Tuning into abstract concepts like numerical rules is an ability we humans have generally restricted to ourselves and our closest primate relatives, but it is becoming clear we have underestimated other species' abilities.

"We show that pigeons can learn abstract numerical rules and apply them to numbers they have never seen before," said lead researcher Damian Scarf of the University of Otago in Dunedin, New Zealand, of the study published today in Science.

Peck the touch screen

Scarf and his colleagues now report that pigeons can order numbers 1, 2 and 3. To do this, the pigeons were tested with three images containing one, two or three objects and pecked their answers using a touch screen. The correct response, putting the images in ascending order (ie 1 > 2 > 3), rewarded the avian students with a wheat treat.

After prolonged training, the scientists examined the birds to see if this was simply rote learning, or if they had really grasped the concept. They presented the pigeons with images containing 1, 2, 3, 4, 5, 6, 7, 8 or 9 objects. The birds proved up to the task.

"If the pigeons have learnt an abstract rule then they should be able to respond to these novel pairs of numbers correctly," said Scarf; remarkably, they did. The response of the birds was indistinguishable from that of two rhesus monkeys that had been previously trained on this task....

Understanding when these structures of the brain change will help reshape our understanding of preclinical Alzheimer's disease, and the physiological changes that occur long before clinical symptoms appear. It's hoped that this will enable researchers to identify people who, though they currently appear healthy, are likely to develop Alzheimer's disease in the future.

"This may be a valuable method for early detection. It's most likely going to be useful in research at this point," said co-author Bradford Dickerson, a neurologist at Harvard University in the U.S. of the study published in the current issue of Neurology.

Years ahead of Alzheimer's symptoms

Physiological changes linked to Alzheimer's disease begin to occur years, even decades, before symptoms begin to show. This preclinical period can be identified by amyloid-β deposits, which are insoluble proteins that accumulate and interfere with neuron functioning in the brain......