Much of the research investigating people’s performance on making formal judgements could lead one to conclude that humans are fundamentally irrational in their decision making. Is this a reasonable conclusion?

The ability to make rational decisions and to use logical reasoning has been studied since the Ancient Greeks. The philosopher, Aristotle (cited in Oaksford, 2005), suggested that it was this faculty that separated humans from other animals. On an everyday basis human beings have to make a number of decisions, yet it was not until the 1950’s that psychologists began to study this phenomenon with any intensity, largely due to the dominance of the behaviourist paradigm, in which behaviours were explained in terms of stimulus-response associations to external stimuli, and thus cognitive processes such as decision-making were not recognised. This essay reviews more recent psychological research concerning decision-making, in order to establish whether or not humans are truly rational beings.