Motivated election, voice changes, and orienting: Dichotic processing of attended and unattended audio messages

Attention has been defined by James (1890) as the willful act of focusing on some things at the expense of others. Implied in his description is the act of selection – choosing to devote processing resources to some things in the environment while ignoring other things. Selection acts as the stepping down process between perception and memory; the capacity limitations in the brain allow only so much information to be retained. Filter theory (Broadbent, 1958) provides one plausible explanation for selection. An attentional filter acts a gatekeeper by allowing attended information to pass into memory all the while barring unattended information from accessing processing resources. Filter theory is an early selection account of attention in that unattended information is disregarded early in the processing hierarchy. Research supporting filter theory has shown that physical cues in the environment are reliable tools that allow people to attend to stimuli based upon their intention to do so. In other words, the filter may be set in order to facilitate discrimination between competing stimuli. Some findings, however, have shown that unattended stimuli may pass the attentional filter. The late selection account (Deutsch & Deutsch, 1963) holds that unattended stimuli, once perceived, may not be immediately discarded from memory. Instead, information may be processed and then rejected if it does not meet particular criteria (such as the physical cues described in filter theory). As opposed to early selection, in which explicit memory is typically used to assess attention, many late selection studies have used dependent measures more indicative of implicit memory. The current study was designed to add to the literature on selective attention. Instead of approaching the subject from an early or late selection perspective, this study used a theoretical framework based upon attenuation theory (Treisman, 1960; 1964a). The concept of attenuation suggests that the attentional filter described by Broadbent (1958) may not be rigid; items may not be selected on an all-or-none basis. Instead, there may exist certain conditions that will attenuate the filter, such that stimuli meeting those conditions will be processed whether they are attended or not. One such condition may be valence, as the affective quality of a stimulus could influence processing. In addition, two variables (structure and load) were included to account for recent findings in literature. Participants (n = 49) in the study performed a dichotic listening task while shadowing material in an attended channel. Heart rate and electrodermal activity were recorded as physiological measures indicative of cognitive responding. Signal detection was included to provide an assessment of explicit memory. The results of the study did not support any predictions – valence, structure, and load seemed to have no impact upon responding. A closer analysis of the physiological data revealed two interesting findings, however. First, a large, general increase in sustained heart rate over the course of the shadowing activity indicated that the task was extremely difficult and demanding. It was so difficult that it may have prevented any possible effect from any independent variable from being detected. This conclusion is supported by the fact that no main effect was found for the perceptual load condition. Second, a small interaction effect was discovered revealing that when voice changes (structure) and negative words (valence) appeared together, a cardiac orienting response occurred. This result hints that under the right conditions a shift in attentional resources may occur. Implications for the study include reevaluating shadowing and the dichotic listening paradigm given participants struggle with the procedures. Also, despite the difficulty of the tasks, some shifting of resources may have occurred. If so, it is evidence that despite strong circumstances to the contrary, selection may be a more complicated process than once originally thought.