Progress Decisions Involving Time: Sunk Cost or Completion Effects

Five studies involving seven samples were conducted to examine the effects of sunk time in progress decisions. Previous research on sunk time in progress decisions has failed to control for completion effects. Studies 1a and 1b found strong evidence for completion effects and weaker effects for sunk time effects on probability of continuing. In Studies 2a and 2b, we expanded our sunk time scenarios to use multiple types. We found evidence for sunk time and completion effects on probability of continuing. An additional analysis, however, found that the sunk time effect was larger when the progress decision involved a goal focused on the accomplishment of a project (e.g., writing a paper for class), as opposed to a goal focused on enjoyment (e.g., watching a television show). Study 3 found that both sunk time and completion effects were present in progress decisions focused on the accomplishment of a project. These effects were present even when participants were informed that there was sufficient time to complete an alternative project. Study 4 failed to find a sunk time effect in a behavioral study, and Study 5 replicated Study 4 using a vignette format. Overall, these results provide some evidence of sunk time effects in progress decisions, but the effect appears to be small and may be due, at least partially, to completion effects.