Evolutionary biologist Robert Trivers wanted to persuade a potential mate or ally of their good intentions would be better at it if they could deceive themselves without ‘leakage’ of knowledge or intent; and the most efficient way to simulate truth-telling would be to erase internal awareness of the deception. The best liars would be those who were better at lying to themselves because they would actually believe their own deceptions when they made them. They would be more likely to survive and pass on their genes; hence our gift for self-deception.
(It’s not insignificant that the word ‘person’ derives from the Latin word for a mask worn by an actor.) In Goffman’s view, we’re all actors who have half-forgotten that we’re acting. Most of the time we play a double game, aware that others are performing for us and yet believing in the performance at the same time.
As the medical anthropologist Daniel Moerman has documented, one of the important determinants of a drug’s efficacy is the colour of the pill it comes in. When people suffering the symptoms of depression are given the same drug in different colours, they are most likely to get better when the pill is yellow. Sleeping pills, by contrast, tend to be more effective when they’re blue.
In a more recent study, psychologists from New York University asked students to estimate the distance between their own position and a full bottle of water on the table at which they were sitting. Beforehand, they fed some of the students a diet of pretzels to make them thirsty. The thirsty students judged the bottle to be closer than the other students did. Another study revealed that hills appear steeper to us than they actually are, and that this tendency is exaggerated when the observer is old, unhealthy, or wearing a backpack.