Reliability and magnitude of visual laterality effects: further examination of the endogenous cueing procedure

The present study tests the hypothesis that laterality effects with bilateral displays would be larger and more reliable when lexically matched stimulus pairs are used rather than unmatched pairs. A total of 40 right-handed participants completed a lexical decision task using matched stimulus pairs in a bilateral display. These data were added to a previously collected set of data with 40 right-handed participants in which unmatched stimulus pairs were used. Results showed that the expected right visual field advantage (RVFA) was significant in words but not in non-words. In addition, a significant practice effect was found to be larger for matched than unmatched stimulus pairs. The predicted interaction between stimulus type, stimulus pairing, and visual field was not significant; contrary to the initial hypothesis, the RVFA was larger (though not significantly so) for unmatched displays than for matched ones. Finally, the laterality effect was found to be more reliable with unmatched than matched pairs in non-words, whereas no difference was found in words. The discussion emphasises the advantages of unmatched stimulus pairs and the conditions under which the bilateral effect is likely to emerge.