Animal World

Bad news for those who had bad grade in statistics. The Nature journal just revealed: rhesus monkeys are pretty good statisticians! They can accurately assess which of two behaviours is more likely to bring them a reward by summing together a series of probabilistic clues. And their reasoning is reflected in the firing rate of individual neurons in their brain. Hahahah, beaten by monkeys, you bad guys :).

The research was carried out by Tianming Yang and Michael Shadlen at the Howard Hughes Medical Institute and the University of Washington in Seattle. They tested the reasoning of two rhesus macaques by showing them a series of abstract shapes on a video screen. Each shape corresponded to a different probability that a drink reward would be associated with a red instead of a green target. In each trial, the monkey saw a sequence of 4 of 10 possible shapes then, had to choose which target to look at. The probability that the red target would give the reward was the sum of the probabilities for each of the four shapes; otherwise, the green target yielded the drink.

After several weeks of training on thousands of trials per day (OK, so the monkeys are not as bright as you), both macaques learned to match their choices closely to the actual probabilities revealed by the shapes they saw, choosing the correct target more than 75% of the time. This is the first time monkeys have been shown to make such subtle probabilistic inferences. “When we had monkeys doing it, I was pretty shocked,” says Shadlen.

Electrodes in the brain are also utilised to record the activity of 64 neurons in the lateral intraparietal area - a region on the side of the brain that is involved in attention and visual processing. It seems that the neurons responded to the first shape by firing at a rate proportional to the probability suggested by that shape. As each successive shape was shown, the firing rate changed to match the probability determined by all the shapes seen so far.

“We’re seeing neurons that are making computations,” says Shadlen. In particular, the neurons appeared to be computing the log likelihood ratio of red versus green rewards - exactly the sort of computation a statistician might do. “We’re exposing the basic elements, the fundamental biology of higher cognition,” says Shadlen. Further work should allow the researchers to begin to understand the decision-making process in more detail.

For Princes of Whales, the choice of life is: to sing and attract more mates, or to be quiet and get fat :).

Reseachers at the University of Sydney have tracked a population of humpback whales during the annual migration from low-latitude breeding areas to Antarctic feeding grounds. Using hydrophones to capture their song along with land-based observations, they calculated the swimming speed and singing status of each whale. While non-singing whales averaged 4 kilometres per hour, singers - which are always male - moseyed along at only 2.5 km/h.

A few singers were clocked at around 15 km/h, showing that it’s not impossible to sing and swim fast. So why slow down? It could be a strategy to squeeze a bit more breeding into the season. Slowing down lets the singer be heard by a procession of passing females. “It effectively gives them a larger audience,” says Noad, one of the researchers. Males that sing swim more slowly than those that don’t, possibly ending up with less time in the feeding grounds to fatten up for the next winter. On the other hand, singers may attract more mates.

New Scientist published a research at the University of Alcalá in Spain. To measure the health of a bird population without having to catch birds and run tests on them, the researchers said, just count the spots on their eggs. The spottier the egg, the more stressed the parent, the team has found.

The team photographed 112 blue tit (Cyanistes caeruleus) egg clutches in central Spain, weighed the parents and ran blood tests. They found that females that laid eggs with more spots weighed less and had higher cellular concentrations of a stress-related protein called HSP70 than females that laid less spotty eggs.

The team suggests that the eggshell pigment protoporphyrin is responsible for the correlation. Levels of the pigment chemical rise as stress levels increase in the female, which would explain the greater coloration in the eggshell when it is laid. Egg speckling could be a cue for male blue tits to work harder to feed underweight chicks. Alternatively, speckling may be a cue to abandon the nest and find a healthier female.

“This could be really useful, since almost all of the endangered Hawaiian birds we work with have spotted eggs,” says Alan Lieberman at San Diego Zoo in California.