ADAPTIVE NATURE OF COGNITIVE IMMATURITY

The major theme of this chapter is that human infants and children have been prepared

by

evolution to acquire some types of information more readily than others-that there are enabling constraints that make the process of learning certain classes of information easier than others. Consis- tent with this contention is the idea that some information will be most easily acquired at particular times in ontogeny. This is related to the concept of critical, or sensitive, periods.

A

related hypothesis is that some aspects of developmental immaturity, rather than simply being limitations that the child must overcome on the way to adulthood, make certain forms of cognitive development easier, much as a limited working-memory capacity is proposed to be related to greater ease of language acquisition.

We discussed in chapter

2

the potential adaptive role of immaturity in development (Bjorklund,

1997b;

Bjorklund & Green, 1992; Wellman, in press). In that chapter, we provided specific examples relating to children’s play and neonatal imitation. In this section, we discuss theory and research

suggesting that certain aspects of children’s immature cognitions are actually adaptations that facilitate overall cognitive development.

Species-Atypical Experience and Subsequent Development

Developmental psychobiologists Gerald Turkewitz and Patricia Kenny

(1982)

proposed that the immaturity of sensory and motor systems may play an adaptive role early in development. The limited motor capacities of altricial animals (those that are physically immature and helpless at birth and need substantial parental care) prevent them from wandering far from the mother, thus enhancing their chances of survival.

Of

greater interest, however, was their proposal that sensory limitations of many young animals are adaptive in that they reduce the amount of information infants have to deal with, which facilitates their constructing a simplified and comprehen- sible world.

In chapter

2,

we presented research demonstrating how varying the prenatal environment of precocial birds can alter species-typical behavior (Gottlieb, 1976). Related to this is research showing how presenting animals with “experiences” outside of the species-typical range early in ontogeny can disrupt development. For example, Lickliter

(1990)

removed part of the eggshell of bobwhite quails two to three days before hatching and provided visual experience (patterned light) to these animals.

Of

course, quail chicks would not normally see patterned light until after hatching.

Following hatching, the quail chicks were placed in a circular tub, with the maternal call of a quail coming from a speaker on one side of the tub and that of a chicken coming from a speaker on the opposite side. The findings from this study are shown in Figure

6.3.

A group of control animals that had the eggshell removed but

did

not receive any additional visual experience displayed the species-typical pattern, approaching the maternal call of their own species on most occasions. In contrast, most of the animals exposed to light showed no preference or approached the maternal call of a chicken.

It is worth noting that these animals

did

show enhanced visual discrimination abilities relative to control animals (a facilitory effect of early, species- atypical experience), but at a cost to auditory discrimination abilities. Other research, using ducks, quails, and rats as subjects, has demonstrated that providing young animals with stimulation that is outside the species norm has negative consequences for development (Gottlieb, Tomlinson, & Radell,

1989;

Kenny & Turkewitz,

1986;

Lickliter & Hellewell,

1992;

Lickliter &

Lewkowitz,l995; McBride & Lickliter, 1994; Spear,

1984).

Neonatologist Heidelise Als ( 1995) has suggested that premature

hu-

man infants have experiences similar in nature to those of Lickliter’s bob- white quails. Als suggested that the stimulation that premature infants often receive in hospitals disrupts brain development (particularly of the frontal 186 THE ORIGINS OF HUMAN NATURE

Figure 6.3. Percentage of bobwhite quail chicks that approached the bobwhite maternal call, the chicken maternal call, or showed no preference as a function of whether they received premature visual stimulation.

Note. Adapted from “Premature Visual Stimulation Accelerates lntersensory Functioning in Bobwhite Quail Neonates,” by R. Lickliter, 1990, Developmental Psychobiology, 23, pp. 15-27. Copyright 1990 by Wiley. Adapted with permission.

cortex) during sensitive periods, frequently causing impairments resulting in speech problems, eye-hand coordination difficulties, impulsivity, attention deficits, and lowered

IQ.

However, these deficits are often accompanied

by

accelerated development or enhanced abilities in other areas, such as mathematics. Als interpreted these findings in premature infants much as Lickliter did for bobwhite quail. Stimulation outside the species-typical range can have unforeseen consequences on brain and behavior development. Als

(1995)

wrote,

Social contexts evolved in the course of human phylogeny are surpris- ingly fine-tuned in specificity to provide good-enough environments for the human cortex to unfold, initially intrauterinely, then extrauterinely

. . .

With the advances in medical technology, that is, material culture, even very immature nervous systems exist and develop outside the womb. However, the social contexts of traditional special care nurseries bring with them less than adequate support for immature nervous systems

. . .

leading to maladaptations and disabilities, yet also to accelerations and extraordinary abilities. (p. 462)

The findings presented above indicate that extra prenatal stimulation in one sensory system can affect adversely later learning in another system.

