Involuntary attentional shifts as a function of set and processing fluency.

In laboratory tasks, involuntary cognitions of various kinds (e.g., mental imagery) have been elicited by external stimuli. These effects reveal, among other things, the capacities of involuntary processes. In most cases, these cognitions do not require, for their generation, executive functions such as a shift in selective attention. In Experiment 1, subjects were presented with a clock of 12 words in the stead of numbers and were instructed to focus on the center of the screen and to not count the number of letters of a word at a certain location. Involuntary counting of the critical word occurred on 39% of the trials. This effect requires an involuntary shift of attention. Experiment 2, involving Chinese ideographs, concerned the effect of stimulus fidelity and processing fluency. Native English speakers and a separate group of subjects who could read Chinese ideographs were presented with an array similar to that of Experiment 1 and instructed to not read any of the words. Some words were easy to read (e.g., regular Chinese words and English words), and some words were more difficult to read (e.g., Chinese "loan" words and English pseudowords). For the subjects who could read Chinese ideographs, more involuntary reading occurred for regular ideographs than for loan words. For the Native English speakers, comparable effects were found with the English stimuli. Together, these studies reveal that attentional phenomena of this kind can be influenced involuntarily and systematically through external control.