A self-control procedure that involved a later onset of a stimulus signalling a small reinforcer within the waiting time for a larger reinforcer was investigated to determine a point of shifting preference and a discounting function as the delay varied. The results from Experiment 1 to Experiment 3 showed exclusive impulsive choices regardless of the delay. In order to examine if the results were due to the procedure and the parameters, or the species used, Experiment 4 attempted to obtain shifts in preference using simultaneous onset of stimuli with the same species. The results demonstrated no changes in preference but an increase in proportion of self-control choices was shown. Due to the limited information from the replicated studies, the accounts for the results could not be concluded. The explanations derived from choice models seemed most plausible, but limitations of the choice models were discussed.