The Elegant Robert Zajonc
The great social psychologist Robert Zajonc came up with elegant explanations for three very important phenomena.
1) The literature on physiological arousal and task performance was a mess, with some people finding performance improvement with greater arousal and some people finding performance decrement. Zajonc showed that, for the simplest tasks, the greater the arousal the greater the improvement—because arousal was amplifying a simple, overlearned response. For more complex tasks, arousal worsened task performance—because arousal was simultaneously multiplying many possible alternative, and competing, responses.
2) The earlier in the sibship a person is born the higher the IQ on average. This had long been known but Zajonc offered the most plausible explanation to date. The firstborn comes into a world where the average IQ is 100 (mother) + 100 (father) + 0 (self)/3 = 83.33. The second child is born into a family with a lower average IQ because the average 100 IQ of each parent is diluted not only with the second child’s own zero IQ but with the first child’s IQ, which, unless that child is adult, is less than 100 on average. The larger the number of children the worse the average intelligence of the environment in which intellectual development takes place.
3) Zajonc showed that "mere familiarity" with an object of apparently any kind increases its attractiveness. This is true of photographs of people, of snatches of a melody, of Turkish words (for monolingual English speakers) and of Chinese characters (for people ignorant of Chinese languages). Unless the initial attractiveness of a stimulus is negative—and sometimes even then—preference for the stimulus increases with exposure. Zajonc discovered this fact decades ago but never could come up with a plausible explanation for it—nor could anyone else. Toward the end of his life Zajonc came up with an extremely simple explanation in terms of reinforcement theory. Every time we encounter a stimulus that is not followed by punishment of some kind a minor reward is experienced. The more the exposures to the (unpunished) stimulus the greater the reward associated with it and hence the greater its attractiveness.