In this talk I review studies by my own group and by others that grapple with two topics that I suggest should be linked: over-imitation and conformity. These have developed separate research literatures that hardly refer to each other, but I propose that they should, because in both of them social learning from others over-rides personal information, a powerful cultural phenomenon. In over-imitation, that we first identified a decade ago, a child faithfully copies even those acts of another that appear manifestly ineffectual. A minor research industry on the topic has since developed, identifying over-imitation across a growing number of cultures and surprisingly diverse age ranges. Conformity in its most intense form involves abandoning personal preferences in favour of the alternatives information of behaviours of a majority of others, but is manifested in other ways too. Whereas there is evidence suggesting that over-imitation is special to humans, conformity may be more widespread among species. I review examples from both developmental and comparative studies to construct conceptual schemes in which the nature and scope of both over-imitation and conformity can be situated.