Lightness and Brightness and Other Confusions

Perception
Processing
Recognition
Transduction
Action
Proximal stimulus
Distal stimulus
Figure 6. The visual process as a circle. (After Goldstein)
Goldstein emphasizes that the process is a lot more complicated and dynamic
and could also be described as a circle (above). In this circle of interactions,
as in the linear representation, the prime cause of visual perceptions is the
distal stimulus. The arrows show the main direction of processing (bottom
up). I have added the weaker anti-clockwise arrows to indicate that there is
also some signalling from the top down, from the higher cortical levels to the
lower. How much of this is taking place and what its effects on seeing are is
still unclear. It seems obvious, though, that our actions influence recognition,
which in turn influences perception. The diagram probably needs to be three
dimensional to depict the process of interactions more faithfully.
Where does seeing come into this? How to define it? According to the above
chart, more than half of the visual process occurs in the brain. Examined as
neural processing, perception proper occurs quite late in this chain. Does
seeing require recognition and does recognition involve conscious experience?
We are faced with this question in the following examples. Richard
Gregory says that the peripheral areas of the retina can produce a perception
of movement in the field of vision without perception of form: “Movement is
seen, but it is impossible to identify the object, and there is no colour” … and
furthermore “When movement stops the object becomes invisible.” (Gregory
2003). So we still perceive – and perhaps see – the movement, if not the
object. But consider this: “The extreme edge of the retina is even more primitive:
when it is stimulated by movement we experience nothing; but a reflex is
initiated, rotating the eye to bring the moving object into central vision,
bringing our highly developed foveal region into play for identifying the object.”
(Ibid., my emphases). We do not see the movement, but we react to it.
Only after that we may see the object.
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