Bilateral stimulus presentation in memory scanning.

Abstract

Participants performed a memory-scanning task (Sternberg, 1966(Sternberg, , 1969a in which probe letters were displayed unilaterally or bilaterally after sets of two, four, or six letters were memorized. The mean response time (RT) to bilateral presentations was significantly longer than the mean RT to unilateral presentations, but the slope of the set-size function was not affected, suggesting that presenting stimuli bilaterally affected stages other than memory scanning. There were no significant visual-field effects in either the bilateral or unilateral conditions, suggesting that memory scanning is not a lateralized process. There was no evidence that bilateral presentation increased visual-field differences. This is not consistent with Boles' (1983, 1990) hypothesis that visual-field asymmetry effects are more pronounced with bilateral than with unilateral presentation of stimuli.Resume Les participants ont ete soumis a un test de balayage de la memoire (Sternberg, 1966(Sternberg, , 1969a dans lequel les lettres ciblees etaient placees unilateralement ou bilateralement apres memorisation d'ensembles de deux, quatre ou six lettres. Le temps de reponse moyen (TR) aux presentations bilaterales etait beaucoup plus long que le TR moyen aux presentations unilaterales, mais la pente de la fonction epaisseur n'etait pas affectee. Ceci suggere que la presentation bilaterale de stimuli a affecte d'autres stades que le balayage de la memoire. Nous n'avons constate aucun effet de champ visuel important, ni dans la condition bilaterale, ni dans la condition unilaterale, ce qui laisse supposer que le balayage de la memoire n'est pas un processus de laterisation. Nous n'avons pas pu prouver que la presentation bilaterale augmentait les differences dans le champ visuel. Ceci ne correspond pas a l'hypothese de Boles (1983Boles ( , 1990 selon laquelle les effets d'asymetrie du champ visuel sont plus prononces dans les presentations bilaterales de stimuli que dans les presentations unilaterales.