We all tend to feel isolated, rejected, or frustrated when we’re being ignored or misunderstood. Social isolation can induce feelings of loneliness and cause our brains to become alert to threats and the possible danger of strangers. According to a recent study, published in the journal Cortex, lonely people’s brains differ from those of non-lonely people, as regions that make them highly vigilant become more active in social situations.

When we feel socially isolated, our brains automatically switch into self-preservation mode, making us more abrasive and defensive in the face of supposed social danger, even when it isn’t actually there, according to Psychology Today. When we buy into these false perceptions of being lonely, we become more sensitive to more criticisms and tend to brush off compliments — all because we’re focused on our own welfare.

Stephanie and John Cacioppo, married researchers from the University of Chicago, and leading experts on the psychology and neuroscience of loneliness, wrote in their study: “Our evolutionary model of the effects of perceived social isolation (loneliness) on the brain as well as a growing body of behavioral research suggests that loneliness promotes short-term self-preservation, including an increased implicit vigilance for social, in contrast to nonsocial, threats.”

The pair, and their colleague Stephen Balogh, sought to explore the brain differences between lonely people and non-lonely people when it comes to perceiving social and nonsocial threats. A loneliness questionnaire was distributed to 38 very lonely people and 32 people who didn’t feel lonely. For the study, loneliness was defined as the subjective feeling of isolation as opposed to the number of friends or close relatives a person has.

An electrode array of 128 sensors was placed on each of the participants’ heads to record their brain waves using electroencephalography (EEG) — a technique that measures brain activity changes over short time periods. The researchers also conducted a Stroop Test, in which participants were asked to focus on a word’s color on a computer screen, not its name. Participants were asked to quickly type the color of the word. This test was meant to assess how participants' brains worked when it came to automatic and subconscious influences.

The test included some words that were social and positive, like “belong” and “party,” while some were social and negative, like “alone” and “solitary.” Other words were emotionally positive but nonsocial, such as “joy,” and others were nonsocial and emotionally negative, such as “sad,” according to New York magazine. This helped the researchers determine  how the participants’ brains responded to the sight of negative words that were social in nature, when compared to those that were nonsocial.

The researchers analyzed participants’ brain waves as they looked at different word types, and as their brains entered discrete microstates — periods of relative stability when a consistent pattern of brain regions is activated. When a microstate changed, it indicated the participant entered a new pattern of thought.

After a word was shown on the screen, lonely people’s brains went into a series of three discrete microstates that were identical regardless of whether a negative word was socially relevant or not. After this, their brains entered a microstate that specifically responded to socially negative words, with activation in areas involved with controlling attention. This led lonely people to become highly vigilant.

By comparison, the brains of non-lonely people responded with the same microstates to both social and nonsocial negative words, albeit for about a quarter second longer than the lonely group. This is instrumental because it shows lonely people’s brains are conditioned to tune into social threats faster than what would be considered normal. Researchers believe lonely people’s heightened vigilance to social threats is rooted in their subconscious.

The test was meant to be fast enough that participants wouldn’t pay much attention to the words’ meanings. However, it found that the lonely people were able to pick up on the differences between socially threatening words like “hostile” and negative nonsocial words like “vomit” more quickly than non-lonely people. This suggests lonely people are subconsciously looking out for negativity.

This study coincides with previous research that found brain activity in lonely people is consistent with self-preservation. In a 2009 study published in the journal Trends in Cognitive Sciences, brain scans found that when people felt lonely their brains became more active in response to images of another person in distress. Their brains also became less activated in an area involved with understanding others people’s emotions and recognizing situations from their perspectives.

As humans we thrive on social connection. Despite how many Facebook friends or Twitter followers we have, we can still be lonely and fall into social isolation. Surrounding ourselves with others and focusing on close relationships helps us live a happy and healthy life.

Sources: Balogh S, Cacioppo JT, and Cacioppo S. Implicit attention to negative social, in contrast to nonsocial, words in the Stroop task differs between individuals high and low in loneliness: Evidence from event-related brain microstates. Cortex. 2015.

Cacioppo JT and Hawkley LC. Perceived social isolation and cognition. Trends Cogn. Sci. 2009.