Have you ever caught a baby's eyes and suddenly felt judged? New research suggests that feeling may not be entirely imaginary.
If you've done something a baby disapproves of, they might be using their gaze to single you out.
A series of experiments, conducted among 8-month-old infants, has now found evidence that preverbal children are moral third-party observers.
When witnessing an act of aggression – played out by simple animations on a computer screen – infants in the study focused their attention more on the aggressor in the aftermath.
If the attacker was stared at long enough by the baby, an eye tracking program connected to the computer made the character disappear.
In other words, the babies were given the ability to vanquish unwelcome animations with only their eyes.
Some psychologists argue this unwavering stare is a sign of intent to punish: The antisocial behavior of the attacker prompts the babies to focus on the attacker until they go away.
Given that the infants were not able to express themselves in words, however, the authors can't be sure the babies intended to punish the aggressor. Their fixed attention could also be an expression of caution in the face of a volatile character, or an expectation that the attacker would receive some consequence for their action.
Decision-making in preverbal children is extremely difficult to measure because communication is so limited. Previous studies have found toddlers as young as 19 months are willing to act as third-party judges, taking treats away from those who are actively antisocial.
A stare down is a much less developed form of punishment, but if the authors are right, it could be the earliest sign of a moral compass in children, one that is possibly more inherent than learned.
"Morality is an important but mysterious part of what makes us human," explains psychologist Yasuhiro Kanakogi from Osaka University in Japan.
"We wanted to know whether third-party punishment of antisocial others is present at a very young age, because this would help to signal whether morality is learned."
A series of experiments was used to explore why 8-month-old babies might be more focused on those who commit a social faux pas.
Physical aggression in the form of hitting was used in the study because it is one of the most obvious social missteps known to infants.
Other research has shown early infants can tell the aggressor from the victim in incidents of hitting. They also show aversion to this sort of behavior.
The experiments took place on a computer screen. Infants were sat in front of the screen and shown two animated characters. Their eyes were tracked during the experiment, and if they stared long enough at a character, it would be destroyed.
Then, the infants were shown a video of one of the characters hitting the other. At the end of the video, the babies were once again shown both characters side by side. With the gaze-tracking system, the babies vanquished significantly more aggressors than victims.
The experiment was replicated and repeated several times with different variations, including a soft hit from a falling object, and an equal chance of both characters being punished regardless of which the child looked at. This was to make sure the kids didn't merely prefer the aggressor characters more, or that they were watching to make sure the aggressor got punished.
The findings ultimately suggest young children are doling out punishment for violent social interactions specifically.
"The results were surprising. We found that preverbal infants chose to punish the antisocial aggressor by increasing their gaze towards the aggressor," says Kanakogi.
"The observation of this behavior in very young children indicates that humans may have acquired behavioral tendencies toward moral behavior during the course of evolution. Specifically, the punishment of antisocial behavior may have evolved as an important element of human cooperation."
The study was published in Nature Human Behaviour.