One of the more compelling arguments proposed, is language and the theory of mind. Theory of mind (TOM) refers to the cognitive ability to represent, conceptualize and reason about mental states. In this retrospect, the ability to identify behavioral patterns or the ability to make sense of the minds of others is also considered TOM. The TOM is a trait unique to humans, though in recent studies, researchers have found that certain apes are seen to be on the brink of developing their own TOM.

As conceptual framework, TOM is the reason for the cognitive aspect of human behavior. This framework treats perceptual input as perceptual stimuli – classifying it as a belief or an intentional action warranting response. The framework further dictates appropriate response to such perceptual stimuli – in the form of inference, prediction and explanation.

Theory of Mind is not present in humans from the start – rather the cognitive framework is slowly honed as the child grows into adulthood. At different ages, there is a change in the developmental stage of TOM in humans. Miller (2006) crafted a table that outlined a timeline for the development of different aspects of theory of mind, which can be seen below.

Past research has shown that there is a significant development in TOM between the ages of 3 to 4 years old. At the stage of early concept formation (between infancy to 2 years of age), there is a consistent development of TOM in children in different areas: perceptual sensitivity to goal-directed action and the ability to infer intention from human behavior. After which, the TOM sees a development in the conceptual understanding of desire and belief (between 2 to 3 years of age). The conceptual understanding of false belief is developed at 4 years of age.

The ability to understand false beliefs is commonly attributed as the significant milestone in the development of TOM. This is why there is a significant development in TOM as a child turns 4, since the child now is able to differentiate false beliefs from beliefs. There is a simple task used to test whether a child has achieved this conceptual understanding, also known as the false beliefs task.

In this task, the child is given the following scenario:A boy leaves chocolate on a shelf and then leaves the room. His mother puts it in the fridge. The child would be tasked to identify whether the boy would look first for the chocolate when he returns to the room. To pass the task, the child must understand that the boy holds the false belief that his chocolate is still on the shelf and would look there first, instead of heading for the fridge. By passing the false beliefs test, it shows that the child is able to understand that his own mental representation of the situation is different from the mental representation of another, and the child should predict the behavior of another accordingly, based on their mental representation.

It has been observed that as a child grows older, the instances in which they are able to accurately predict the behavior of another through the false beliefs test increases. At age 4, the likelihood for them to be able to identify the correct location of the chocolate would increase, compared to when they were three years old.