Constantly, psychology is revealing that people have habits that aren't particularly beneficial in our everyday life. Although it's difficult whether the cause is genetic or cultural, both, or something else, the planning fallacy is just another example of am inconvenient human tendency. More specifically, it relates to the observation that individuals typically underestimate the time that it takes to complete a project.
More specifically, there are a variety of examples of this phenomenon, and many of us can turn to examples in our own life whether they be school papers, work assignments, or long-term goals. However, a study in 1994 revealed more details when psychology students were asked to estimate the time required to complete a college thesis. Even when asked the time required to complete the thesis in "the worst case scenario," the average result was higher than the average prediction if everything were to go wrong. Furthermore, individuals who had less confidence in their predictions tended to be more likely to be correct. Contrastingly, those who were extremely overconfident were more likely to be wrong.¹
A variety of factors may contribute to the planning fallacy. For example, an optimization bias may cause people to be unrealistic even when presuming negative circumstances. Additionally, people often fail to consider possible factors that can influence their plans - partially due to the vast amount of variables in life. So when making an estimation, it may fail to include this unrecognized variables. Unfortunately, this tendency can cause individuals to end up in difficult circumstances. For instance, a continued practice of poorly estimating completion times can result in deadlines being missed, work being backlogged, and an increase in personal stress levels, to name a few things.
In some ways, it appears that a lack of confidence tends to make people more realistic. However, that does not mean this makes them more successful. For instance, those who are more confident in themselves may miss their goal, but they could still do better than the less confident individuals who meet their rather long estimation of how long it takes them to complete something. In other cases, a person may simply have experience with doing a similar project and be efficient at determining what the probabilities are with regards to long something will take. When based on past experiences rather than optimism or confidence in oneself, a person may be able to acquire a more accurate assumption of the time required to complete a project. Either way, it's beneficial to reflect upon the planning fallacy to minimize or avoid the impact it can have on one's life.
1. Buehler, Roger; Dale Griffin, Michael Ross (1994). "Exploring the "planning fallacy": Why people underestimate their task completion times". Journal of Personality and Social Psychology (American Psychological Association) 67: 366–381.