1, the imbalance of individual physical and mental development is manifested in two aspects, one is the imbalance of development speed, and the imbalance of change and development at different ages. For example, the height and weight of teenagers have two growth peaks, the first peak appears in the first year after birth, and the second peak is in the puberty. In these two peak periods, the development of height and weight is much faster than usual. Second, the development in all aspects is uneven. Physiologically, for example, the nervous system and lymphatic system mature first, and the reproductive system matures later. Psychologically, mature perception comes first, mature thinking comes last, and mature emotion comes last.

The individual difference of individual physical and mental development refers to the difference of development degree and speed between individuals and between different aspects of individual physical and mental development.

2. Imbalance refers to the change or development speed of "individual's own different stages". For example, there is a critical period, and adolescence develops rapidly. Everything is for yourself.

Individual difference refers to the physical and mental development between individuals. For example, there are differences in personality and psychological characteristics or intellectual development between different children.