The effects of age and intelligence on the dark-interval threshold

The threshold for the detection of the dark interval between two flashes of light (DIT) was investigated for 240 school children aged 6–17. It was found that the threshold showed a linear decline with chronological age. a finding attributed to physiological aging of the visual receptor system producing diminished persistence of the initial stimulus. This finding was counter to the expectation that the DIT would also indicate the growing potency of a higher-order cognitive process (temporal integration of stimulus traces) which would have caused the DIT to rise at some point along the chronological scale.