"Perhaps there are many "nows" of varying duration, depending on just what it is we are doing. We must face up to the fact that, at least in the case of humans, the subject experiencing subjective time is not a perfect, structureless observer, but a complex, multilayered, multifaceted psyche. Different levels of our consciousness may experience time in quite different ways. This is evidently the case in terms of response time. You have probably had the slightly unnerving experience of jumping at the sound of a telephone a moment or two before you actually hear it ring. The shrill noise induces a reflex response through the nervous system much faster than the time it takes to create the conscious experience of the sound. It is fashionable to attribute certain qualities, such as speech ability, to the left side of the brain, whereas others, such as musical appreciation, belong to processes occurring on the right side. But why should both hemispheres experience a common time? And why should the subconscious use the same mental clock as the conscious?"