People in different cultures make different assumptions about the people around them, according to an upcoming study published in Psychological Science, a journal of the Association for Psychological Science. The researchers studied the brain waves of people with Caucasian and Asian backgrounds and found that cultural differences in how we think about other people are embedded deep in our minds. Cultural differences are evident very deep in the brain, challenging a commonsense notion that culture is skin deep.

For decades, psychologists believed that it’s natural for humans to see behaviors and automatically link them to personality. “For example, when you see somebody giving a seat to an old man in a train, you might jump to the conclusion that that person is very nice and kind,” says Shinobu Kitayama, of the University of Michigan. He co wrote the new study with Jinkyung Na. “But the behavior may be motivated by some other things. For example, maybe his boss at work may be in that same train, or there might be very strong social norms” that led to the younger man giving up his seat.

Past research has found that Americans are more likely to assume the person is nice, while Asians are more likely to consider social factors. Psychologists explained this by saying that making the assumption about personality is automatic; everybody does it, but Asians continue on from there, taking the second step of considering social factors.

But Kitayama and Na found differently. In their study, they had European-American and Asian-American students do an exercise in which they were told to memorize faces and behaviors. For example, they might see a woman’s face and read that Julie checks the fire alarms every night before bed. In a second phase of the experiment, the researchers found evidence that European-Americans had made an inference about Julie’s personality during the first memory task, while Asian-Americans had not.

One way they did this was actually measuring participants’ brain wave patterns. For example, if a European-American had seen the information above and later was shown Julie’s face, immediately followed by personality traits, such as courageous or brave, that clearly go against the traits implied by her behavior, a particular flash of brain activity would happen within a split second, demonstrating “surprise.” But in Asian-Americans, such a brain activity didn’t happen because they hadn’t assumed from Julie’s behavior that she was cautious or neurotic.

This shows that there are real cultural differences in how people perceive others, Kitayama says. “It isn’t just a matter of intentional deliberate effort, but the immediate response to somebody’s behavior appears to be very different.”

“We often feel that culture is like clothes; you strip them off, and we are all humans,” Kitayama says. “There’s some truth to that, but studies like this begin to demonstrate that culture can go much deeper. What appears to be a natural being, or a human mind, may be culturally shaped or formed.”