I find it difficult to take these social science studies seriously these days. It's often impossible to separate cause, effect and correlation.
People with poor cognition are more likely to socially isolate themselves (due to rejection by peers and/or trouble fitting in due to their unconventional thinking styles). Also, cognitive tests were typically designed by psychologists and other social scientists so there are likely to be biases in the kinds of intelligence that they measure; they likely favor people who are (on average) more social and more conventional thinkers like themselves.
The other way around is true as well. Smart people sometimes get rejected by peers and some often prefer solitude. Solitude doesn't need to manifest in loneliness though. But you rarely meet a luminary that doesn't need a lot of alone time or is unhappy with a lot of it.
There were studies that people generally get happier with more socialization with the exception of smart people that get unhappy with too much of it. But there are also exception to this rule. You might prefer alone time and you might still be dumb as a brick.
People with poor cognition are more likely to socially isolate themselves (due to rejection by peers and/or trouble fitting in due to their unconventional thinking styles). Also, cognitive tests were typically designed by psychologists and other social scientists so there are likely to be biases in the kinds of intelligence that they measure; they likely favor people who are (on average) more social and more conventional thinkers like themselves.