Your mother may have taught you never to judge a book by its cover, but according to science, your mother was wrong.

According to a new study from Cornell University psychologists, the assumption someone makes about a person when they first meet, or the first impression, is usually the correct one. Another study also concluded that once someone draws a first opinion about someone, it is pretty difficult to change their opinion later on, Live Science reported Tuesday.

"Despite the well-known idiom 'not to judge a book by its cover,' the present research shows that such judgments about the cover are good proxies for judgments about the book- even after reading it," psychologist Vivian Zayas, from Cornell, said in a statement obtained by Live Science.

The studies were presented at the annual meeting for the Society for Personality and Social Psychology in Austin, Texas.  

Psychologists presented a picture of a person to the participants and asked them to make a quick assessment about how he or she would feel if they came in contact with that person.

The person in the picture and the participant then met with each other a month later, Live Science reported. Zayas was shocked to find that the judgments the participants made about the other person, such as whether or not they would like them, were accurate, Live Science reported.

In another experiment, participants were asked to make a distinction between trustworthy and untrustworthy faces. The faces came with labels that described actions that could be considered trustworthy, such as volunteering at a hospital, Live Science reported. The untrustworthy faces came with labels such as thief.

Psychologists found that the participants tended to remember those with untrustworthy faces more than they remembered those with trustworthy ones. Also, when the participants were asked to make a judgment based on the faces alone and not their description, the participants were able to accurately recall both trustworthy and untrustworthy people.

The study concluded that whenever someone sees another person, their initial judgments about them come to mind, psychologist Nicholas Rule told Live Science.

"Their face is a constant reminder to us of that initial impression," Rule said. Rule added that once someone gets to know another person over time, the first impression might not matter anymore if they differ from how they really are. Nevertheless, initial judgments appear to stick, Live Science reported.

"It goes to show that perhaps the opportunities that one gets in life can be very much shaped by one's face," Rule told Live Science.