Susceptibility to illusions and cognitive style: implications for pharmacy dispensing.

Response distributions for five cognitive illusions and one visual illusion were examined in two samples, college students (n = 134) and pharmacists (n = 51). These illusions were selected for study on the basis of pharmacists' judgments about associations of illusions to common dispensing errors. Participants were categorized as Illusion-prone or Illusion-resistant, and distributions of such tendencies for the six stimuli used varied within samples. Significant differences between the two samples on illusion-proneness and resistance were observed for the "Moses' Ark" and -Fcount" illusions. Associations of Illusion-prone and Illusion-resistant responses to field-dependence, psychological type, and the cognitive orientations derived from Psychological Type Theory were examined. Field-independence-field-dependence was the only cognitive dimension associated with Illusion-prone and Illusion-resistant responding. Implications of the data for developing measures based upon visual and cognitive illusions to identify people with error-prone tendencies were discussed.