In simultaneous learning two verbal lists are interlaced for study, with each tested separately. In the present experiments simultaneous learning was used as a means of determining the conditions under which study time or learning resources might be reallocated between lists. One of the lists was called the standard list and remained constant across the conditions of each experiment. The other list, the variable list, was manipulated to produce differences in its difficulty. If performance on the standard task varied as a function of the difficulty of the variable list a shift in study time was inferred. In one experiment the variable task difficulty was changed by manipulating word frequency, stimulus similarity, concreteness, and meaningfulness. These manipulations had little influence on performance on the standard task. However, in another experiment when words were repeated in the variable task, more time was given to the standard. When subjects knew that the variable task was to be tested for recognition they gave less study time to it than when a recall test was to be given. It was concluded that subjects reallocate study time between two tasks being learned simultaneously only when there are obvious differences in difficulty. (Author/RL)