What is the primary determinant of intelligence? Is it heredity? Is it environment?
Or, is it possible that the best answer can’t be given in either-or terms?
The topic under discussion in this section is sometimes called the nature- nurture controversy, and it has a long history in philosophy, biology, and psy- chology. Nature refers to heredity; the primary characteristic of nature, or heredity, is the potentialto reach a given level of intelligence. Nurture,on the other hand, refers to environment; the primary characteristic of nurture, or envi- ronment, is its capacity to bring forth, in the case of intelligence, the maximum cognitive potential that an individual has. Or, conversely, environment has the capacity to inhibit and restrict that potential.
(a) The word refers to heredity.
(b) The primary characteristic of heredity is the to reach a given level of intel- ligence.
(c) The word refers to the environment.
Answers: (a)nature;(b) potential; (c) nurture.
Let’s say that a mother and a father insist that their two sons have had the
“same” environment. Both were loved, ate the same kind of food, and received the same kind of cognitive stimulation. Now thirty-year-old Kendrick has a Ph.D. in physics. His brother, twenty-seven-year-old Mark, is an insurance bro- ker. The parents say that since early childhood Kendrick has had a brilliant, unusual mind. Mark has always appeared to have normal intelligence. The par- ents are convinced that the difference in the cognitive functioning of their two sons is intrinsic, something that is built in to the two individuals. This general line of reasoning tends to support the importance of heredity. It can be argued that the individual differences in the two brothers have a genetic basis. Although siblings do have many genes in common, there is still plenty of room for unique genetic patterns.
A strong advocate of the importance of environment in shaping intelligence is likely to point out that, strictly speaking, the two brothers didn’t have the same environment. That is why the word same appeared with quotes around it in the above paragraph. It is possible to suggest, as the pioneer psychotherapist Alfred Adler did, that a first child and a second child have, by definition, different envi- ronments. The first child lives for a time as an only child. The second child always lives in a world with a sibling. It is possible to hypothesize that a first child often receives, for a time, more attention and affection than a second child is likely to receive.
In spite of the Adlerian birth-order argument, when individuals are raised in the same home and with the same parents, variations in intelligence tend to sup- port the genetic hypothesis.
(a) Individual differences in intelligence in siblings who have had highly similar environ- ments are likely to have what kind of a basis?
(b) According to Adler, a first child and a second child have, by definition, envi- ronments.
Answers: (a) A genetic basis; (b) different.
The fictional tale Tarzan of the Apesis a reflection of the genetic hypothesis.
Tarzan, after all, develops the intelligence of a human being even though he’s raised in an environment of ape intelligence. However, as indicated, Tarzan is a
fictional character. Children raised by animals or in deprived circumstances are called feral children.When such children are discovered, they seldom display adequate cognitive functioning. A famous case is that of the wild boy of the for- est of Aveyron in France. Discovered at the age of seven and studied by the nineteenth-century physician Jean-Marc-Gaspard Itard, the boy, given the name Victor, never did attain normal intelligence. Similar studies of feral children support Itard’s research findings. So, in spite of the story of Tarzan, it appears that early experiences have to be within the context of a human social environ- ment in order to bring out the individual’s genetic potentiality.
A substantial body of research suggests that a stimulus-rich environment will make a large difference in measurable intelligence. A stimulus-rich environ- ment, for human beings, is one that provides a great deal of affection along with mental stimulation of a verbal and symbolical nature. A child who is played with spontaneously, exposed to the printed word, provided with challenging toys, and encouraged to express himself or herself is likely to automatically maximize his or her genetic potentiality.
(a) The fictional tale of Tarzan of the Apesreflects what hypothesis as an explanation of intelligence?
(b) Children raised by animals or in deprived circumstances are called chil- dren.
(c) A environment, for human beings, is one that provides a great deal of affection along with mental stimulation of a verbal and symbolical nature.
Answers: (a) The genetic hypothesis; (b) feral; (c) stimulus-rich.
We can see that in a best-case scenario the function of the environmental fac- tor is to elicit, or bring forth, the genetic potential of the child. It can’t put that potential there, but it can help make it reach its highest and best level.
