The sunk cost effect previously has been demonstrated with sunk costs of money, but not of time. The present studies explored the potential for a sunk "time" effect by using both the questionnaire method and a behavioral method. The results of the questionnaire experiments (Experiments 1-5) suggest that a sunk time effect does exist, and that certain qualities of the sunk time, such as how fun or boring it is, might impact the effect. The results of the behavioral experiments (Experiments 6-9) also generally suggest a sunk time effect. Some of the behavioral experiments tested the prediction that personal responsibility for initiating sunk cost is a prerequisite of the sunk time effect. The results of Experiment 6 support the prediction while the results of Experiment 8 counter it. Experiment 9 indicates that sunk effort might have been relatively prominent in Experiment 8, leaving open the possible role of personal responsibility, and Experiment 7 suggests that where personal responsibility is a necessary precursor, it is commitment to a long sunk time, rather than mere choice, that heightens persistence. The results are discussed in terms of self-justification theory as well as other theories that may account for the sunk cost fallacy