According to Erik Erikson’s Psychosocial Development Theory, major conflict in infancy period is trust vs. mistrust. Major conflict in early childhood period is autonomy vs. shame and doubt. Major conflict in play age period is initative vs. guilt. Major conflict in shool age period is industry vs. inferiority. Major conflict in adolescence period is identity vs. role conflict. Major conflict in young adulthood period is intimacy vs. isolation. Major conflict in middle adulthood period is generativity vs. stagnation. Major conflict in old age period is ego integrity vs. despair.

Crawling, sitting alone and taking first steps are the signs of gross motor skills, which include activities and movements that result from large-muscle development. In order to develop gross motor ski­lls, an infant needs to develop sk­ills to control hi­s/her posture. Fine motor skills are involved in small muscle activities and movements that occur in the hands and fingers, such as grasping the mother’s finger; reflexes are uncontrolled automatic reactions to external stimuli and they have a survival value; sensory skills occur when external stimuli interact with sensory receptors; and perceptual skills are the analysis and understanding of sensation.

Phallic stage is the most critical psychosexual stage for personality development since it involves the greatest psychosexual conflict, which begins at 3 and lasts until 6-7 years of age. During this stage, the libido is located at the sex organs mainly at the penis. The child discovers his/her own sexuality, gender and social meanings attached to men and women.