Pretend play encompasses several abilities that coincide with theory of mind. The first two abilities relate to object representation. The child has the ability to mentally represent one object as another. The child also has the ability to understand the paradox, in which the object can represent another, but in essence remains the same object. This means that the child is required to hold two contradicting mental representations of the same object. In 3 year olds, this cognitive ability is evident in pretend play but not in other activities. For example, the child can pretend that a pen is a toothbrush, but when shown an apple shaped soap bar, the child is unable to comprehend the real and apparent features of the object. This inability is referred to as mutual exclusivity bias. However, development of pretend play has been found to correlate with performances in the previous example along with performances in the false-belief task, which also tests a child's understanding of mental representations. Children begin to pass the false belief task at around the age of 4.