A Classic Study of Environmental Influence

Psychologists have long argued about the relative importance of genetics and environment in determining human intelligence—an issue that is sometimes referred to as the "nature vs. nurture" debate.

One reason that this question is hard to resolve is that many obstacles stand in the way of researchers who seek to investigate the effects of early childhood environment. Because the presumed environmental effects occur over a long period of time, it obviously would be impractical to conduct experiments in the laboratory. Moreover, ethical considerations ordinarily keep researchers from manipulating the real-life environment of a child.

In the classic 1966 study by Harold M. Skeels, however, these obstacles were overcome because the researcher was able to find and make use of an "experiment in nature". Skeels' study began by chance during the 1930's when he was serving as a psychologist for the state of Iowa. Among his duties was the psychological testing of young children in an orphanage. One day he examined two baby girls who had been legally committed to the orphanage because their mothers, who were each mentally retarded, had neglected them. The girls were emaciated and pitifully inactive, spending their days rocking and whining. Skeels found that, although there was no evidence of physical defects, the girls showed the mental development of children less than half their ages: the 16-month-old had a level of seven months; the 13-month-old had a level of six months. In those days, psychologists generally regarded intelligence as a genetically determined characteristic that was relatively fixed at birth. The two little girls were given up as unadoptable and, two months later, they were transferred to the Glenwood State school, an institution for the mentally retarded.

Six months after the transfer, Skeels visited the two little girls at Glenwood. He scarcely recognized them. They were alert, smiling, and active. Skeels tested them again and found to his astonishment that they were now approaching normal mental development for their age. Subsequent tests when the girls were about three years of age confirmed their progress.

What could explain the remarkable changes in their behavior and mental development? Skeels concluded that the change in environment had to be responsible. The orphanage where the girls spent their early months was understaffed and overcrowded. Much of the time, the young children were confined to large cribs with very little chance for human interaction. At Glenwood, by contrast, the two little girls had a homelike environment, rich in affection and interesting experiences. They lived in a ward with women ranging in age from 18 to 50 (mental age from 5 to 9) who, in effect, "adopted" them. They also received a lot of affection and attention from attendants and nurses who bought them toys and picture books and took them out for excursions.

All of this gave Skeels the idea for a bold experiment. He convinced the administrators of the orphanage to transfer 10 more children to the Glenwood State School, pointing out that there was nothing to lose as the children all seemed destined for mental retardation in any case. His experimental group consisted of 13 children—the two little girls who had transferred earlier, a third girl who had been transferred at about the same time, and the ten new transfers. All were under three years of age, and all had been certified as retarded. Their IQ scores ranged from 35 to 89 with a mean of 65. The progress of this experimental group at Glenwood was measured against that of a comparison group of 12 children who remained at the orphanage. The comparison group was considerably closer to average intelligence, with a mean IQ of 87.

The contrasts between the two different environments—the drab, sterile orphanage and the lively, stimulating mental institution—became even more marked as the children grew older. At the orphanage, there was little stimulation. Those children over two years old lived in cottages where one matron, aided by three or four untrained girls, had charge of 30 to 35 boys and girls. The cottages were so crowded that the children had to be tightly regimented. At age six, they attended the orphanage elementary school. Later, they were sent to public junior high school where there were few opportunities for individual attention and where they quickly fell behind in their work.

Meanwhile, at Glenwood, the transfers from the orphanage had a much more active and lively life. They were "adopted" by adults—attendants as well as the mentally retarded residents. Each child thus had the opportunity for an intense one-to-one emotional relationship with an older person. The children could often play outdoors on tricycles, swings and other equipment. And at the school at Glenwood, the matron in charge singled out children in need of special attention, allowing them to spend stimulating time each day visiting her office.

After several months, Skeels tested the children in the experimental and comparison groups. The13 children in the enriched environment at Glenwood showed an average gain in IQ of 27.5 points and 3 of the children gained over 45 points. In contrast, the 12 children in the deprived environment at the orphanage showed a decline in average IQ of 26.2 points.

Even more impressive were the results of the follow-up study conducted by Skeels 21 years later. All 13 children in the Glenwood experimental group—11 of whom had been placed for adoption—were self-supporting. In the comparison group, four were still wards of institutions and one had died. The median education level in the experimental group was the twelfth grade, in the comparison group less than the third grade. In the experimental group, subjects held jobs ranging from professional and business occupations to domestic service. Comparison group members who were not institutionalized tended to have low-level jobs.

Skeels' study had one methodological shortcoming: there was no way in which he could completely rule out possible innate differences in his subjects. That is, there may have been some degree to which the 13 children who were transferred to Glenwood had a higher level of intelligence than those who remained behind. Nonetheless, Skeels' study provides extremely persuasive evidence—in the short run and over a period of more than two decades—for early environment as a powerful force in the shaping of intelligence.