Are verbal transformations sensitive to age differences and stimulus properties?

Verbal transformations are illusory changes that arise from listening to a spoken word repeated over and over for a prolonged period of time. Past research has yielded some evidence of age differences in participants' reports of verbal transformations. The goal of the present study was to examine reports of illusory percepts in young and older adults to determine whether participant characteristics (i.e., age, cognitive integrity, hearing acuity, vocabulary knowledge, and mood) and differences in sensitivity to properties of the stimulus material could account for age-related declines in reports of illusory changes. We observed age-related declines in new forms (illusory percepts) but merely a trend in the same direction for transitions (changes from the veridical sensory experience to illusory percepts and reversals to either the veridical sensory experience or other percepts). There was no evidence that participant characteristics other than age accounted for reports of illusory changes. However, we found age differences in participants' sensitivity to properties of the stimulus material: Young adults but not older adults were sensitive to the frequency of the veridical percepts. In contrast, both age groups were sensitive to the size of the neighborhood of similar-sounding words. These findings are discussed regarding the transmission deficit hypothesis (MacKay & Burke, 1990).