There is extensive evidence that adults, children, and some non-human species, represent routine events in the form of hierarchically structured 'action scripts,' and show superior recall and imitation of information at relatively high-levels of this hierarchy. Here we investigate the hypothesis that a 'hierarchical bias' operates in human cultural transmission, acting to impose a hierarchical structure onto descriptions of everyday events, and to increasingly describe those events in terms of higher hierarchical levels. Descriptions of three everyday events (going to a restaurant, getting up and going shopping) expressed entirely in terms of basic low-level actions were transmitted along ten chains each containing four adult human participants. It was found that the proportion of low-level information showed a significant linear decrease with transmission generation, while the proportions of medium- and high-level information showed significant linear increases, consistent with the operation of a hierarchical bias. The findings additionally provide support for script theory in general, and are discussed in relation to hierarchical imitation in non-human primates.