This research study was conducted in Trinidad and Tobago to investigate students' responses to a summative assessment of a cross-cultural unit of work. The unit was designed to help students learn Western science by building bridges between their traditional practices and beliefs on selected health-related matters and conventional science concepts. Students' responses to a summative test were analysed qualitatively by a process of coding and categorising. The results indicated, firstly, that students did not necessarily show that they had learned conventional science when personalised tasks were associated with contextualised stimuli. Secondly, students' responses provided evidence of parallel collateral learning. These findings were deliberately explored during a second research cycle. The initial findings were corroborated. In addition, examples of dependent and secured collateral learning emerged. There are implications for assessment policy and for further research to develop a science of science within the Caribbean.