Time Spent Thinking in Online Chess Reflects the Value of Computation.

Human planning tends to be efficient, focusing on a relatively small number of options when considering future paths. Recent proposals have suggested that this efficiency reflects intelligent deployment of the limited resources available for planning. A prediction of this and related proposals is that when individuals spend time thinking should depend on the benefits and costs of additional computation. We tested this hypothesis by measuring how much time humans spent thinking before acting in over 12 million online chess games. Players spent more time thinking in board positions where additional computation was more beneficial. This relationship was greater in stronger players, and was strengthened by considering only the information available to the player at the time of choice. A simple model based on measuring the actual cost of spending time thinking in online chess was able to capture qualitative features of this relationship. These results provide evidence that the amount of time humans spend thinking is appropriately sensitive to the value of computation.