Rate of development; development take place at different parts of human body. Rate of development is not uniform.Individual differs in rate of growth and development.Boys and girls have different rates of development.Each parts of the body has its own rate of growth. There are period of great intensity and equilibrium and there are periods of imbalance.Example the rate,manner and timing of language development is different from when and when intelligence works or puberty works.according to suzanne lewis(1957)"every human has unique development and growth rate".so in general development take place at different rates.