Classifying strategy use in multi-attribute subjective choice: Application to conjoint experiments in political science

Conjoint experiments are extensively used across multiple disciplines to make inferences about preferences over multi-attribute alternatives. Much previous research has analyzed the importance of attributes at the aggregate level. Here, we focus on understanding individual-level behavior and, specifically, on strategy use. We present a novel Bayesian cognitive model that infers individuals' strategy use by performing attribute weight inference (how important an attribute is), attribute level inference (which value of the attribute is favored), and latent-mixture inference to classify strategy use. We then validate and apply our model to two conjoint experiments (total N = 3762) focusing on three political domains (attitudes towards immigrants, political candidates, and climate policy). From a substantive standpoint, we find that the majority of subjects use heuristic strategies in all conditions and that approximately 60% of subjects use different strategies depending on the political domain. Our model additionally highlights how aggregate-level inference on the weight of an attribute can be meaningfully decomposed by individual differences in strategy use and preferences over attributes. Specifically, we demonstrate clear multimodality in the distribution of attribute weights across individuals for all political domains and conditions, raising questions about how to appropriately contextualize information that is aggregated at the population level. In addition, our experiments include a set of experimental design manipulations that increase different dimensions of complexity in the conjoint experiments and show their impact on strategy use. This work has important implications for understanding how to interpret and generalize results from conjoint experiments, in addition to contributing to the strategy modeling literature. Further, we highlight how researchers can apply our model to their own conjoint experiments for both applied and methodological research aims.