Spatial vision and aging. II: Criterion effects.

The first paper in this series suggested that, in order to see gratings of low spatial frequency, observers in their 70s needed three times as much contrast as did observers in their 20s. Here, we use a signal detection procedure to determine if this age difference was due to actual changes in vision with age or was merely an artifact of changes in criteria for saying that a target was visible. The results show the following: older observers have a genuinely diminished ability to see gratings of low spatial frequency; older observers tend to lack confidence in their judgments of what they had seen; younger, but not older, observers grow more confident of their judgments as gratings become easier to see.