Discussion Theory of mind refers to ability to infer full range of mental states, such as desires, belief, emotions, intensions, knowledge, imaginations, and others that enables us to explain and predict other’s behavior (Trevarthen, 1995, p. 48). It is a broad construct that is reflected in numerous kinds of knowledge and skills. Theory of mind develops gradually over time just like language. It builds from foundational, precursor skills to complex understanding of how mental states and behavior interact. Theory of the mind plays an important role in infant cognitive and social development. This paper highlights the importance of theory of mind by describing studies that have been done that have been able to measure theory of mind. The studies are described within three domains of language, attachment and emotion in relation to theory of mind. Language and Relationship with Theory of Mind Language development and theory of mind are interwoven in sophisticated ways. Children at infancy engage in joint attention and indicate appreciation of other’s intensions within the context of communicative acts. Toddlers commence to use mental state terms in more mentalist ways and engage in pretend play (Trevarthen, 1993, p. 48). Young children begin to comprehend that different individuals have different access to information and desires. They listen to and get involved in conversations in individuals predict and explain behavior in terms of desires, beliefs and feelings. Language and theory of mind interact in some of ways. Language and theory of mind both experience rapid and dramatic changes in development during the first 5 years of life. Theory of mind is important for communication through language; language may in turn provide a way to learn about theory of mind. Language is important in development of theory of mind because mental states are observable. Several studies suggest that development of theory of mind in children is influenced by their exposure to speak about mental states. A study by Ruffman (2002, p. 734) discovered that mothers who speak about mental states predicted children’s later theory of mind performance, as did children’s language ability. The study indicates family context to be important in the emergence of talk about mind which begins in the second year. It observes that maternal mental state talk to infants predicted a change in infant’s mental state language 12 months later. The purpose of the study was to analyze ways the family context influences development of infants language about mind. It examined factors related with infant’s exposure to language within the family. it also looked at the causal role of exposure to different modes of mental state talk within family in development of infant’s own mental state language. Children’s earlier theory of performance, however, did not predict later mental state talk by mothers, suggesting a causal role for mothers’ talk about mental states in their children’s theory of mind development. It is not only mothers who may play a role in theory of mind development. Dunn (1991, p. 1352) found that theory of mind understanding at 40 months was correlated with engagement in family talk about feelings and causality, and cooperat