Two "same-different" reaction time experiments, analogous in task demands made on the S, were designed to test laterality differences in. perception. Ten normal right-handed Ss performed a verbal task in which they decided whether or not two three-letter words belonged to the same conceptual class. Ten different Ss performed a spatial task in which they decided whether two 16-cell matrices with 3 blackened cells were identical. Reaction times were found to be sensitive to laterality differences in perception. Verbal stimuli were processed faster when presented in the right visual field, and thus projected directly to the left cerebral hemisphere; spatial stimuli were processed faster when presented in the left visual field, and thus projected directly to the right cerebral hemisphere. These results were analyzed in terms of implications regarding hemispheric asymmetries for processing of verbal and spatial material and the nature of interhemispheric transfer of information.

The term warning is applied to a variety of stimuli. From a safety standpoint, the most appropriate definition of warning ties it to any information that has the potential to change behavior and prevent accidents. The results of an extensive literature review suggest that warnings are unlikely to be effective unless a series of conditions are met. The failure of many intended warnings, including most on-product warning labels, to reduce accidents reflects the difficulty of overcoming the problems inherent in their use.

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