Previous research has shown a wide array of age-related declines in vision. Perceptual learning (PL) may be useful as a possible intervention to combat these declines. PL has been demonstrated to be specific to particular stimulus attributes used during the training, such as orientation and location within the visual field. A number of studies examining PL in older as well as younger individuals have also included external noise in their stimuli. However, no studies to date have examined how training difficulty and the presence of external noise during training affect PL and specificity in older individuals. The current study examined orientation specificity of PL in an orientation discrimination task in older individuals (mean age 71.73, range 65-91). Twenty-two older subjects participated in the study which consisted of seven 2-hour sessions each conducted on separate days. A two-interval forced choice procedure was used with two sequentially presented Gabor patches during which participants indicated whether the second Gabor was rotated clockwise or counterclockwise compared to the first. Thresholds were determined using QUEST for their trained and untrained standards tested on separate days, the testing order and trained standard were counter-balanced across subjects. During days 2 through 6 participants were assigned one of the standard orientations for training in either an easy or difficult training condition which either included external noise (the mid-noise level during testing) or a condition in which no external noise present. Days 1 and 7 used the same procedure to assess orientation discrimination thresholds at five levels of external noise. Results indicate significant learning and that specificity was related to the difficulty of training. In addition, training with external noise increased the degree of transfer to the untrained orientation. No significant differences between subjects prior to training were found.
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