible-trial benefits at short stimulus onset asynchronies (SOAs) turned into incompatible-trial benefits at longer SOAs. For peripheral primes, compatible-trial benefits at short SOAs increased in size with longer SOAs. Experiment 2 showed that these effects also occur when primes and targets are physically dissimilar, ruling out an interpretation in terms of the perceptual properties of the stimulus material. In Experiments 3 and 4, the question was investigated as to whether the CPA is related to visual-spatial attention and/or retinal eccentricity per se. The results indicate that the CPA is independent of attentional factors but strongly related to the physiological inhomogeneity of the retina. It is argued that central and peripheral primes trigger an initial motor activation, which is inhibited only if primes are presented at retinal locations of sufficiently high perceptual sensitivity. The results are discussed in terms of an activation threshold model.