Line Bisection Across the Lifespan

Linda Rueckert

Northeastern Illinois University

To be presented at the annual meeting of the Psychonomic Society, Minneapolis, MN, November, 2004.

Patients with neglect due to right hemisphere (RH) lesions tend to underestimate the left side of long lines and overestimate the right side of short lines. Normal young adults show a mirror reversal of this pattern. Normal elderly adults show a pattern similar to neglect patients for long lines. If this reflects diminished RH capacity, elderly adults would be expected to exhibit a crossover similar to neglect patients for short lines. Seventy-seven subjects between the ages of 18 and 71 were shown 1, 2, 8, 16, and 28 cm bisected lines and asked whether they were bisected too far to the left or right. There was a positive correlation between “left” choices and age, indicating that older subjects perceived the right side of the line as longer, at all lengths. This suggests that the change in performance with age is due to a general shift in perceptual bias, and is not merely a mild form of unilateral neglect.