The results of a study of four groups of beagles, each experiencing a different combination of antioxidant supplementation and behavioural enrichment over a two-year period, are published in the January 2005 issue of Neurobiology of Aging.

In October 2003, a separate study conducted at the University of Toronto showed that old dogs that were on diet fortified with antioxidants such as vitamin E, vitamin C, and beta-carotene performed better on a variety of cognitive tests than dogs that were not on the diet.

"Although we found that not all cognitive functions respond to antioxidant treatment, our data suggests that antioxidants play an important role in preventing or slowing age-related cognitive impairments," said Dr Dwight Tapp.

In the latest study, one group of elderly dogs was fed a regular diet combined with regular experience. The second group received a regular diet and enriched experience; the third group an enriched diet and regular experience; and the fourth group both an enriched diet and an enriched experience.

Researchers noticed that the effect of combining the two treatments produced 'statistically-significant' benefits on a dog’s ability to learn, compared to administering either treatment on its own.

“We were really surprised just how clear-cut the benefit is of using a combined therapy,” said lead investigator and psychology professor Bill Milgram.

“Since humans and dogs have many biological and behavioral parallels, I predict similar results would be attained in people,” he added.

Like humans, dogs lose some of their ability to learn new information as they get older and suffer from both long-and short-term memory lapses.