Background: The free list, also written "freelist", or "free recall", is an ethnographic method that characterizes the local knowledge of a population about a given cultural domain. However, there is still much to elucidate about the variables that can influence the number of items that participants cite using this technique. This study applied a casual-comparative experimental design to analyze whether 3 months' time, age, and external stimuli influence the similarity of plant free lists applied at different times.
Methods: Data was collected from 103 farmers from the rural community Alto dos Canutos, in the municipality of Picos, Piauí state, Brazil. Two free lists were conducted at two different times, with an interval of three months between them. Subsequently, the similarity between the first and second free lists of each participant was calculated using the Jaccard Similarity Index. The generalized linear model (GLM) with binomial errors and stepwise approach was used to analyze the effects of age and external stimuli on information collection when comparing free lists applied at different times.
Results: Participants' age influenced the information that the free lists collected, demonstrating that the older the participants, the lower the similarity among the free lists. Among the external stimuli analyzed, only the presence of third parties influenced the content of the free lists at the time of the interview. However, contrary to expectations, third-party presence positively influenced the similarity of the lists.
Conclusion: The results show that the studied variables age and third-party presence can influence the capture of knowledge. These findings warrant future research into the influences' causes and their potential mitigation, e.g., by isolation or by breaking the medicinal plant domain into focused sub-domains and conducting simpler, successive free-lists, which can mitigate memory issues.
Keywords: Data collection; Ethnobiological methods; Ethnobiology; Ethnobotany; Medicinal plants.