
Americans are faced with a bewildering array of choices. In this lively introduction to psychological research on how people make decisions, Scott Plous focuses on the social aspects of decision making and includes everyday examples from medicine, law, business, education, and nuclear arms control, among other areas. Intended for nonspecialists, this book highlights experimental findings rather than psychological theory and presents information in descriptive prose rather than through mathematics. A unique feature of the volume is the "Reader Survey" that precedes the first chapter. Readers are asked to answer questions that are taken from studies discussed later in the book. This brief (and entertaining) exercise allows readers to compare their answers with the responses people gave in the original studies and to better understand their own processes of choosing. In a comprehensive yet nontechnical presentation, Plous explores the building blocks of judgment and decision making: perception, memory, context, and question format. He contrasts historical models of decision making with recent models that take into account various biases in judgment. In addition, the author examines judgments made by and about groups and discusses common traps in judgment and decision making.
I'd say that if there are several pieces of evidence in favor of some theory and several against, it is hard for people to weigh the entirety of the evidence. Instead they will often pick one salient fact and ignore the rest.
IMO, the "correct" way to study it is through Gary Klein's Recognition Primed Decision Model (RPDM) (https://en.wikipedia.org/wiki/Recognition_primed_decision) and the Naturalistic Decision Making (NDM) Framework (https://en.wikipedia.org/wiki/Naturalistic_decision-making).
For a comprehensive overview of various approaches/models see Thinking and Deciding by Jonathan Baron and The Psychology of Judgment and Decision Making by Scott Plous.