Dottorato in PSICOLOGIA E SCIENZA COGNITIVA

Titolo della tesi: Attraction effect and sequential sampling models of decision making

The attraction effect (AE) in multi-attribute and multi-alternative decision making reflects the context-dependent violation of some economic axioms that have long been considered as basic features of rational choice. Human decisions can be biased by irrelevant information, and contexts effects have shown the influence on option evaluation resulting from its relational properties with other alternatives in the choice set. Specifically, the attraction effect emerges when adding a seemingly irrelevant option (decoy) to a binary choice shifts preference towards a target option. This suggests that choice behaviour is dynamic, i.e., choice values are developed during deliberation, rather than manifesting some pre-existing preference set. Whereas several models of multialternative and multiattribute decision making consider dynamic choice processes as crucial to explain the attraction effect, empirically investigating the exact nature of such processes requires complementing choice output with process-tracing data. The studies described in this thesis focus on asymmetrically dominated decoys (i.e., decoys that are clearly inferior to a target option) to examine the attentional and comparative processes responsible for the attraction effect. Results document its influence in several multiattribute context such as intertemporal, probabilistic, consumer and preferential decision making. Through a series of behavioural and process tracing paradigms (i.e., eye-tracking), it is shown that the decoy option can affect people’s preferences in two different and not mutually exclusive ways: by focusing the attention on the salient option and by increasing comparisons over the choice dominant pattern. Although conceptually and procedurally distinct, both pathways for decoy effects produce an increase in preferences for the target option, in line with attentional and dynamic models of decision making. This thesis substantially contributes to the theoretical and empirical development of sequential sampling models of decision making, by investigating the comparative approach, response times, subjective values fluctuation, time course of decisions, and choice architecture within a broad range of multialternative and multiattribute decision making scenarios. Moreover, the last study analyses context effects in non-humans animals’ decision making: both attraction and repulsion effects were observed in capuchin monkeys (Sapajus spp.), a Central and South American primate species that separated from Homo sapiens approximately 35 million years ago, thus suggesting that comparative processes in decision making are evolutionarily ancient and shared across various species. The conclusions summarize the implications of this series of interconnected studies for understanding the multifaceted role of context and choice architecture in decision making.