In most psychological ivory towers there will be found an animal laboratory. The scientists who live there think of themselves as theoretical psychologists, since they obviously have no other rationalization to explain their extravagantly paid and idyllic sinecures. These theoretical psychologists have one great advantage over those psychological citizens who study men and women. The theoreticians can subject their subhuman animals, be they rats, dogs, or monkeys, to more rigorous controls than can ordinarily be exerted over human beings. The obligation of the theoretical psychologist is to discover general laws of behavior applicable to mice, monkeys, and men. In this obligation the .theoretical psychologist has often failed. His deductions frequently have had no generality beyond the species which he has studied, and his laws have been so limited that attempts to apply them to man have resulted in confusion rather than clarification.One limitation of many experiments on subhuman animals is the brief period of time the subjects have been studied. In the typical problem, 48 rats are arranged in groups to test the effect of three different intensities of stimulation operating in conjunction with two different motivational conditions upon the formation of an isolated conditioned response. A brilliant Blitzkrieg research is effected-the controls are per-1 This paper was presented as the presidential address of the Midwestern Psychological Association meetings in St. Paul, May 7, 1948.

Love is a wondrous state, deep, tender, and rewarding. Because of its intimate and personal nature it is regarded by some as an improper topic for experimental research. But, whatever our personal feelings may be, our assigned mission as psychologists is to analyze all facets of human and animal behavior into their component variables. So far as love or affection is concerned, psychologists have failed in this mission. The little we know about love does not transcend simple observation, and the little we write about it has been written better by poets and novelists. But of greater concern is the fact that psychologists tend to give progressively less attention to a motive which pervades our entire lives. Psychologists, at least psychologists who write textbooks, not only show no interest in the origin and development of love or affection, but they seem to be unaware of its very existence. The apparent repression of love by modem psychologists stands in sharp contrast with the attitude taken by many famous and normal people. The word "love" has the highest reference frequency of any word cited in Bartlett's book of Familiar Quotations. It would appear that this emotion has long had a vast interest and fascination for human beings, regardless of the attitude taken by psychologists; but the quotations cited, even by famous and normal people, have a mundane redundancy. These authors and authorities have stolen love from the child and infant and made it the exclusive property of the adolescent and adult. Thoughtful men, and probably all women, have speculated on the nature of love. From the developmental point of view, the general plan is quite clear: The initial love responses of the human being are those made by the infant to the mother or some mother surrogate. From this intimate attachment of the child to the mother, multiple learned and generalized affectional responses are formed. Unfortunately, beyond these simple facts we know little about the fundamental variables underlying the formation of affectional responses and little about the mechanisms through which the love of the infant for the mother develops into the multifaceted response patterns characterizing love or affection in the adult. Because of the dearth of experimentation, theories about the fundamental nature of affection have evolved at the level of observation, intuition, and discerning guesswork, whether these have been proposed by psychologists, sociologists, anthropologists, physicians, or psychoanalysts.

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Investigators from diverse behavioral fields have long recognized the strong attachment of the neonatal and infantile animal to its mother. Although this affectional behavior has been commonly observed, there is, outside the field of ethology, scant experimental evidence permitting identification of the factors critical to the formation of this bond. Lorenz (1) and others have stressed the importance of innate visual and auditory mechanisms which, through the process of imprinting, give rise to persisting following responses in the infant bird and fish. Imprinting behavior has been demonstrated successfully in a variety of avian species under controlled laboratory conditions, and this phenomenon has been investigated systematically in order to identify those variables which contribute to its development and maintenance [see, for example, Hinde, Thorpe, and Vince (2), Fabricius (3), Hess (4), Jaynes (5), and Moltz and Rosenblum (6)]. These studies represent the largest body of existent experimental evidence measuring the tie between infant and mother. At the mammalian level there is little or no systematic experimental evidence of this nature.Observations on monkeys by Carpenter (7), Nolte (8), and Zuckermann (9) and on chimpanzees by Kohler (10) and by Yerkes and Tomilin (11) show that monkey and chimpa velop strong ties to the that these affectional at persist for years. It is, c mon knowledge that form strong and persiste mothers.Although students fror tific fields recognize this ment, there is considerab about the nature of its de its fundamental underlyii A common theory amon sociologists, and anthrop of learning based on d This theory proposes th attachment to the moth the association of the me form with the alleviation mary drive states, parti and thirst. Thus, throug fection becomes a self-s rived drive (12). Psycho; other hand, have stressed of various innate needs, to suck and orally pos, (2), or needs relating to ment, temperature (13) to the mother (14).The paucity of experin concerning the developr tional responses has led to derive their basic h, deductions and intuitions servation and analysis o reports. As a result, the ; vational evidence is oftei SCIENCE preconceived theoretical framework. An exception to the above generalization is seen in the recent attempt by Bowlby (14) to analyze and integrate the avail-_S able observational and experimental evidence derived from both human and subhuman infants. Bowlby has concluded ,Y that a theory of component instinctual responses, species specific, can best account for the infant's tie to the mother.?nt He suggests that the species-specific responses for human beings (some of these responses are not strictly limited to human beings) include contact, clinging, .nn sucking, crying, smiling, and following. He further emphasizes that these responses are manifested independently of primary drive reduction in human and subhuman infants. nzee infants deThe absence of experimental data ir mothers and which would allow a critical evaluation tachments may of any t...

