By understanding the way the brain reacts to outside stimuli, psychologists hope to find more effective treatments for depression and emotional problems.

Researchers already knew that people tend to prefer familiar stimuli, because repeated exposure to situations or objects creates a sense of security and mental attachment, and repeated exposure to situations or objects will increase the affinity a person has toward it.

According to UCSD psychology professor and project leader Piotr Winkielman, researchers have discovered that familiarity preference depends on whether someone is feeling happy or sad at the same time they are being exposed to the familiar or non-familiar stimulus.

“It contributes to a better understanding of our emotions, and that’s a good thing because we want to improve people’s emotional functioning,” Winkielman said. “We want to help people feel less sad, or if they feel sad, we want to help them deal with this. It’s basically a better understanding of how emotions change our judgments.”

In the one-year experiment that began in 2008, researchers repeatedly exposed UCSD student participants to random dot patterns that resembled star constellations. Then, to put the subjects in a good or a bad mood, psychologists asked students to think of happy or sad memories.

With these memories in mind, subjects were once again exposed to the patterns, and their emotional and psychological responses were measured through both self-reported ratings and involuntary physiological indicators of emotion. For example, skin conductors were attached to the subject’s skin to detect sweat and facial electrodes to detected spontaneous frowns and smiles.

As the researchers predicted, the subjects who were thinking of depressing memories demonstrated a preference for the familiar through a higher rate of involuntary smiling.

By contrast, those who thought of happy moments while viewing the stimuli showed a greater positive response to the unfamiliar, demonstrating that those who were happy preferred novel things and new experiences to routine ones.

This helps explain a wide range of social situations, from a consumer’s decision to buy one product over another, to the way a person forms an impression of their environment and chooses a political candidate, to the understanding of how children develop.

Given its extensive applications from marketing to political campaigns to parenting, this knowledge of basic human psychology can give greater insight into our decision-making processes.

“There’s a lot of interest in everyday persuasion contexts, from trying to help people respond to products or political messages,” Winkielman said. “Also, in some clinical contexts, you want to understand how people who are depressive change their preferences for familiar or novel things or people who are manic who have highly positive moods — how they change preferences.”

The research team, which also consists of graduate student Troy Chenier and scientists from the University of the Netherlands, will continue to study how emotions influence how humans think, perceive and make choices, as well as how these processes manifest in the body and the brain.

Readers can contact Regina Ip at [email protected].