Dr. Rony Paz the Weizmann Institute and Offir Laufer, a student, had study subjects listen to a series of tones composed of three different notes. After hearing one note, they were told they had earned a certain sum; after a second note, they were informed they had lost some of their money; and a third note was followed by the message that their bankroll would remain the same.
The researchers found when a note was tied to gain, or at least to no loss, the subjects improved over time in a learned task, but when they heard the "lose money" note, they got worse at telling one note from the other.
Brain scans revealed an emotional aspect, in that the amygdala -- the part of the brain tied to emotions and reward -- was strongly involved.
"The evolutionary origins of that blurring of our ability to discriminate are positive: If the best response to the growl of a lion is to run quickly, it would be counterproductive to distinguish between different pitches of growls," Paz said in a statement. "Any similar sound should make us flee without thinking. Unfortunately, that same blurring mechanism can be activated today in stress-inducing situations that are not life-threatening -- like losing money -- and this can harm us."