Why are we so bad at sticking to schedules? The explanation can’t just be laziness or procrastination, since in many of these cases the employees were working at full productivity. Instead, psychologists tend to blame a cognitive quirk called the planning fallacy, which leads us to consistently underestimate how long it will take us to complete a project.
The concept of the planning fallacy was first introduced by the Nobel Prize-winning psychologist and economist Daniel Kahneman and his collaborator Amos Tversky in the 1970s, who were inspired by the habits of their colleagues. They were surprised to note that their colleagues routinely underestimated how long a project would take to complete even after they had missed many deadlines on similar projects in the past. They weren’t learning from their errors.
Surveys confirm that the planning fallacy is astonishingly common. In schools and universities, it can be seen among both staff and students. In IT, surveys suggest that fewer than one third of projects meet their initial deadline. In industrial research and design, projects take about 3.5 times as long as expected. In each case, previous failures did not appear to improve their chances of meeting a deadline in the future.
The problem is that our failures to meet deadlines often come from less predictable, more general factors – such as new distractions from other tasks, difficulties with travel or gaining the necessary supplies, or illness – that could all contribute to a delay. It’s these kinds of difficulties that probably caused us to miss deadlines in the past – and recognising that fact could help us to pre-empt some of those issues in the future.
By focusing too much on the highly specific details of our current task and ignoring our past experiences, however, we fail to take those possibilities into account.