Loneliness expert John Cacioppo was the late director of the University of Chicago's Center for Cognitive and Social Neuroscience. In this clip, he explains the difference between objective and perceived isolation, what consequences isolation brings, and why it should be considered a problem.
Humans are fundamentally a social species, and social species, by definition, create social structures (e.g. families, pairs, villages, institutions). These structures help us survive, reproduce, and care for our offspring. One way to study social isolation is to look at what the lack of these social structures do to our brain and biology.
In the clip, Cacioppo distinguishes between perceived social isolation (also called loneliness) and objective social isolation. Objective social isolation is the result of having few friends or no family. Perceived social isolation (loneliness), on the other hand, can be felt even in a social context; for example, one can be at a family dinner and still feel lonely. Although objective, social isolation can predict loneliness, Cacioppo finds that perceived social isolation is more closely related to the quality rather than the quantity of social interactions. Accordingly, perceived social isolation predicts various outcomes above and beyond what is predicted by objective isolation.
Loneliness affects how the brain perceives the world. It makes the brain become alert, which in turn means that we sleep worse. People who feel lonely also tend to feel shyer, have poorer social skills, feel sadder, feel more hostile, and have a more negative mood. Research has shown that these are all consequences of loneliness. If research participants are made to feel lonely, they also become sadder, their mood lowers, and so forth. In fact, the effect of isolation on mortality is four times larger than obesity, and it is more prevalent. Cacioppo argues that social isolation and loneliness are major social issues.