One key part of infancy and childhood involves attachment patterns -- how an individual infant and/or child relates to others.
Attachment Theory Resources -- This page, maintained by the Department of Psychology at SUNY-Stonybrook serves as a wonderful resource for the study of attachment.
Frank Sulloway discusses Birth Order, Personality, and the Environment on the Edge Web Site -- Frank Sulloway has offered a provocative new theory of how birth order -- whether one is first-born or later-born -- influences one's personality. In this column he describes and defends his views on the matter, in response to criticism from the developmental psychologist Judith Harris.