constancy of the IQ
a tendency for IQ results to remain approximately the same when the same or a similar test is administered. IQ tends, on average, to remain remarkably constant throughout life, starting after infancy and lasting until old age, when there are often declines (starting roughly 10 years before death). Measures of intelligence in infancy, such as of preference for novelty and of recognition memory, suggest that even infant intelligence may predict intelligence in later childhood and adulthood. However, radical changes in environment can result in radical changes in IQ, as when children are adopted out of orphanages or families in which they have experienced severe privation. Usually, such adoptions produce larger changes in IQ if they occur earlier (e.g., by age 2) rather than later.