Testosterone's Effect on Memory

Like many other areas of development, memory generally matures more rapidly in girls than boys. Beginning in the womb, female fetuses are known to habituate to auditory stimuli about two weeks earlier than males. After birth, they are more advanced at visual habituation. Toward the end of the first year, girls are about a month ahead in tests of short-term, explicit memory, like remembering, after a few seconds' distraction, where they just saw a toy being hidden. Girls also outperform boys on a test of long-term implicit memory, the "concurrent discrimination" task... in which they must learn, over many repetitions and for several pairs of objects, which of the pair conceals a tasty Froot Loop. Between one and three years of age, girls make fewer errors on this task than boys; after that. both sexes perform comparably. Finally, females tend to perform better on tests of verbal recall, like remembering details about recent events, a difference that emerges in the fourth year and persists into adulthood.

Studies of infant monkeys have provided some clues to the neural basis for these gender differences. Once again, testosterone appears to be the culprit. Testosterone levels surge in male monkeys early in gestation and remain elevated until three or four months after birth. By six months of age, they are back down to around female levels. (They then surge again at puberty.) Males' performance on the concurrent discrimination task parallels these changes in testosterone, since it is notably poorer than females' at three months but equivalent by six months of age. Even among different three-month-old males, those monkeys with the highest testosterone levels show the poorest memory performance and vice versa. But the most convincing evidence that testosterone influences the development of memory-storage mechanisms in the brain comes from experiments in which hormone levels were manipulated, either by castrating young male monkeys or by injecting testosterone into young females whose ovaries were removed. As predicted, the castrated males remembered which objects were paired with the reward (in this case, a banana pellet) better than normal males and comparably with females of the same age, while the females injected with testosterone performed more poorly than control females.

The testosterone surge in humans lasts somewhat longer than in monkeys, not reaching its nadir until the end of the first year, which may explain why boys are generally slower learners than girls during infancy and early childhood. Testosterone appears to slow cellular development in certain cortical regions, including the inferior temporal cortex, an area of the visual system known to be involved in the concurrent discrimination task and which is both Structurally and functionally more mature in female infant monkeys than in males.

Notes:

Memory develops faster in females and testosterone appears to be the culprit.

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 What's Going on in There? : How the Brain and Mind Develop in the First Five Years of Life
Books, Brochures, and Chapters>Book:  Eliot , Lise (2000-10-03), What's Going on in There? : How the Brain and Mind Develop in the First Five Years of Life, Bantam, Retrieved on 2011-07-18
Folksonomies: parenting babies development infants physiology