Previous studies have reported that the maternal behavior of rhesus monkey females who themselves were reared without mothers ("motherless mothers") is generally inadequate and often abusive. The present study examined the maternal competency of SO such subjects with respect to the variables of rearing environment, age at first social contact, sex of offspring, age at first delivery, parity, and duration of exposure to previous offspring. The results suggested that physical contact with conspecifics, either with peers prior to adulthood or with their own infants immediately after birth, greatly reduced the probability that motherless mothers would be inadequate maternally.Researchers who have studied the consequences of social deprivation in rhesus monkeys are in virtual agreement that social isolation or restriction imposed early in life has devastating, and often permanent, effects on the social development of monkeys. As adults, monkeys reared for at least the first 6 months in physical isolation from conspecifics have been reported to exhibit anomalies in home-cage behavior (Cross & Harlow, 196S;Suomi, Harlow, & Kimball, 1971), in adaptation to novel environments (Harlow, Schiltz, & Harlow, 1969), in approach to complex stimuli (Sackett, 1972), and in suppression of ongoing response chains (Sackett, 1970). With respect to social activities, adult isolate-reared monkeys typically display excessive and inappropriately directed aggres-

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Total social isolation of macaque monkeys for at least the first 6 months of life consistently produces severe deficits in virtually every aspect of social behavior. Experiments designed to rehabilitate monkeys reared in isolation are described. While young isolates exposed to equal-age normal peers achieved only limited recovery of simple social responses, some mothers reared in isolation eventually exhibited acceptable maternal behavior when forced to accept infant contact over a period of months, but showed no further recovery; isolate infants exposed to surrogates were able to develop crude interactive patterns among themselves. In contrast to the above results, 6-month-old social isolates exposed to 3-month-old normal monkeys achieved essentially complete social recovery for all situations tested. It is postulated that social stimulation that both permits subjects to achieve contact acceptability and provides an interactive medium conducive to gradual development of sophisticated social behaviors will result in almost complete recovery of social capabilities previously obliterated by rearing in isolation.Social isolation has long been identified as a powerful precipitating agent in disruption of normal social development in human beings. While ethical considerations and practical constraints have obviously restricted controlled scientific study of isolation with human subjects, it has been possible to systematically investigate the effects of total social deprivation upon closely related, nonhuman, primate species. The unequivocal finding of numerous researches on macaque monkeys has been that total social isolation for at least the first 6 months of life enormously damages or destroys subsequent social and sexual behavioral capabilities (1-3). Monkeys so reared were grossly incompetent in interactions with socially normal age-mates. As infants and adolescents, they failed to initiate or reciprocate the play and grooming behaviors characteristic of their peers. As adults, these monkeys consistently exhibited abnormal sexual, aggressive, and maternal behaviors.It is clear that early social deprivation is an enormously effective procedure for the production of psychopathological behavior patterns. Less well known is the degree to which social behaviors can be recovered after early social isolation. The data that follow indicate that social deprivation early in life does not necessarily produce irreversible behavioral deficits, and that rehabilitation of varying extent can be effected via judiciously chosen experimental procedures.Several pairs of rhesus monkeys reared for the first 6 months of life in total social isolation chambers (4) were tested on a daily basis in a social playroom (4) with pairs of socially competent age-mates. In comparison to the normal stimulus animals, the isolates were clearly inferior on virtually every behavioral measure throughout the 8-month testing period.1534