Until the early 1990s, the scientific consensus was that the adult brain stopped learning and had no plasticity after the age of 25.

The finding

What the evidence shows

There was a real shift in thinking here, but the date and the age are both off. A standard neuroscience textbook places the old assumption, that major rewiring of the cortex happens mainly in early development, as holding until the late 1970s, and Kaas and Merzenich showed adult monkey cortex reorganizing in the early 1980s, not the early 1990s. No scientific consensus ever set a cutoff at age 25. That figure comes from a separate idea about when the frontal lobes finish maturing, which is not the same as the brain no longer learning.