Reliability and magnitude of visual laterality effects: the influence of attention

Two studies investigated the test-retest reliability of laterality effects in visual tasks. In each of the studies, 160 right-handed participants were tested. In Experiment 1, a lexical decision task was used under four testing conditions: no control of attention, fixation control, bilateral presentation with endogenous cue, and bilateral presentation with exogenous cue. In Experiment 2, the same four conditions were used in a letter-matching task in which participants had to indicate whether two letters in a different case had the same name. Results showed a significant right visual field advantage in the first testing session. However, this advantage was eliminated in the second session, suggesting that attention was not fully controlled by any of the procedures. In addition, the reliability of laterality effects was greater when control of attention was applied. The discussion focuses on the importance of controlling attention when assessing laterality by means of a visual task. Alternative explanations of the present findings are also considered.