Temporal delay,type of forewarning,and resistance to influence

Previous researchers have manipulated forewarning by providing premessage information about the topic and position of the upcoming communication, or the communicator's persuasive intent. Subjects in the present experiment were force-warned either 10 min prior to the communication, or just before the message began of the speaker's topic and position, persuasive intent, or topic only. As hypothesized, forewarning of the communicator's persuasive intent inhibited persuasion regardless of the length of the delay period, but forewarning of the topic and position required a delay in order to confer resistance to subsequent persuasion, suggesting that although both manipulations have been called “forewarning they may lead to reduced persuasion through different mechanisms. Foreknowledge of the source's topic, but not his position also increased resistance to persuasion when followed by a delay period. The results were discussed in terms of both cognitive and motivational mechanisms that may underly the persuasion inhibiting effects of forewarning.     

Effects of a concurrent memory task on hemispheric asymmetries in categorization

Recent research on the division of processing between the two cerebral hemispheres has often employed two concurrent tasks to investigate the dynamic nature of hemispheric asymmetries. The experiment reported here explored the effects of two concurrent high-level cognitive tasks (memory retention and semantic categorization) on the direction and magnitude of hemispheric differences in the processing of words and pictures. Subjects were required to categorize words and pictures presented to either the left visual field-right hemisphere (LVF-RH) or the right visual field-left hemisphere (RVF-LH). The categorization could be performed while holding either verbal material in memory (digit span), pictorial material in memory (serial nonsense figure recognition), or with no concurrent memory task. The effects produced hemisphere-specific, material-nonspecific interference. The verbal task removed a RVF-LH advantage at word categorization and enhanced a LVF-RH advantage on picture categorization; the pictorial task interfered with picture categorization in the LVF-RH, while enhancing a RVF-LH advantage at word categorization. The results are discussed in terms of multiple resource models of hemisphere function, capacity limitations, and the functional locus of processing required to produce various dynamic hemispheric effects.