Grow fast, learn slow

18 July 2006

Logo: University of Glasgow

Joint press release from the University of Glasgow and the Natural Environment Research Council

In a new study of zebra finches, scientists at Glasgow University have found that accelerated growth following an initial diet of poor quality food can result in slower learning in adulthood.

Professor Pat Monaghan of Glasgow University, said, "If environmental conditions improve for animals that have previously experienced a poor quality diet, their growth can accelerate to catch up in body size. We have found that this very rapid growth can carry long term costs - in our study on birds the greater the growth spurt in the chick, the poorer the learning performance of the adult."

The findings of this research, funded by the Natural Environment Research Council, appear to be common across other species. Studies of humans and early nutrition have also found that low birth weight babies who grow quickly when fed an enriched diet have a similarly lower performance when tested at nine months compared with babies given a normal diet. Unlike the finches 'though, this effect seems not to be so long lasting in humans.

In the zebra finches study, the scientists 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, the scientists gave all the birds a simple learning task involving finding food behind colour screens once they reached adulthood. Although all the birds eventually learned the task, how fast they did so was related to the 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 be more important than being bright.

Further information

Professor Pat Monaghan
Environmental and Evolutionary Biology
University of Glasgow
Tel: 0141 330 5968 (work)
Tel: 01360 550241 (out of hours)
Mob: 0787 6266541

Ray McHugh
Glasgow Press Office
Tel: 0141 330 3535

NERC Press Office
Natural Environment Research Council
Polaris House, North Star Avenue
Swindon, SN2 1EU
Tel: 01793 411561
Mob: 07917 557215

Notes

1. The research is published today in PLoS Biology.

2. 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.

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

4. Pictures of zebra finches are available from Glasgow University Press Office.

5. NERC is one of the UK's 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.

Grow fast, learn slow

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