Vision, in psychological terms, is a tricky subject to define. Vision is one of the five physical senses (although some claim some or all humans have a less obvious sixth sense), and all senses are defined by how they adequate a stimulus, how the stimulus is transduced, and how the stimulus goes through a “coding” stage.
Adequate Stimulus: What the sensory system is designed to detect (vision equals light).
But… What is light? Light is electromagnetic energy waving its way through space. Visible light, that humans can see, exists with wave lengths ranging from approximately 380 nanometers (the color blue) to 760 nanometers (the color red). However, color exists only in the mind and our perceptions of the electromagnetic waves.
Transduction: The changing of one form of energy into another, and in terms of senses, this means changing the stimulus into a membrane potential.
“Coding”: A system in the brain and eyes that helps to decode which colors are which, what lights are blindingly bright and those that are very dim.
But… Mr.
Science,
whatever are these “codes”? There are two “codes”, one being the
temporal code, which travels from one
neuron to the next. This code detects the
intensity of a light source by measuring the
frequency of our nervous
impulses. The second code is the
special or
anatomic code, which depends on the
location of the neuron. For example, if your
left arm is
touched, your
right arm doesn’t
feel it, and in the case of vision, different neurons and
axons are designated to
different colors.