When kids say "the darnedest things," it's often in response to something they heard or saw. This sponge-like learning starts at birth, as infants begin to decipher the social world surrounding them long before they can speak.

Now researchers at the University of Washington have found that children as young as 15 months can detect anger when watching other people's social interactions and then use that emotional information to guide their own behavior.

The study, published in the October/November issue of the journal Cognitive Development, is the first evidence that younger toddlers are capable of using multiple cues from emotions and vision to understand the motivations of the people around them.

"At 15 months of age, children are trying to understand their social world and how people will react," said lead author Betty Repacholi, a faculty researcher at UW's Institute for Learning and Brain Sciences and an associate professor of psychology. "In this study we found that toddlers who aren't yet speaking can use visual and social cues to understand other people -- that's sophisticated cognitive skills for 15-month-olds."

The findings also linked the toddlers' impulsive tendencies with their tendency to ignore other people's anger, suggesting an early indicator for children who may become less willing to abide by rules.

"Self-control ranks as one of the single most important skills that children acquire in the first three years of life," said co-author Andrew Meltzoff, co-director of the institute. "We measured the origins of self-control and found that most of the toddlers were able to regulate their behavior. But we also discovered huge individual variability, which we think will predict differences in children as they grow up and may even predict important aspects of school readiness."

In the experiment, 150 toddlers at 15 months of age -- an even mix of boys and girls -- sat on their parents' laps and watched as an experimenter sat at a table across from them and demonstrated how to use a few different toys.

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Each toy had movable parts that made sounds, such as a strand of plastic beads that made a rattle when dropped into a plastic cup and a small box that "buzzed" when pressed with a wooden stick. The children watched eagerly -- leaning forward and sometimes pointing enthusiastically.

Then a second person, referred to as the "emoter," entered the room and sat down on a chair near the table. The experimenter repeated the demonstration and the emoter complained in an angry voice, calling the experimenter's actions with the toys "aggravating" and "annoying."

After witnessing the simulated argument, the children had a chance to play with the toys, but under slightly different circumstances. For some, the emoter left the room or turned her back so she couldn't see what the child was doing. In these situations, toddlers eagerly grabbed the toy and copied the actions they had seen in the demonstration.

In other groups, the angered emoter maintained a neutral facial expression while either watching the child or looking at a magazine. Most toddlers in these groups hesitated before touching the toy, waiting about four seconds on average. And when they finally did reach out, the children were less likely to imitate the action the experimenter had demonstrated.

The study didn't factor in how much previous conflict children had seen at home or elsewhere, such as arguing parents or violent television shows. But Repacholi speculated that an emotionally charged home environment could make some children desensitized to anger, or others could become hypersensitive to it and overreact.

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The researchers also wondered if the children's temperament played a role. They had parents fill out the Early Childhood Behavior Questionnaire, which uses questions like "How long does your child stop and think before making decisions?" to measure impulsivity.

The higher the score for impulsivity, the researchers found, the more likely the toddlers were to perform the forbidden actions when the anger-prone adult was watching them.

Repacholi and Meltzoff are doing a follow-up study with the toddlers, who are now school-aged, to see if their behaviors as 15-month-olds predicts their later ability to control their own behavior.

"Ultimately, we want kids who are well regulated, who can use multiple cues from others to help decide what they should and shouldn't do," Repacholi said.