This paper examines the issue of how under three year-olds learn the rules of appropriate behaviour in the light of sociocultural, attachment, social learning, ecological theory and sociology of childhood theories. Discipline involves teaching children how to behave acceptably in their family and society, while physical punishment is the use of pain for the purpose of correcting children's behaviour. Research suggests that physical punishment is not necessarily effective in causing compliance, and that the long-term effects of punishment include aggression, poorer intellectual performance, diminished attachment to parents, anxiety, depression, and impaired conscience development. Effective discipline includes a positive, firm and demanding style of parenting; warm and reciprocal parent-child relationships; clear communication with children and reasonable expectations; use of reasoning and explanation; firm, consistent and fair rules; positive consequences for good behaviour; mild non-physical punishment for bad behaviour; and setting up appropriate contexts to encourage good behaviour.