Department of Anthropology and Center for Behavior, Evolution, and Culture, University of California, Los Angeles, California, USA.
Department of Psychology, California State University, Channel Islands, Camarillo, California, USA.
Folia Primatol (Basel). 2021;92(3):164-174. doi: 10.1159/000516315. Epub 2021 May 11.
Researchers frequently use focal individual sampling to study primate communication. Recent studies of primate gestures have shown that opportunistic sampling offers benefits not found in focal individual sampling, such as the collection of larger sample sizes. What is not known is whether the opportunistic method is biased towards certain signal types or signalers. Our goal was to assess the validity of the opportunistic method by comparing focal individual sampling to opportunistic sampling of facial and gestural communication in a group of captive chimpanzees (Pan troglodytes). We compared: (1) the number of observed facial and gestural signals per signal type and (2) the number of observed facial and gestural signals produced by each signaler. Both methods identified facial signals, gesture signals, and gesture signalers at similar relative rates, but the opportunistic sampling method yielded a more even distribution of signalers and signal types than the focal individual sampling method. In addition, the opportunistic sampling method resulted in larger sample sizes for both facial and gestural communication. However, the opportunistic method did not allow us to calculate the signals per time for each individual, which is easily done with the focal individual method. These results suggest that the opportunistic sampling method is (1) comparable to the focal individual sampling method in multiple important measures, (2) associated with additional sampling benefits, and (3) limited in measuring some variables. Thus, we recommend that future studies use a mixed-methods approach, as focal individual and opportunistic sampling have distinct strengths that complement each other's limitations.
研究人员经常使用焦点个体采样来研究灵长类动物的通讯。最近对灵长类手势的研究表明，机会主义采样提供了焦点个体采样所没有的好处，例如可以收集更大的样本量。目前尚不清楚机会主义方法是否偏向于某些信号类型或信号者。我们的目标是通过比较圈养黑猩猩（Pan troglodytes）群体中的焦点个体采样和面部及手势通讯的机会主义采样，评估机会主义方法的有效性。我们比较了：（1）每种信号类型的观察到的面部和手势信号的数量，以及（2）每个信号者产生的观察到的面部和手势信号的数量。两种方法都以相似的相对速率识别了面部信号、手势信号和手势信号者，但机会主义采样方法产生的信号者和信号类型的分布比焦点个体采样方法更均匀。此外，机会主义采样方法使面部和手势通讯的样本量都更大。然而，机会主义采样方法不允许我们计算每个个体的每个时间的信号，而这可以通过焦点个体采样方法轻松完成。这些结果表明，机会主义采样方法（1）在多个重要指标上与焦点个体采样方法相当，（2）与额外的采样优势相关，（3）在测量某些变量方面受到限制。因此，我们建议未来的研究采用混合方法，因为焦点个体采样和机会主义采样具有互补的优势，可以相互补充彼此的局限性。
