The purpose of this study is to determine the intervention method among individuals by analyzing and categorizing how the performance on a dual task decreases when the required attentional load increases through a validation test. The validation test consisted of a dual task with two different tasks. As a result of the validation test, we hypothesized that there exists a one-sided state in which response delays occur in the low-priority task during the transition from the dual-task state, where the task is performed stably, to the saturation state, where all tasks are disrupted. Therefore, considering the one-sided state, we classified participants' attention distribution state into four states during the dual-task and analyzed the transition of the collapse model for individual. As a result, we were able to identify the one-sided state, classify the collapse models of the dual-task into three patterns, and propose appropriate timing of intervention methods for each pattern.