Body part as an object  Body part as an object (BPO) mime gestures occurs when a mime artist or other individual substitutes a part of their body - usually arms, fingers, or hands - to be part of an object they are miming. Miming uses representational gestures, meaning they are used to convey a message to others without the use of speech. A commonly used example of BPO miming is demonstrated by an individual using their finger to represent a toothbrush while acting out brushing their teeth. In studying gestures from a psychological, psycholinguistic, and/or neuropsychological context, pantomimes can be distinguished by how they are carried out. For example, BPO mime gestures are differentiated by the insertion of a body part to help represent the object itself. Conversely, Imaginary object (IO) pantomimes occur when an individual mimes the use of an object as though the object were actually present. Using a similar example to above, an IO pantomime occurs as an individual pretends to brush their teeth by positioning the hand and fingers as though the toothbrush were actually in their hand: they are pretending the object is actually present. BPO, and BPO measures particularly, are notable in that they have proven useful in studying cognition (e.g. language development, developmental psychology), and in identifying - and to a limited degree, in treating - cognitive impairment (e.g. aphasia, apraxia, schizophrenia etc.). BPO pantomimes are generally seen more in young children (3–5 years old) and those with brain damage. There are many theories as to why BPO may be prevalent in these populations. This includes disruptions in the conceptual or temporal-spatial stages in the process of learned gestures, an impairment of conveying hand-posture of tool use, and a poor representation of an external objects. IO pantomimes are seen as much more complex than BPO pantomimes because they must have a strong mental representation of the object to be used and understood. An individual cannot garner any supportive information from the environment, and must know and understand the properties of the object to manipulate it as though it is in use, even though it is not physically present. There have been many models attempting to explain how gestures are related to semantic concepts, such as imagery and speech. The "Sketch Model" relates semantic concepts and gestures to one another. It posits that gestures and speech have the common purpose of communication, and thus are represented at the same conceptual level.