External distraction impairs categorization performance in older adults.

The detrimental influence of distraction on memory and attention is well established, yet it is not as clear whether irrelevant information impacts categorization abilities and whether this impact changes in aging. We examined categorization with morphed prototype stimuli in both younger and older adults, using an adaptive staircase approach to assess participants' performance in conditions with and without visual distractors. Results showed that distraction did not affect younger adults, but produced a negative impact on older adults' categorization such that there was an interaction of age and distraction. These results suggest a relationship between the increased susceptibility to visual distraction in normal aging and impairment in categorization.