Accelerated growth following a period of a poor diet can lead to slower learning performance in adulthood, University of Glasgow researchers have found.

Professor Pat Monaghan of Glasgow University, said: "When an animal experiences a period of poor quality food during growth, then when environmental conditions improve, it can accelerate growth to catch up in body size.

"What we have found is that this very rapid growth can carry long term costs ﾖ in our study the greater the growth spurt in the chick, the poorer the learning performance of the adult."

The study focused on the early growth of zebra finches.

The findings of this study, funded by the Natural Environment Research Council, appear to be common across other species.

Professor Monaghan said: "Studies of humans and early nutrition have also found that low birth weight babies, who then grow quickly when fed an enriched diet, have a similar lower performance when tested at nine months than babies given a normal diet. Unlike the finches though, this effect seems not to be so long lasting in humans.

"In the zebra finch study, we provided siblings with unlimited amounts of different quality food for a short period after hatching. Those that got the lower quality diet, which had less protein and vitamins, were then switched to the normal food.

"To test the long term effect on learning abilities, we then gave all the birds a simple learning task involving finding food behind coloured screens when they were adults.

"Although all the birds eventually learned the task, how fast they did so was related to rate of compensatory growth they had undergone as chicks; birds that had grown fastest when switched to the normal diet were slowest to learn the task.

"The results suggest that accelerating growth can have long lasting negative consequences for learning ability. What is not clear at this point is whether the learning defects stem from behavioural, hormonal or neural changes.

"It is possible that resources normally dedicated to these pathways are diverted to support the accelerated growth. But in the harsh, competitive world of nature, being big may simply be more important than being bright."

Kate Richardson (k.richardson@admin.gla.ac.uk)

For more information or to speak to Dr Monaghhan, please contact the University of Glasgow Media Relations Office on 0141 330 3535 or email k.richardson@admin.gla.ac.uk

1. After hatching, the birds were raised on either a normal or low quality diet for 20 days and then switched to the higher quality standard diet. To test the birds? learning performance, the researchers placed them in a circular foraging area with corridors leading to a screen with cups of seed behind it. They were then trained to associate a yellow screen with food.

2. Zebra finches are common cage birds in the UK, originating from Australia.

3. Pictures of zebra finches available from Glasgow University Press Office

4. NERC is one of the UK's eight Research Councils. It uses a budget of about ?350m a year to fund and carry out impartial scientific research in the sciences of the environment. NERC trains the next generation of independent environmental scientists. It is addressing some of the key questions facing mankind, such as global warming, renewable energy and sustainable economic development.

First published: 28 August 2006