By the end of the 19th centuryÉ..
q
Different sensations (pain, touch, smell, sight, hearing)
are mediated by different physiological
structures
in the nervous system
q
Within a modality (e.g. sight) different nerve fibres respond selectively to different stimuli
(e.g. different ranges of
wavelength)
q
Perception is affected by in-built knowledge of the world, i.e. is not a simple transformation
of the raw sensory input