Abstract: This paper attempted to study the influence of pre-composition planning time on the pre-compositionplanning effect by the method of combining natural experiment and laboratory experiment. Our studydiscovered that the composition form determined the planning time, which in turn influenced theplanning effect which then determined the composition form. This indicated that with both the plan andthe external representation, the plan itself played a decisive role in the relations between the limitedtime for planning and the planning form. A more complicated case about the effect of the externalrepresentation emerged when the plan existed, i. e. the external representation is of great significancewhen there is plenty of time for planning. In contrast, the plan is of greater significance than theexternal representation when there is not enough time to plan.

Key words: plan, time, form, external representation, composition