Review
Perceived social isolation and cognition

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Social species, from Drosophila melanogaster to Homo sapiens, fare poorly when isolated. Homo sapiens, an irrepressibly meaning-making species, are, in normal circumstances, dramatically affected by perceived social isolation. Research indicates that perceived social isolation (i.e. loneliness) is a risk factor for, and may contribute to, poorer overall cognitive performance, faster cognitive decline, poorer executive functioning, increased negativity and depressive cognition, heightened sensitivity to social threats, a confirmatory bias in social cognition that is self-protective and paradoxically self-defeating, heightened anthropomorphism and contagion that threatens social cohesion. These differences in attention and cognition impact on emotions, decisions, behaviors and interpersonal interactions that can contribute to the association between loneliness and cognitive decline and between loneliness and morbidity more generally.

Introduction

The health, life and genetic legacy of members of social species are threatened when they find themselves on the social perimeter. Social isolation decreases lifespan in the fruit fly [1]; promotes obesity and Type 2 diabetes in mice [2]; exacerbates infarct size and edema and decreases post-stroke survival rate following experimentally induced stroke in mice [3]; promotes activation of the sympatho-adrenomedullary response to an acute immobilization or cold stressor in rats [4]; delays the effects of exercise on adult neurogenesis in rats [5]; decreases open field activity, increases basal cortisol concentrations and decreases lymphocyte proliferation to mitogens in pigs [6]; increases the 24 h urinary catecholamines levels and evidence of oxidative stress in the aortic arch of rabbits [7]; and decreases the expression of genes regulating glucocorticoid response in the frontal cortex of piglets [8]. Humans, born to the longest period of abject dependency of any species and dependent on conspecifics across the lifespan to survive and prosper, do not fare well either, whether they live solitary lives or simply perceive that they live in relative isolation (Box 1).

Perceived social isolation, known more colloquially as loneliness, was characterized in early scientific investigations as ‘a chronic distress without redeeming features’ (p. 15) [9]. Recent research suggests that the social pain of loneliness evolved as a signal that one's connections to others are weakening and to motivate the repair and maintenance of connections to others that are needed for our health and well being and for the survival of our genes (Box 2) [10]. Experimental, cross-sectional and longitudinal studies are beginning to elucidate the various ways in which loneliness is related to, and in some cases affects, human information processing.

Section snippets

Cognitive capacities

Human social processes were once thought to have been incidental to learning and cognition, whereas the social complexities and demands of primate species are now thought to have contributed to the evolution of the neocortex and various aspects of human cognition. Consistent with this reasoning, human toddlers and chimpanzees have similar cognitive skills for engaging the physical world but toddlers have more sophisticated cognitive skills than chimpanzees for engaging the social world [11];

Executive functioning

Executive functioning includes the capacity to control one's attention, cognition, emotion and/or behavior to better meet social standards or personal goals, that is, to self-regulate. Early evidence from young adults who performed a dichotic listening task suggested that attentional regulation was poorer in lonely than nonlonely individuals [24]. Participants were asked to identify the consonant-vowel pair presented in the left or right ear. Typically, performance shows a right-ear advantage

Colorations of cognition

Experimental manipulations of loneliness not only impair executive functioning but also produce higher negative mood, anxiety, anger and depressive symptomatology [30]. An experience sampling study, in which participants were beeped randomly nine times per day for seven days, confirmed that the social interactions of lonely, in contrast to nonlonely, individuals were more negative and less satisfying and such interactions contributed subsequently to more negative moods and interactions [31].

Social cognition

The brains of lonely, in contrast to nonlonely, individuals are on high alert for social threats, so lonely individuals tend to view their social world as threatening and punitive (Box 3). Experimental manipulations of loneliness not only cause people to feel more anxious, fear negative evaluation and act more coldly toward others [30], but it also causes them to feel colder as assessed by ratings of room temperature [42]. Lonely individuals also tend to form more negative social impressions of

Contagion

Loneliness is typically investigated as an individual factor, but because perceived and objective isolation can be differentiated, loneliness can also vary within and across groups. Network linkage data from the population-based Framingham Heart Study were used to trace the topography of loneliness in social networks and the path through which loneliness spreads through these networks [52]. Results indicated that loneliness occurs in clusters within social networks, is disproportionately

Conclusion

Cognition has been regarded as a quintessential individual activity. Mental representations and processes were rendered testable in the dawn of the cognitive sciences by virtue of reverse engineering: mathematical and computer models were created that specified stimulus inputs, information processing operations that acted on and transformed these inputs to produce and change representational structures, and information processing operations that led to observable responses. Computers today are

Disclosure statement

This research was supported by the National Institute of Aging Program Project Grant No. PO1 AG18911 & RO1 AG034052-01 and by a grant from the John Templeton Foundation. These funding sources had no role or influence in the preparation of this review.

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