During the first two years of life, an infant is in the sensory-motor stage of cognitive development, according to the developmental theorist Jean Piaget. Your child explores his environment through sensory (e.g. seeing and hearing) and motor (e.g. sucking and grasping) contact.
By fifteen months, a child jabbers loudly and freely and speaks two to six or more recognisable words in correct context. He may be able to understand and obey simple instructions and can make animal sounds. He will be able to know parts of his body, and will fetch and carry things. If shown how to, he may be able to build a tower of two blocks.