# Probability calculations—even babies can master it

##### November 3, 2017, Max Planck Society

One important feature of the brain is its ability to make generalisations based on sparse data. By learning regularities in our environment it can manage to guide our actions. As adults, we have therefore a vague understanding of which events are likely to happen. So far, it was unclear when we begin to estimate likelihood. Scientists at Max Planck Institute for Human Cognitive and Brain Sciences have now shown that even six-month-old babies can probability.

Our whole life we have to make decisions and weigh up probabilities of different events. By learning to estimate which event is more likely to happen, we become better at analysing risks and benefits to guide our actions. But when do we start to gain a sense of stochasticity? Are even able to determine likelihood?

Scientists at the Max Planck Institute for Human Cognitive and Brain Sciences (MPI CBS) in Leipzig and the University of Uppsala, Sweden, have now discovered that even six-month-old babies can estimate probabilities. The babies already succeed in determining which colour makes up the majority of the balls and therefore which one is more likely to be drawn. "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", says Ezgi Kayhan, neuroscientist at MPI CBS and leader of the underlying study. "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."

The neuroscientists investigated these relations by presenting animated film clips to 75 babies aged six, twelve and 18 months. These short movies featured a machine filled with balls, most were blue, some yellow, which in a second sequence ejected lots 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 very unlikely event.

While the babies watched the movies the scientists observed them using the so-called eyetracking method to see which of the two baskets they looked at for 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", explains the Turkish-born scientist. To make sure that the babies were not just more attracted by the colour yellow in some of the trials, the researchers also used green and red balls.

"In fact, several studies have already investigated whether infants can assess probabilities, but we've been the first to research whether the difficulty level of the likelihood information makes a difference", Kayhan states. Accordingly, Kayhan and her team wanted to test the limits of these estimations: Are babies still sensitive to this information when the likely and unlikely sample are difficult to distinguish?

Indeed, the babies' looking preferences 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 instead of a yellow one, the babies preferred to look at the likely blue-dominated sample for longer. "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. 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 was more complex, thus the processing load was heavier within this time period", Kayhan adds. Regardless of a possible explanation the study made clear that the infants' ability to estimate probabilities strongly depends on how difficult it is to differentiate between the likely and the unlikely sample.

Explore further: Infants know what we like best, study finds

More information: Ezgi Kayhan et al, Infants Distinguish Between Two Events Based on Their Relative Likelihood, Child Development (2017). DOI: 10.1111/cdev.12970

## Related Stories

#### Infants know what we like best, study finds

July 27, 2017
Behind the chubby cheeks and bright eyes of babies as young as 8 months lies the smoothly whirring mind of a social statistician, logging our every move and making odds on what a person is most likely to do next, suggests ...

#### Sleep makes it possible for babies to associate words with content—and not with noise

August 8, 2017
While babies sleep, astonishing processes take place in their brains. Scientists at the Max Planck Institute for Human Cognitive and Brain Sciences (MPI CBS) in Leipzig observed that babies succeed in associating a meaning ...

#### Heartbeats could hold the key to understanding babies' inner world

August 8, 2017
Scientists from Royal Holloway, University of London have found that babies as young as five months are sensitive to their own heartbeats, and their research could pave the way to better understanding disorders such as anxiety, ...

#### Study with infants suggests color categorization is biological

May 9, 2017
(Medical Xpress)—A team of researchers with members from the University of Sussex and the University of California has found evidence that suggests color categorization in humans is biological rather than learned. In their ...

#### Watching the world in motion, babies take a first step toward language

September 15, 2011
Watching children on the playground, we see them run, climb, slide, get up, and do it all again. While their movements are continuous, we language-users can easily divide them up and name each one. But what about people—babies—who ...

#### Element of surprise helps babies learn

April 2, 2015
Infants have innate knowledge about the world and when their expectations are defied, they learn best, researchers at Johns Hopkins University found.

## Recommended for you

#### Exposure to farmyard bugs reduces immune overreaction found in childhood asthma

September 24, 2018
Treating new born mice with farmyard microbes reduces wheezing and inflammation in the airways, by 'taming' their immune systems.

#### Stepfathers' 'Cinderella effect' challenged by new study

September 24, 2018
Long-held assumptions that stepfathers are far more likely to be responsible for child deaths than genetic parents have been challenged by researchers at the University of East Anglia (UEA).

#### Fatty acids can slow down an overheated immune system

September 21, 2018
Sometimes, the immune system mistakenly attacks the body's healthy tissue by responding to infections that do not exist. This causes chronic inflammation and leads to diseases including lupus (SLE), and this is what happens ...

#### Study shows surprise low-level ozone impact on asthma patients

September 21, 2018
A new study led by UNC School of Medicine researchers indicates that ozone has a greater impact on asthma patients than previously thought. The study, published in the Journal of Allergy and Clinical Immunology, recruited ...

#### Patient-centered visual aid helps physicians discuss risks, treatments with parents

September 21, 2018
A series of illustrations and charts designed as decision aids for parents of children with minor head injuries helped them communicate with emergency medicine physicians and make informed decisions about their child's care, ...

#### Fish-rich diets may boost babies' brain development

September 20, 2018
Women could enhance the development of their unborn child's eyesight and brain function by regularly eating fatty fish during pregnancy. This is the suggestion from a small-scale study led by Kirsi Laitinen of the University ...