Mixed-list presentation and visual field asymmetry: attempts to differentially activate the hemispheres

Mixed lists of abstract nouns and random forms were presented in an attempt to induce differential activation of the two hemispheres. For Expt. 1, nine probability levels, from P = 0.1 to P = 0.9 for both nouns and forms were examined. Prior to the presentation of each trial a cue was presented which gave the probability of that trial being either a noun or a form. For Expts. 2 and 3, eleven mixed blocks were presented, each containing a different proportion of nouns and forms. The activational model predicts right visual field (RVF) advantages for both stimulus types when nouns are more probable or more frequent than forms, and left visual field (LVF) advantages for both stimulus types when forms are more probable than nouns. The structural model predicts RVF and LVF advantages for nouns and forms respectively, regardless of their probability of occurrence. It was found that the more probable or frequent the stimulus type the faster the response. However, all 3 experiments offered some support for the structural model and no support for the activational model.