Final answer:
The auditory and visual cortexes in the brain experience the fastest development during infancy, a period characterized by significant brain growth, with adolescence following as a period of increased cognitive complexity and efficiency.
Step-by-step explanation:
The auditory and visual cortexes in the brain develop rapidly during infancy. This is the period when the brain undergoes significant growth in size, with about 90 percent of its adult size achieved by the age of six. While the overall increase in brain size slows down beyond this point, the cognitive development and complexity significantly increase during adolescence.
During adolescence, there is substantial development in brain structure and function. The cerebral cortex becomes more intricate with an increase in the number of folds, and processes like synaptic pruning and myelination enhance the brain's efficiency. Although the brain's growth in size stabilizes, cognitive abilities such as attention, memory, processing speed, and organization develop to levels comparable to adults. Moreover, cognitive development continues into early adulthood, as seen with the frontal lobes reaching full maturity by the age of 25, contributing to enhanced insight and judgment.
It is also during adolescence that individuals become more aware of aspects such as their sexual orientation. The transition to adulthood brings about new cognitive challenges and growth. Cognitive development does not stop with adolescence; it continues throughout adulthood, with ongoing changes into old age. Therefore, the correct answer is A. Infancy, as this is when the size and basic structure of the auditory and visual cortexes have their most significant growth spurt.