What is human intelligence.It is difficult to define. It is the abstract concept used to explain the observation that individuals vary in the skill and effectiveness with which they employ their mental faculties. Intelligence is more easily defined in practice by pointing to instances of its action. This way is in fact used in our daily life. We judge a man’s intelligence by observing his bearing, his speech, his apparent grasp of situations, his judgments, and his emotional control.
Then in the light of our past experience of watching Other men, we call an individual bright or dull. We are doing nothing conceptually different when we.estimate intelligence at the bedside or by means of psychologic tests. We organize the testing so that a series of observations can be made within a reasonable period of time. We add scope to our examination by asking for performance in several different kinds of mental activity. We bring accuracy to the observations by scoring the performance.
The quantitative measurement of the mental attribute of human intelligence, was first attempted by Binet at the turn of the century. His success and the Stanford-Binet battery of tests developed from his work brought such predictive power to the study of intelligence that they provide an impetus to the development of tests to examine other mental functions. But the tests of intelligence have through their revisions, particularly the: Wechsler Bellevue Intelligence Scale published in 1939 and the Wechsler Adult Intelligence Scale (WA1S) of 1955, remained the most secure and useful tests of mental function.
What Is The Nature of Human Intelligence In Psychology
The questions on orientation, memory, attention and concentration, fund of knowledge, and capacity to reason abstractly that constitute the tests of cognition routinely carried out at the bedside in the course of the physical and mental examination of a patient provide a doctor an estimate of his patient’s intellectual functioning. In the light of knowledge of the patient’s past life and demonstrated abilities, the doctor makes a judgment whether there has been damage to intellectual functioning. Psychologic testing should be able to give a more accurate estimate of the intelligence of a patient at the moment of testing than do these bedside examinations if the tests available are reliable and valid. The considerable experience of this century has provided such evidence.
The Wechsler Adult Intelligence Scale IQ Test
The Wechsler Adult Intelligence Scale is the most reliable and valid test we have at the moment for measuring the intellectual function of the adult. Its reliability has been demonstrated by the close correlation of test scores given on separate occasions to the same individuals and by the similarity of scores when one half of a test is compared with another half (split-half method). Its validity has been demonstrated by its correlation with life performances of individuals it scores as intelligent or dull.
In its present form the WAIS consists of 11 sub- tests of mental skill. Six of these subtests are “verbal tests.” In these the patient is requested to define words, to recognize similarities between words, to do arithmetic, to remember numbers forward and backward, to answer questions
on his fund of knowledge, and to judge and interpret proverbs. These tests are followed by five “performance tests,” in which a patient is asked to work with rather unfamiliar material and solve problems set to him by that material.
Tests here include the putting together Of puzzles, work with Symbols, the setting out of logical stories from pictures disorganized for the test, construction of patterns from multicolored blocks, „ and the recognition of things missing from drawings performance tests seem somewhat less related to the education of a person than are the verbal tests. All the subtests that have been chosen for the WAIS have a long history of investigation. They are combined together to produce a thorough and accurate instrument.
The scoring of the WAIS is in the form of the Intelligence Quotient (I.Q.). In fact, the WAIS derives a verbal I.Q. from the verbal tests and a performance I.Q. from the performance tests. A full-scale I.Q. is derived from the combination of all 11 subtests.
The I.Q. compares an individual with others. Historically it was developed for children. I.Q. then was the ratio of mental age over chronological age times 100 when mental age was defined in terms of a child’s ability to succeed on tests which, the average child of a given age could do. Thus-a child solving problems which the average nine- year-old could solve had a mental age of nine. If he, himself, was nine years old at the time of the test, he had an average ability and an I.Q. of 9/9 x 100, or 100; if his chronologic age was six, he would be an advanced child with an I.Q. of 9/g x 100, or 150. Terman demonstrated the constancy of I.Q. in the growing child.
But a ratio of mental to chronological age is unlikely to be useful in adults because tested intelligence does not increase after the late teens. The WAIS and many other tests for adult intelligence continue to use the term I.Q. This is possible because of the fact that tests of intelligence appear to distribute individuals in a gaussian fashion. This curve has a mean at I.Q. 100 and a standard deviation of ± 15 I.Q. points. It is possible to divide the curve into percentiles of the population. The WAIS score of any person places him in the percentile of the population with similar scores, and his I.Q. can be extrapolated from percentile by means of the distribution curve. Thus an individual whose performance on the WAIS is equal to 50 per cent of the population is said to have an I.Q. of 100, whereas individuals whose test performances exceeded 98 per cent of the population will be said to have an I.Q. of 135 or above.
The WAIS has found its greatest clinical utility in the study of patients with brain disease. Any damage to the cerebral hemispheres will injure intellectual ability and disturb the scores on the WAIS. An intriguing observation is that early in the course of brain disease performance tests are disturbed before the verbal tests scores change. This may indicate that? verbal tests measure more what an individual has learned and practiced, whereas performance tests measure his capacity to meet new problems. Intelligence is required for success in both. The verbal and performance scores of normal individuals are usually comparable. The discrepancy between verbal and performance scores found with brain disease reflects a resistance of the verbal tasks to injury.
The Verbal I.Q.For Human Intelligence
The verbal I.Q. can be considered a fair estimate of the original intellectual endowment of an individual suffering from a brain injury. The decline of the performance I.Q. is a useful measure of the degree of injury to the cerebral tissue the patient has endured. With an advancing brain disease verbal I.Q. will fall eventually, but a patient will usually continue to demonstrate higher verbal than performance scores.
Emotional unrest such as anxiety or depression will also interfere with WAIS scores. Here, as’-with cerebral disease, the performance I.Q. will fall below the verbal I.Q., demonstrating that the capacity to work with unfamiliar material is disturbed more than tests of what has been well learned. But because these findings are identical to those in persons with brain disease, the differentiation of an emotional disturbance from dementia cannot come from WAIS results. It must rest on other information such as is derived from the history, physical examination, and mental status.
The WAIS is useful not only in demonstrating deterioration of intellectual function but also when done serially can document recovery of function with treatment. Since it is so simple to employ, its increasing utility in clinical research is assured.
