During the study, the researchers found that participants who heard personal insults while seated exhibited brain activity linked to so-called "approach motivation", that is the desire to approach and explore something.
However, this urge disappeared when students took their insults lying down, despite their anger.
"In the upright or leaning forward state one might be more likely to attack," New Scientist quoted lead researcher Eddie Harmon-Jones, a cognitive scientist at Texas A and M University in College Station, as saying.
"Maybe in the reclining state you're more likely to brood," he added.
In the study, the researchers asked the participants to select a hot-button issue, such as abortion or public smoking, and write a brief essay on their stance.
The research team later played a voice recording of someone criticizing the intelligence, likeability and logical skills of the essayist.
"People get angry in response to this kind of feedback," said Harmon-Jones.
The people who heard these insults while on their backs were as angry as volunteers who were seated.
However, EEG recordings showed that those who were upright, a brain region called the right prefrontal cortex was more active than its counterpart in the brain's left hemisphere.
Previous studies have shown a link between the activation, anger and approach motivation.
However, those who heard their insults while lying down exhibited EEG patterns no different from subjects who got slightly positive reviews.
Harmon-Jones believes lying down could affect how the brain handles other emotions, such as desire and happiness.
"It's unknown how much of an effect this has, but this study suggests that people should start looking to see if body position is affecting processing in other types of experiments," said Harmon-Jones says, noting that most of our decisions are made while we're upright, not lying down.
The findings appear in journal Psychological Science.