Study Ties Speed of Visual Discrimination to Cognitive Ageing

A team of researchers have presented a strong association between decline in visual perception speed and age-related fall in intelligence.

The finding, documented in the journal Current Biology, is based on experiments conducted on 600 healthy older people. During the experiments, the participants were shown brief flashes of one of two shapes on screen, during which the researchers measured the time each of them took to reliably differentiate one from the other.

The same tests were repeated at ages 70, 73 and 76. This is one of the first studies that evaluated the hypothesis that changes they observed in measures called 'Inspection Time' might be linked to the changes in intelligence in old age.

"The results suggest that the brain's ability to make correct decisions based on brief visual impressions limits the efficiency of more complex mental functions," said Stuart Ritchie of the University of Edinburgh. "As this basic ability declines with age, so too does intelligence. The typical person who has better-preserved complex thinking skills in older age tends to be someone who can accumulate information quickly from a fleeting glance."

Studies conducted earlier revealed smarter people did better in identifying the difference between the two briefly presented shapes. But, till date no study has looked at how the measures might alter over time as people age.

"What surprised us was the strength of the relation between the declines," Ritchie said. "Because inspection time and the intelligence tests are so very different from one another, we wouldn't have expected their declines to be so strongly connected."

The study indicated the gradual loss in simple visual decision-making processes might trigger decline in complex decision-making, what is otherwise called as general intelligence.

"Since the declines are so strongly related, it might be easier under some circumstances to use inspection time to chart a participant's cognitive decline than it would be to sit them down and give them a full, complicated battery of IQ tests," he said.