218 A CREATIVE COGNITIONLikewise, as we move around a chair, the line cluster that is picked up
from the front will co- vary in space and time with the line cluster emerg-
ing from the edge or back of the seat. Th e shared, overlapping, sets of
par ameters form an attractor at a higher level. Th is, in my view, is how
object concepts are formed as the basis of knowledge. Th ey furnish tre-
mendous predictability when dealing with the fuzzy nature of experi-
ence in changeable environments.
Viewing concepts and knowledge in this way, rather than as stored,
ready- made images, suggests that what we perceive can be diff er ent
from what we sense. We use the stored grammars to go beyond the in-
formation given. Th is is confi rmed in the fascinating research on visual
illusions.
We have experienced that strange perception of wheels appearing to
rotate backward when the vehicle they carry is clearly going forward. In
the well- known Kanizsa triangle, we add lines where the stored par-
ameters in our networks predict them to be. (It has also been shown, in-
cidentally, that neurons in the visual cortex fi re as if the lines really were
pres ent). Th e fl uidity of the dynamics may also explain the possibility of
two or more rival attractors competing for the sensory input. For exam-
ple, the Necker cube illusion appears as an image that fl ip- fl ops between
two or more equally suitable possibilities, fi rst one face at the front, then
the other (fi gure 7.2).
Richard Gregory argued for many years that visual illusions arise
from the restructuring of current experience from stored knowledge.
He showed, for example, that patients recovering from lifetime blindness
are not susceptible to typical visual illusions.^16 Presumably, this is
FIGURE 7.2
Visual illusions: the Kanizsa triangle and the Necker cube.This content downloaded from 139.184.14.159 on Tue, 17 Oct 2017 13:54:24 UTChttp://www.ebook3000.com