Related to this issue is the question of whether an early learning experience in infancy can interfere with later learning.

Several studies have found that rats who began conditioning early in life actually produced lower levels of eventual learning, compared to rats who began training at a later age (Rudy, Vogt, & Hyson, 1984; Spear &

Hyatt, 1993). Similar evidence of a detrimental effect of early learning on later learning was provided

by

comparative psychologist Harry Harlow ( 1959), who was studying object-discrimination learning in rhesus monkeys.

Monkeys who began discrimination training at

155

days of age or younger actually performed more poorly on the learning tasks later in life than animals who did not begin training until 190 days of age or older. This was true despite the fact that the “early” animals had more experience on the task than the older animals. Performance on these problems, beginning at age

120

days, is shown in Figure

6.4

as a function of the age at which monkeys began training. Harlow

(1959)

concluded that

there is a tendency to think of learning or training as intrinsically good and necessarily valuable to the organism. It is entirely possible, however, that training can either be helpful or harmful, depending upon the nature of the training and the organism’s stage of development. (p. 472)

“Readiness” and Early Education

Formal education is a novelty for Homo supiens, a cultural invention only thousands of years old at most, and only in the past century has a majority of humanity received even moderate levels of schooling. Yet, within some cultures, children begin formal education during the preschool years.

Moreover, some of the discoveries relating to infant and fetus learning have resulted in movements to push formal education back to the crib and, in some cases, to the womb (Doman,

1984).

The evolutionary developmental perspective taken here, however, suggests that imposing formal education on children before they are biologically “ready” or “prepared” to learn will have few positive consequences and may have some negative effects. Surpris- ingly, there has been little systematic research on this socially important issue. There are a few notable exceptions, however.

In

one study, researchers Marion Hyson, Kathryn Hirsh-Pasek, and Leslie Rescorla (

1990;

Rescorla, Hyson, & Hirsh-Pasek, 1991) compared the effects of early high-academic versus low-academic preschool programs on middle-class children’s school-related behavior in kindergarten. Children 188 THE ORlGlNS OF HUMAN NATURE

90

80

70

60

I

P

I I

-

-

-

-

I I I I I I

~~ ~~

dU

85 120 155 190 225 260 295 330 365 400 Age at Testing (days)

Figure 6.4. Discrimination learning set performance of rhesus monkeys as a function of age at which testing was begun.

Note. From “The Development of Learning in the Rhesus Monkey,” by H. Harlow, 1959, American Scientist, December, pp. 459-479. Copyright 1959 by American Scientist. Reprinted with permission.

were given tests of academic skills, social competence, emotional well-being, and creativity at the end of their prekindergarten program and again toward the end of kindergarten. High-academic prekindergarten programs stressed adult-directed instruction, whereas low-academic programs did not but in- stead followed a “developmentally appropriate” curriculum (Bredekamp &

Copple,

1997).

There were no significant differences in academic ability either at the end of prekindergarten or kindergarten between the children who attended the high-academic and low-academic programs. A small differ- ence was found for test anxiety at the end of preschool, with children attending the academically oriented schools showing greater test anxiety than children attending the developmentally appropriate programs. Correla-

tional analyses revealed that mothers who scored high on an adult-instruc- tion scale tended to have children rated as lower in creativity. (Mothers’

belief in adult-instruction positively predicted children’s performance on an academic skills test in preschool, but this relation disappeared in kinder- garten.) Also, the greater the emphasis a preschool placed on adult-directed practices, the higher children’s school-related anxiety. Finally, children who attended the developmentally appropriate schools were more likely to have a positive attitude toward school than were children who attended the high- academic programs.

Hyson and her associates cautioned that most of these effects, although statistically significant, were small in magnitude. Nevertheless, in general, there were no long-term benefits of an academically oriented preschool program and some evidence that such programs might have negative conse- quences (e.g., greater stress). Based on these findings, Hyson and colleagues concluded that there seems to be no defensible reason for encouraging formal academic instruction during the preschool years. Rather, for most children from middle-class homes, cognitive development and creativity can best be fostered in a developmentally appropriate preschool program that considers children’s limitations as well as their abilities.

In

the opinion of these researchers, “it may be developmentally prudent to let children explore the world at their own pace rather than to impose our adult timeta- bles and anxieties on them” (Hyson et al., 1990, p.

421).

Although the results of this and related (Weikart & Schweinhart,

1991)

studies must be viewed cautiously, they are consistent with the per- spective that cognitive development during the early years of life is best accomplished outside a formal, teacher-directed environment. Young chil- dren’s cognitive system is immature, and because of this, learning and devel- opment might take place best in unstructured settings. The skills of young children are different from the skills of older children and might be ideally suited for the learning they need to do at this time in their lives (Bjorklund,

199713;

Bjorklund & Green,

1992).

These findings argue that children ought not be hurried through a childhood that has purposes in and of itself.