In the initial study, the researchers provided each of two groups of wild monkeys with a box of maize corn dyed pink and another dyed blue. The blue corn was made to taste repulsive and the monkeys soon learned to eat only pink corn. Two other groups were trained in this way to eat only blue corn.  A new generation of infants were later offered both colours of food — neither tasting badly — and the adult monkeys present appeared to remember which colour they had previously preferred. Almost every infant copied the rest of the group, eating only the one preferred colour of corn.  The crucial discovery came when males began to migrate between groups during the mating season.

The researchers found that of the ten males who moved to groups eating a different coloured corn to the one they were used to, all but one switched to the new local norm immediately.

via ‘When in Rome’: Monkeys found to conform to social norms.