I wonder what the research shows for different age groups, and if the results vary, regarding synapse development. I wonder how long synapse development continues!From How People Learn, here's some background on those issues.
There are two different patterns to how we develop synaptic connections.
In one process, "synapses are overproduced and then selectively lost." That process is especially in early development, and the time it takes varies depending on the part of the brain, " from 2 to 3 years in the human visual cortex to 8 to 10 years in some parts of the frontal cortex."
The other process lasts all the way through life, and involves adding new synapses as one adds experiences.
Noting the two different processes seems to fit the simultaneous ideas that the early years especially important and yet learning is a lifelong process.