Abstract: The choice of time markers plays a key role in the research of psychological development. Developmental psychologists usually use the two important time markers, chronological age and schooling grade, to map the development of various psychological characteristics, when they trace one group of young children or compare different groups of young children. Chronological age is used to mark the time of psycho-physiological maturation and accumulated experiences acquired out of formal school. The schooling is used to indicate accumulated experiences of schooling. Researches and educational practices strongly suggest that these two markers would be the two different sources of variances of psychological development, and could be decomposed and studied by well-planned experimental design and appropriate statistical methods. In the present study, three personality traits (Neurotics, Extraversion, and Conscientiousness) of high school students are studied in terms of decomposition of chronological ages and schooling grades, in order to answer to some extent the classical and enduring debate on whether the bio-genetic or social cultural factors determinate personality development.
The measures of the three personality traits come from the Chinese version of NEO-FFI. There were selected because there could be used to measure personality of Chinese high school students with satisfactory psychometric characteristics. In the present study, a valid sample of 998 students who were aged from 12 to 19, and recruited from all six grades of five high schools in Dalian city, made responses to the measuring items in a group manner. The preliminary statistical analysis showed that the three factors have high internal consistencies and high item and factor congruence coefficients, and thus made further comparisons across different ages and grades possible. The partial correlation method, multiple regression method, and same-grade-same-age method were adopted in order to decompose the grade and age effects from variance of personality measurement.
The results of comparisons manifested that the age and grade effects can be indeed decomposed from each of the three personality traits for students at different age and different grade. There is a negative age effect on E factor and, particularly, a negative grade effect on C factor. These may suggest that E would be more related to genetic-biological factor, while C to environmental factors. The above results may indicate also that the methods of effect decomposition analysis can not only be applied to cognition development, but also to other psychological development such as personality as well. They could help psychologists to understand development more clearly by not confusing the age and grade effects in their studies

Key words: chronological age, schooling, time marker