Six-Month-Old Babies Appear to Estimate Probabilities

In a new study, researchers discovered that babies as young as six months old are capable of estimating probabilities. The research was conducted by neuroscientists at the Max Planck Institute for Human Cognitive and Brain Sciences (MPI CBS) in Leipzig, Germany, and the University of Uppsala in Sweden.

“Six months seems to be the minimum age at which infants start to deal with probability information. One previous study showed that babies at just four months old were not able to perform this task and therefore seemed to not yet be sensitive to this information,” said study leader Dr. Ezgi Kayhan, neuroscientist at MPI CBS.

“We suppose that from early on in life, our brains represent statistics of the environment. Within the first six months of life, babies are able to extract information about which events follow on from each other, or how likely one event is compared to another.”

For the study, the researchers presented animated film clips to 75 babies aged six months, twelve months and 18 months. These short movies featured a machine filled with balls, most of which were blue, with a few yellow ones. In a second sequence, the machine ejected large amounts of the mainly available blue balls into one basket, and into another container mainly yellow balls.

In this context it was 625 times less likely that the machine chose yellow balls instead of blue. Therefore, the basket being filled with mainly yellow balls was a highly unlikely event.

While the babies watched the film clips, the scientists observed them using an eyetracking technique to see which of the two baskets they looked at longer — the likely or the unlikely option.

“We noticed that the infants stared longer at the unlikely option independently from the tested age group to which they belonged — presumably because they were surprised that it was just made up of the rare yellow balls and that it was therefore a very improbable event,” Kayhan said.

To make sure that the babies were not just more attracted by the color yellow in some of the trials, the researchers conducted a similar experiment with green and red balls.

Next, the research team wanted to test the limits of these estimations: Are babies still sensitive to this information when the likely and unlikely samples are difficult to distinguish?

Indeed, the babies’ focus changed depending on the ratio of blue and yellow balls. When it was only nine times more likely that the machine would pick the blue ball instead of a yellow one, the babies preferred to look at the likely blue-dominated sample for a longer period of time.

“This outcome was especially surprising. One explanation could be that with decreasing ratio between the two colours, the complexity of the information increased and therefore infants preferred to focus their attention on the subset that looked more familiar,” said Kayhan.

“From previous studies it is known that babies prefer to look at familiar objects if they still need to encode information. In the difficult case, the information was more complex, thus the processing load was heavier within this time period.”

Regardless of a potential explanation, the findings show that the infants’ ability to estimate probabilities strongly depends on how difficult it is to differentiate between the likely and the unlikely sample.

Source: Max Planck Institute for Human Cognitive and Brain Sciences