all of the recent studies of psychological functions and electrophysiology of the brain measure evoked potentials ( Hillyard & Kutas, 1983), which may be a more sensitive neurophysiological correlate of behavior. A related point is that, while regression analysis depends on the reliability of the variables in the regression, we have no measure of the reliability of EEG parameters for the same stimulation conditions. Indeed, it would be difficult to obtain "testretest" reliability because one would expect EEGs to change when an event is repeated ( John & Schwartz, 1978). Third, the seventeen events coded in the commercials used in this study may not adequately sample the events which influence EEG. A different set of events might be able to explain more of the variance in EEG parameters. Also, although most of the events could be reliably coded in the commercials, complex events such as emotional and cognitive reactions were less reliably coded.
The results of this analysis can be useful in deciding which brain sites and frequency bands are most likely to yield information about reactions to advertising. For example, the parietal alpha EEG parameters seem to be a likely place to seek reactions to brand and message content of a commercial. The frontal beta 2 parameters might be a likely place to seek reactions to executional variables. The results also suggest that content is not necessarily responded to differently by the two hemispheres (although processes used to respond to content may well differ in the hemispheres).
The results of this analysis are an encouraging first look at the relationship between ongoing events and EEG-recorded brain reactions. The topic certainly warrants future research.
I thank Jerry Olson, Bill Ray and Susan F. Taylor for providing the EEG data in a form which was manageable to analyze, and Burt Leiman for help in the process of coding events in the content of the commercials.
Donchin, E., Kutas, M., & McCarthy, G. ( 1977). Electrocortical indices of hemispheric utilization. In S. Harnad, R. W. Doty, L. Goldstein, J. Jaynes, and G. Krauthamer (Eds.), Lateralization in the nervous system. New York: Academic Press.
Hillyard, S. A., & Kutas, M. ( 1983). Electrophysiology of cognitive processing. Annual Review of Psychology, 34, 33-61.