Developmental Psychology

Revisiting the Classic Studies

Alan M Slater, Paul C Quinn, Alan M Slater, Paul C Quinn

• Publisher: SAGE Publications Ltd
• Year: 2020
• ISBN:
  9781529737318
• Edition: 2
• Topic: Psychologie
• Subtopic: Entwicklungspsychologie

This book will introduce you tostudies in developmental psychology that changed the way we think about the discipline today. Each chapter provides details of the original work and explains their theoretical and empirical impact, before discussing the ways in which thinking and researchhas advanced in the years since the studies were first conducted. This edition looks at 16 different studies including topics such as the visual cliff, object permanence, and attachment as well as researchers such as Piaget, Vygotsky, and Ainsworth.

1 Attachment and Early Social Deprivation Revisiting Harlow’s Monkey Studies

Roger Kobak

Background to the Classic Study

In his 1958 presidential address to the American Psychological Association, “The Nature of Love,” Harlow suggested that the psychologists, “at least those 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.” Furthermore, he noted that the failure of experimental psychologists to consider love or affection stood in sharp contrast to “the attitude taken by many famous and normal people” (Harlow, 1958). For Harlow, it was an “obvious fact” that the human infant’s affection for the mother provided a basis for later close relationships and the development of subsequent affectional bonds (Harlow & Zimmerman, 1958). By the time “Social Deprivation in Monkeys” was published in Scientific American (Harlow & Harlow, 1962), Harlow’s experiments with rhesus monkeys had clearly established that affectional bonds could be the subject of scientific investigation. This initial work laid the foundation for examining the effects of early social experience on later personality development.

Harlow’s experiments during the 1950s had challenged prevailing learning and psychoanalytic explanations of the infant-mother relationship. Learning theorists viewed the reinforcement that infants associated with feeding as the primary factor accounting for the formation of the mother-infant bond. In this view, the mother-infant relationship was a secondary byproduct of the reduction of the primary drives that included hunger, thirst, and pain. Psychoanalytic models converged with learning theories by focusing on oral needs for nurturance as the primary motivational system during the infant stage of development. Harlow noted that one problem with the learning or drive reduction model was that it failed to account for the lifelong, unrelenting persistence of the bond following extinction trials when the mother ceases to be associated with feeding. Instead he started with the idea that infants were predisposed to forming an affectional bond with the mother, a predisposition that was independent of their need for food.

The “surrogate” mother studies provided a critical test of Harlow’s notion that infant monkeys were motivated by a primary need for affection or “contact comfort.” He had observed that young monkeys became “attached” to soft cloth pads and showed distress when they were separated from them (Harlow & Zimmerman, 1959). The contact comfort derived from the terry cloth was a variable that could be clearly distinguished from feeding as a factor influencing the formation of the infant-mother affectional bond. By creating “surrogate” wire and cloth mothers, the preferences of infants for different surrogates could be measured and variables that were critical to the mother-infant bond could be evaluated. In a series of studies using the surrogate preference paradigm, Harlow demonstrated that infant monkeys showed large and consistent preferences for cloth surrogates that provided contact comfort over wire surrogates that provided food.

Beyond accounting for the factors that led to the formation of the affectional bond, Harlow’s studies also demonstrated the function of the bond in reducing fear and promoting exploratory activity. Harlow set up laboratory situations that not only gave the infant monkey access to the mother surrogate, but also tested how monkeys responded to fear situations such as the “open field test” and exploratory situations evoked by novel objects. In fear situations, infants sought contact with the cloth surrogate, and the contact resulted in comfort and reduced fear. After a period of contact, monkeys were able to use the cloth surrogate as a base for gradually approaching novel stimuli. These exploratory bouts were balanced with contact seeking toward the surrogate, suggesting that monkeys were using the cloth surrogate as a secure base for exploration. The interplay between the attachment, fear, and exploratory systems that Harlow observed in his laboratory monkeys suggested an alternative view of motivation that was consistent with the views of ethologists that motivational systems could be understood as serving biological functions in promoting species survival.

