This six-month-old baby discovers movements that prepare him for further development and lead to his ability to walk later on.

Early Deprivation

1. Infant monkeys were reared in total darkness from birth to three months, except for a brief period each day when they were exposed to light while wearing special goggles that permitted only diffuse, unpatented light to reach the eyes. When the monkeys were first exposed to light without goggles, they showed serious deficiencies in visual-motor behavior. They could not track moving objects with their eyes, did not blink when threatened by a blow to the face, not put out their arms when moved rapidly toward a wall.

However, these skills improved with continued visual exposure, and by the end of several weeks the dark-reared monkeys were performing as well as normal monkeys. In most instances they acquired the responses in less time than had the normal monkeys at an earlier age.

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This study provides evidence for the importance of both maturation and experience. Fully adequate use of vision depends on neuromuscular growth continuing after birth as well as on practice in the use of vision. The dark-reared monkeys required experience in light before they could develop the proper response; but the fact that they required much less experience than newborn monkeys once the goggles were removed is evidence of the role of maturation (Riesen, 1965).

2. In another experiment, dogs reared in confined quarters were perfectly healthy but in some respects appeared “stupid” (Scott, 1968). For example, they seemed insensitive to pain. They did not respond to a pin prick or to having their tail stepped on. Time after time, they would investigate a lighted match by putting their nose into the flame. Whatever the felt experience may have been, certainly the pain stimulus did not evoke the avoidance responses found in normal dogs. Subsequent studies with other species have led to the conclusion that restriction or deprivation of simulation generally produces animals that in later life do not learn new tasks as quickly as their normal counterparts.

Enriched Environments

1. What will be the psychological effects if we provide an organism with an unusual amount of stimulation instead of a restricted or deprived environment? Young gerbils (small mouse­like rodents) housed together in a large cage equipped with various kinds of toys differ significantly after thirty days from gerbils kept singly in small, bare cages. They perform better on learning tasks; their brains weigh more and show a higher concentration of some of the chemicals associated with learning.

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2. Human infants may also benefit from an enriched environment, even in the first weeks after birth. One study showed the effect of early stimulation upon visually directed reaching-a visual-motor response that develops in clearly specified maturational steps (White, 1971).

A month-old baby lying on his back will stare at an attractive object held above him but will make no attempt to reach for it. By two months he will swipe at it accurately but with a closed fist. By four months he will alternate glances between his raised open hand and the object, gradually narrowing the gap. By five months he will accurately reach and successfully grasp the object.

3. Although the universality of this response sequence indicates a large degree of maturational dependence, the rate of development can be accelerated. The environment of a group of month-old infants in a state hospital was enriched by

(a) Increasing the amount of handling.

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(b) Placing the infants on their stomachs with the crib liners removed for several periods each day so they could observe the activities around them,

(c) Replacing white crib sheets and liners with patterned ones,

(d) Hanging an elaborate ornament over the cribs featuring contrasting colours and forms to look at and explore with the hands.

Infants receiving this kind of treatment succeeded in visually directed reaching at an average age of three and a half months an contrasted with five months for a control group reared in the relatively unstimulating conditions of normal hospital routine. Interestingly enough, the enriched-environment infants were delayed in one aspect of their development; they did not begin visually studying their hands until around two months, as contrasted with a month and a half for the control infants. With virtually nothing else to look at, the control group discovered their hands earlier than the experimental group.

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4. Note, however, that increased stimulation will not result in accelerated development unless the infant is maturation ally ready. In fact, too much stimulation too soon may be upsetting. During the first five weeks of the above experiment, infants in the enriched group spent less time looking at their surrounding (seeming to ignore the ornament and patterned bumpers) and engaged in much more crying than did the control infants.

It may be that a month-old infant is actually distressed by being surrounded by more stimulation than he is able to respond to. A subsequent study found that providing infants with only a simple but colourful object mounted on the crib rails for the first two months of life and then introducing more complex ornaments during the third month seemed to produce optimal development.

These infants showed no signs of unusual distress, were consistently attentive to their surroundings, and achieved visually directed reaching at less than three months. Thus we see the importance of providing simulation appropriate to the level of maturation (White, 1971).