Traditionally, being “book smart” has been viewed as a valuable predictor of success (Sternberg, 2000). However, being competent at conventional intelligence tests or good at schoolwork is not a guarantee that one can adjust to different environments and succeed in the real world. For that, a person also needs social intelligence. In this chapter, we discuss what social intelligence is and how it relates to other kinds of intelligence, discuss then the role of nonverbal communication in social intelligence, and then discuss how it fits into a broader concept of adaptive intelligence, or intelligence as adaptation to the environment.
Definition of Social Intelligence
The definition of social intelligence has evolved over time (see Kihlstrom & Cantor, 2011, in press, for a much more detailed history of this evolution). Social intelligence was first mentioned and described by Dewey (1909) as the ability to observe and understand social circumstances as part of the ultimate goal of moral education. Later on, the concept of social intelligence was included in one of Thorndike’s (1920) three kinds of intelligences and defined as “the ability to understand and manage men and women, boys and girls—to act wisely in human relations” (p. 228). (The other two aspects of intelligence were abstract and mechanical intelligence.) Wedeck (1947) went further, describing it as a “psychological ability to judge correctly the feelings, moods, and motivations of individuals” (p. 133). Likewise, Wechsler (1958) indicated that social intelligence is a “facility in dealing with human beings” (p. 8). Later on, nonverbal cues were included in the conceptualization of social intelligence: “the ability to understand the thoughts, feelings, and intentions of other people as manifested in discernible, expressional cues” (O’Sullivan, Guilford, & deMille, 1965, p. 6). Barnes and Sternberg (1989) added to this definition by emphasizing the importance of information-decoding skills. They further defined social intelligence as “the ability to accurately decode social information” (p. 263). They found, as did Sternberg and Smith (1985), that social intelligence as the ability to decode is relatively independent of measures of general intelligence. However, different social-intelligence tests, such as discerning whether a photograph is of a real couple or a fake couple (i.e., an unconnected couple posing as a real couple) and discerning who of two people is the supervisor and who is the supervisee, are also relatively independent of each other. On average, women performed better than men on the tests. Finally, Daniel Goleman has viewed social intelligence as emerging from the interaction of people, in contrast to emotional intelligence, which can emerge from just a single individual (Goleman, 1995, 2006).
The first to integrate social intelligence fully into a complete model of intelligence was J. P. Guilford (1967; Guilford & Hoepfner, 1971). Guilford suggested that intelligence could be understood, metaphorically, in terms of a cube crossing five contents, six products, and five operations. The total number of abilities was 5 × 6 × 5, or 150 (or 120, in the original version of the model). Relevant to social intelligence was what Guilford referred to as “behavioral” content. For example, one ability was evaluation (operation) of behavioral (content) systems (product). The behavioral facets of the theory were tested through items similar to those on tests generated by other models.
Howard Gardner later integrated multiple facets of intelligence into his conceptualization of multiple intelligences. He created a theory of eight multiple intelligences, which included allegedly independent intelligences such as linguistic, logical-mathematical, spatial, bodily-kinesthetic, musical, and naturalist. Two further intelligences, however, could be considered as relevant to the full concept of social intelligence: interpersonal intelligence and intrapersonal intelligence (Gardner, 1983, 2011). This theory was partly informed by Walker and Foley (1973), who went beyond decoding skills to include encoding communication skills in their definition of social intelligence: “the ability to understand people and to act wisely in social situations” (p. 839). Similarly, Marlowe (1986) defined social intelligence as “the ability to understand the feelings, thoughts, and behaviors of persons, and to act appropriately upon that understanding” (p. 56). This definition combined the interpersonal and intrapersonal components from Gardner’s multiple intelligences theory and is consistent with Sternberg’s practical intelligence (Romney & Pyryt, 1999).
In Sternberg’s theory of successful intelligence (1997, in press-b), social intelligence is a part of practical intelligence. Practical intelligence is a function of tacit knowledge (Polanyi, 1976), or what one needs to know to succeed in life that is not explicitly taught and that often is not even verbalized. For example, typically, no one teaches a child how to encode or decode nonverbal cues or how to recognize when another person is extremely upset. One learns from experience.
What are some of the main psychometric and other properties of practical intelligence (Hedlund, in press; Hedlund et al., 2003; Hedlund, Wilt, Nebel, Ashford, & Sternberg, 2006; Sternberg, 2009, 2010; Sternberg et al., 2000; Sternberg & Hedlund, 2002; Wagner, 2011)? First, practical intelligence can be measured reliably. In particular, when measures of managing oneself, managing others, and managing tasks are included in a practical-intelligence test, the measures show high internal consistency within category and high correlations between categories. Second, measures of practical intelligence tend to show relatively weak correlations with typical measures of general (cognitive) intelligence. In one case, the correlation of practical with general intelligence was negative (Sternberg et al., 2001). Third, measures of practical intelligence provide significant incremental validity over conventional intelligence tests in predicting both academic and extracurricular performance as well as in predicting on-the-job performance (Sternberg, 2010). Fourth, practical intelligence can be statistically differentiated not only from academic aspects of intelligence but also from various aspects of personality (Sternberg & Hedlund, 2002). Fifth, measures of practical intelligence can predict success in military leadership independently of measures of general intelligence (Horvath et al., 1999). Sixth, practical-intelligence measures, at least within a given domain (such as for salespeople or business executives or academics), tend to be moderately to highly correlated with each other (Sternberg et al., 2000). Finally, factor analyses reveal practical intelligence to be a separate factor from general intelligence, except when practical intelligence is measured through multiple-choice format. When it is measured by multiple-choice items, it comes closer to general intelligence (Sternberg, Wong, & Sternberg, 2019).
Sternberg and his colleagues further investigated social intelligence in the context of style of conflict resolution (Sternberg & Dobson, 1987; Sternberg & Soriano, 1984). Problems were presented in the form of narratives that posed interpersonal, interorganizational, or international conflicts. Participants were asked to evaluate solutions that were of different kinds, such as resolving conflicts by physical threats, economics threats, seeking third-party intervention, and so forth. The style of conflict resolution that was most highly correlated with general intelligence was a step-down style, whereby the protagonist tried to resolve the conflict by means that involved lessening rather than heightening tensions.
Should Social Intelligence Be Separated from General Intelligence?
The concept of social intelligence was not explicitly included in most definitions of human intelligence until Sternberg (1997) included it as part of practical intelligence—an ability to use knowledge and skills to solve problems in daily life—in his triarchic theory of successful intelligence. Yet the question of whether social intelligence should be independent from general intelligence has been long debated. Wechsler (1958), for instance, claimed that social intelligence is “just general intelligence applied to social situations” (p. 75). In contrast, Riggio, Messamer, and Throckmorton (1991) argued that social intelligence is a distinctive psychological construct and emphasized the necessity of distinguishing it from general intelligence.
Despite the efforts of scholars like Riggio, Messamer, and Throckmorton (1991), social intelligen...