The main purpose of this study was to examine how the differences of contribution influenced the task perception and person perception, when subjects failed at a cooperative task. The second purpose was to examine the correlation between the changes of four variables of personal traits and the causal attribution, and the contribution to the task. The subjects were 36 undergraduate and graduate females. Two students made a pair and were to guess together the shape of the figure under the panel. Three experimental conditions were made, and students were randomly divided into one of the conditions. In the E condition, the contribution of two students of a pair were at the same level. A student in the H condition made a pair with a student in the L condition. Students of the H condition had a higher contribution than students of the L condition. The main findings were as follows: the perceptions of task and partners, and causal attribution of failures were formed differently in the three conditions of contribution. In the four personal traits, the selfesteem variable was seen the most affected by the contribution conditions.