Description of the Classic Study: The Effects of Early Social Deprivation on Later Development

After establishing the significance of the infant-mother bond, Harlow conducted a series of studies on the effects of early social deprivation on subsequent adaptation (Harlow & Harlow, 1962). René Spitz’s studies of children raised in institutions had called attention to potential problems resulting from early maternal deprivation. In the 1940s, Spitz had identified a syndrome which he termed “hospitalism” that suggested institutionalized children were subject to severe depressive symptoms and possible long-term damage to their adult personality (Horst & Veer, 2008). By systematically exposing infant monkeys to varying degrees of social deprivation, Harlow addressed a series of questions about early social experience that had clear implications for the treatment of young children. His prospective designs could not only control exposures to early social adversity, but also map their effects on subsequent adaptation.

The largest sample reported in the 1962 paper consisted of 56 monkeys that had been raised in conditions of “partial social isolation.” These monkeys had been housed in cages where they could see and hear other monkeys but not interact or make physical contact with them during their first year of life. At ages ranging from five to eight years, a period that is equivalent to adulthood in humans, Harlow noted that this group showed a range of abnormalities compared to monkeys who had been born in the wild and brought to the lab as preadolescents or adolescents. Compared to monkeys born in the wild, who were subsequently housed in cages, the laboratory-born monkeys “stare fixedly into space, circle their cages in a repetitive stereotyped manner and rock for long periods of time.” Many of the lab-raised monkeys showed obsessive behaviors such as repetitively picking at skin. In some cases, these obsessive patterns became more extreme or “self-punitive” including behaviors such as chewing or tearing at a body part until it bled. The laboratory-raised monkeys also showed difficulty in interacting with others. At the approach of another person, lab-raised monkeys would show “a complete breakdown and reversal of normal defensive behaviors,” resorting to withdrawn and self-aggressive behaviors.

A series of pilot experiments followed. The first study sought to replicate the initial findings. Six monkeys that had been cage-raised for their first two years, or under conditions of partial social isolation, were compared to six matched monkeys who had been raised in the wild for the first year and subsequently housed in cages during their second year. At two years of age, none of the lab-raised monkeys showed normal sexual behavior with peers. These monkeys displayed sexual approach but did not orient themselves correctly and did not succeed in mating. As these monkeys grew older, they tended to pay less attention to animals in neighboring cages and no heterosexual behavior was observed between male and female cagemates, even between those that had lived together for as long as seven years.

Harlow also compared the cage-raised monkeys to monkeys who were provided with the cloth surrogates that had been used in his early studies. These infant monkeys formed a clear “attachment” to the cloth surrogates and this attachment persisted even following two years of separation from the surrogate. However, as the 60 cloth-surrogate monkeys matured into adolescence and adulthood at three to five years of age, their behavior was as socially and sexually aberrant as that of the monkeys who had been raised under conditions of partial social isolation in bare wire cages. When exposed to adolescent and adult monkeys raised in the breeding colony, not one of the males and only one of the females showed normal mating behavior. By comparison, all of the monkeys born in the wild and captured during their first year, and then housed together in captivity, displayed normal sexual behavior. They had learned to live with others in a stable hierarchy of dominance, fought less, and engaged in social grooming.

Another study tested the extent to which early social deprivation could be reversed by later experience. Harlow moved 19 lab-raised monkeys to the municipal zoo where they had to contend with new survival challenges more in line with those experienced by monkeys living in the wild. In this new environment, the lab-raised monkeys had to drink from a trough, compete for food, and learn to live together in a group. Although three of the monkeys died or showed severe stress in making the transition, the remaining monkeys were able to establish a dominance hierarchy that reduced fighting, formed friendship pairs, and displayed some sexual behavior. However, the sexual behavior was infantile in form and did not result in any females becoming pregnant. When returned to the laboratory, the monkeys ceased to groom and returned to more frequent fighting and aggressive behavior. Harlow viewed this attempt at rehabilitation largely as a failure.

Yet another set of studies tested the differential effects of both the duration and degree of early social isolation on later outcomes. Monkeys were exposed to total social isolation, a condition in which they we...