This study used a diffusion chain paradigm to explore the cultural transmission of causally irrelevant tool actions in chains of adult participants. Each chain witnessed an “expert” adult retrieve a reward from inside a puzzle box using a combination of causally relevant actions and causally irrelevant actions. Which of the actions were causally relevant was evident in two of the chains where a transparent box was used. In the other two chains, the causal effectiveness of the tool was hidden inside an opaque version of the box. Results indicated that fewer of the irrelevant actions performed by the expert model were reproduced in the transparent box chains, than the opaque box chains. However, irrelevant actions, although not in their original form, were evident within each chain suggesting that causally irrelevant tool actions can survive within groups of adults. The current article places these results, alongside those from earlier overimitation studies, within a framework of cultural evolution. The proposal here is that the social learning of irrelevant actions is heavily influenced by the interaction between various transmission biases, including frequency-based biases, model-based biases, and content-based biases. It is further proposed that the transmission bias witnessed may differ according to the interplay between characteristics of the model, characteristics of the observer, and the contents of the task. (PsycINFO Database Record (c) 2016 APA, all rights reserved).