The focusing effect (or focusing illusion) is a cognitive bias that occurs when people place too much importance on one aspect of an event, causing an error in accurately predicting the utility of a future outcome.
People focus on notable differences, excluding those that are less conspicuous, when making predictions about happiness or convenience. For example, when people were asked how much happier they believe Californians are compared to Midwesterners, Californians and Midwesterners both said Californians must be considerably happier, when, in fact, there was no difference between the actual happiness rating of Californians and Midwesterners. The bias lies in that most people asked focused on and overweighed the sunny weather and ostensibly easy-going lifestyle of California and devalued and underrated other aspects of life and determinants of happiness, such as low crime rates and safety from natural disasters like earthquakes (both of which large parts of California lack).
A rise in income has only a small and transient effect on happiness and well-being, but people consistently overestimate this effect. Kahneman et al. proposed that this is a result of a focusing illusion, with people focusing on conventional measures of achievement rather than on everyday routine.
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