The concept of an interaction, a formal mathematical concept, is useful at this point. An interactionoccurs when two (or more) variables affect each other in a complex way. In contrast, the relationship between two variables is said to be addi- tive when they don’t affect each other’s value. For example, 3 ×3 =9. The rela- tionship between the numbers is interactive because the whole (the product) is more than the sum of its parts. On the other hand, 3 +3 =6. In this case the rela- tionship between the numbers is additive because the whole (the sum) isthe sum of its parts.
Loosely speaking, a kind of “magic” occurs when there is an interaction.
Something is produced that is not “in” the original variables. So it is with intelli- gence. It is very difficult to say, when there is an interaction, that one factor is of greater importance than another factor. It is the joint effects of the two factors working together that produce a result. In the case of intelligence, the nature-
nurture controversy is something of a false issue. The correct formula for under- standing intelligence is this one:
Heredity ¥Environment = Intelligence
(The multiplication sign is used to symbolize an interaction.)
The answer to the heredity-environment debate should not be given in either-or terms. The answer should be given in both-andterms. Both heredity and environment, interacting, play important roles in determining intelligence.
(a) An occurs when two (or more) variables affect each other in a complex way.
(b) What is the correct formula for understanding intelligence?
Answers: (a) interaction; (b) Heredity ×Environment=Intelligence.
SELF-TEST
1. One of the following is nota primary characteristic of intelligence:
a. The ability to think clearly b. Eccentric thinking
c. Convergent thinking
d. Functioning effectively in the environment 2. In behavioral science, intelligence has the status of
a. a hypothetical construct b. a psychological atom
c. a transcendental force d. an interim operant
3. What method was employed by Binet and Simon to measure intelligence?
a. The biometric method
b. The perceptual-motor method c. The performance method d. The physiological method
4. A research project that measures behavior over a span of time is called a a. discontinuity study
b. gradient study c. longitudinal study d. continuity study
5. Which of the following is the correct formula for the intelligence quotient (IQ)?
a. IQ =MA×CA+100 b. IQ =CA+MA×3.14
c. IQ =MA+MA/100 d. IQ =MA/CA×100
6. An IQ score in the range 110 to 119 is associated with what classification?
a. Very Superior b. Superior
c. Bright Normal d. Normal (or Average)
7. A test that measures what it is supposed to measure is said to be a. consistent
b. reliable c. valid d. congruent
8. A test that gives stable, repeatable results is said to be a. authentic
b. reliable c. valid d. systematic
9. The inborn potential to reach a given level of intelligence is associated prima- rily with which of the following?
a. Nature b. Nurture
c. Environment d. Reinforcement
10. The correct formula for understanding intelligence is which of the following?
a. Heredity ×Environment=Intelligence b. Heredity +Environment=Intelligence
c. Nature ×Heredity=Intelligence d. Nurture ×Environment=Intelligence
ANSWERS TO THE SELF-TEST
1-b 2-a 3-c 4-c 5-d 6-c 7-c 8-b 9-a 10-a
ANSWERS TO THE TRUE-OR-FALSE PREVIEW QUIZ
1. True.
2. True.
3. False. There is an information subtest in the Wechsler Intelligence Scales.
4. False. An intelligence quotient (IQ) score of 100 is associated with normal, or average, intelligence.
5. True.
KEY TERMS
bell-shaped curve (normal curve, or Gaussian curve)
Binet-Simon Scale biometric method
chronological age (or CA) convergent thinking correlation coefficient environment
face validity factor analysis feral children general factor (or g) hypothetical construct intelligence
intelligence quotient (or IQ) interaction
kinesthetic intelligence longitudinal study mental age (or MA) multiple intelligences
nature
nature-nurture controversy nurture
outside criterion
performance intelligence performance method potential
reliable test social environment
specific mental abilities (or s)
Stanford-Binet Intelligence Scale (SBIS) stimulus-rich environment
valid test
verbal intelligence
Wechsler Adult Intelligence Scale (WAIS) Wechsler Intelligence Scale for Children (WISC)
Wechsler Preschool and Primary Scale of Intelligence (WPPSI)
Wechsler Scales