While various studies have related susceptibility to the Mueller-Lyer illusion to mental health, to developmental maturity, and to self-differentiation, there have been no studies in which susceptibility to the illusion has been related to a wide spectrum of self-concept dimensions. It is one of the purposes of the present study to analyze susceptibility to the Mueller-Lyer illusion as a function of errors in self-perception. To the extent that an individual suffers conflicts with regard to his self-concept, in any of its significant dimensions, it is expected that he will suffer a greater susceptibility to the illusion.

This study has as its objectives: (1) the determination of the degree of relationship between achievement in the study of English as measured by a standardized English achievement test and achievement in the study of foreign languages as measured by teacher's grades; (2) the determination of the amount of contribution to such a relationship of the achievement in various functional areas in the study of English as measured by the subtests of the English achievement test.

The concept of level of aspiration bears directly on goal setting behavior; it is a convenient and important variable in understanding human motivation in a variety of situations. Thus it was the purpose of this study to investigate the relationships between levels of aspiration and the psychological needs of achievement, dominance, autonomy, change, and aggression.