Individuals alter what they have learned socially through their own trial and reasoning before passing it on, which gives cultural change a direction that copying alone would not.
Boyd and Richerson distinguished guided variation from biased transmission: here the individual does not choose between models but modifies the one received. Each generation's small adjustments accumulate in a consistent direction, which is why traditions can adapt to local conditions much faster than selection between variants would allow, and why they can also drift steadily toward whatever individual learning finds congenial.
In practice
- A process handed to a new team comes back a year later adapted to their constraints and incompatible with the original.
- A recipe learned from a parent and adjusted for one oven becomes, after three households, a different dish.