Object permanence is the understanding that objects and events continue to exist when they cannot directly be seen, heard or touched.

A child may insist on drinking a big glass of juice, preferring a tall narrow glass to a short broad one, even though both might be holding the same amount of juice.

Phenotype is the way an individual’s genotype is expressed in observable and measurable characteristics. Phenotypes included physical traits, such as height, weight, eye and skin colour, and many of the psychological characteristics such as intelligence, creativity, and personality. These observable characteristics of an individual are the result of the interaction between the persons inherited traits and the environment.

Centration is a stage belongs to preoperational stage of Piaget theory. It is focussed on single characteristic or feature for understanding an event. For example child may insist on drinking a big glass of juice preferring a tall narrow glass to a smart broad one.

The exosystem includes events in social settings where the child does not participate directly, but they influence the child’s experiences in the immediate contact. For example, the transfer of father or mother may cause tension among the parents which might affect their interactions with the child or the general amenities available to the child like quality of schooling, libraries . medical care, means of entertainment, etc. It is different from chromosystem and macrosystem on the following grounds:

Chronosystem involves events in the individual life course and socio-historical circumstances of the time such as, divorce of parents or parent’s economic setback and their affect on the child.

Macrosystem includes the culture in which the individual lives.