Why do we chew stuff(like pens) when concertating or thinking about something?
The act of chewing on a pen or pencil has been linked to the oral phase of childhood development and self-comforting [1]. It has been suggested that pen chewing occurs when we are anxious or stressed [1]. When presented with an idea, our mind will first grasp it and then "chew" on it [2]. Our conscious mind breaks it down into its component parts, tastes it, then swallows it into the subconscious for final assimilation [2]. As food works with digestion, so too do perceptions work with the mind [2].
There are many reasons why people chew on pens when they are thinking or concertating. Psychologists have suggested that the act of pen chewing is self-comforting and occurs as a result of feeling anxious or stressed [1]. From a psychophysiologic perspective, chewing and crunching are natural outlets for inborn aggression [2]. Like the lion, human beings have a distinct measure of innate aggression, and developmental psychologists often see this energy as first experienced through the infant's desire to bite [2]. Psychologists call the original oral-aggressive act the "hanging-on bite" to the breast [2]. This is a biting that establishes confluence with the mother. The baby must actively hold on for nourishment and will often keep holding on even when mama has had enough [2]. The tension it experiences when separated from the mother before it's fully satisfied is typically expressed through crying, screaming, and facial contortions [2]. Just as a dog clenches its teeth when angered or challenged, so too do human beings channel aggression through the face [2]. From an evolutionary perspective, the process of biting and chewing allows for the release of what psychologists call dental aggressive urges [2].