54 Informational environments
Strategy thus accounts for only one of two types of cases of illusion (see Purves
et al. 2011, 15590). Second, the Empirical Strategy remains exclusively concerned with isolated perceptual qualities, such as brightness or perceived angles,
length and motion rather than more complex perceptual affairs in which seeming
illusions are mended in the course of perceptual investigation, and in which an
object with complex and perhaps multi-modal perceptual qualities is relevant to
the organism in certain ways. In contrast, Gibsonian ecological psychology refers
to the environmental context and the additional cues it provides to the organism,
so as to correct for perceptual ambiguities of the second, the Berkeleyan kind.
Despite these limitations, the Empirical Strategy is correct in suggesting that a
perceptual illusion, in terms of a prima facie mismatch between perceptual quality
and measurable values for some physical variable, may serve adaptive functions.
A certain class of perceptual illusions, one that is not clearly distinguished from
instances of misperception by Gibson, can thus be accounted for. A necessary precondition for the accomplishment of the adaptive function of a perceptual illusion
will be that the illusion is embedded in the context of an environment that is stable
enough to allow the organism to handle world affairs with some reliability and
within the bounds of his constitution and abilities. Genuine misperception occurs
only if and when either the conditions within organism or environment depart
from what he is adapted or accustomed to or if and when the perceiving organism
fails to grasp what can or should be done with the object in question. Perceptual
illusions, if and when they have acquired an adaptive function, may actually both
be a constituent of the perception of affordances and provide accurate information
about some world affair to the perceiving organism. Under normal circumstances,
perceptual illusions of the kinds discussed previously, for their very regularity and
their possible adaptive function, have precious little to do with the misperception
of affordances but, very much to the contrary, with helping the organism to get
right about some object what he needs to get right.
Any insect replica in an experiment in frog vision that shares most or all perceivable (i.e. ‘frog-perceivable’) surface properties with edible insects will be
perceived and treated identically, however, without being nourishing to the frog.
Such ambiguity can be resolved only if other cues as to the insect replica’s identity
as a replica are or become available to the frog. These are situations of genuinely
ambiguous information for perception that is prone to end in misperception – but
misperceptions, so understood, are certainly not cases of perceptual illusion of
any kind. Misperceptions of this kind will be difficult to assess for any theory
of perception that does not spell out the specific conditions for perception with
respect both to its historical and to its ecological context.
If, in turn, studies in the measurement of affordances are right in assuming that
the information relevant to perception normally is intrinsic, the perceiving organism’s correct grasp of his relation to the environment will override any apparent
mismatch between perceptual qualities and the absolute values for some physical
variable that could be measured by an external observer. Misperception, then, can
only be misperception of objects in their entirety, not of their measured properties. In
Gibson’s terms, such misperceptions would be misperceptions of affordances – not,
Strategy thus accounts for only one of two types of cases of illusion (see Purves
et al. 2011, 15590). Second, the Empirical Strategy remains exclusively concerned with isolated perceptual qualities, such as brightness or perceived angles,
length and motion rather than more complex perceptual affairs in which seeming
illusions are mended in the course of perceptual investigation, and in which an
object with complex and perhaps multi-modal perceptual qualities is relevant to
the organism in certain ways. In contrast, Gibsonian ecological psychology refers
to the environmental context and the additional cues it provides to the organism,
so as to correct for perceptual ambiguities of the second, the Berkeleyan kind.
Despite these limitations, the Empirical Strategy is correct in suggesting that a
perceptual illusion, in terms of a prima facie mismatch between perceptual quality
and measurable values for some physical variable, may serve adaptive functions.
A certain class of perceptual illusions, one that is not clearly distinguished from
instances of misperception by Gibson, can thus be accounted for. A necessary precondition for the accomplishment of the adaptive function of a perceptual illusion
will be that the illusion is embedded in the context of an environment that is stable
enough to allow the organism to handle world affairs with some reliability and
within the bounds of his constitution and abilities. Genuine misperception occurs
only if and when either the conditions within organism or environment depart
from what he is adapted or accustomed to or if and when the perceiving organism
fails to grasp what can or should be done with the object in question. Perceptual
illusions, if and when they have acquired an adaptive function, may actually both
be a constituent of the perception of affordances and provide accurate information
about some world affair to the perceiving organism. Under normal circumstances,
perceptual illusions of the kinds discussed previously, for their very regularity and
their possible adaptive function, have precious little to do with the misperception
of affordances but, very much to the contrary, with helping the organism to get
right about some object what he needs to get right.
Any insect replica in an experiment in frog vision that shares most or all perceivable (i.e. ‘frog-perceivable’) surface properties with edible insects will be
perceived and treated identically, however, without being nourishing to the frog.
Such ambiguity can be resolved only if other cues as to the insect replica’s identity
as a replica are or become available to the frog. These are situations of genuinely
ambiguous information for perception that is prone to end in misperception – but
misperceptions, so understood, are certainly not cases of perceptual illusion of
any kind. Misperceptions of this kind will be difficult to assess for any theory
of perception that does not spell out the specific conditions for perception with
respect both to its historical and to its ecological context.
If, in turn, studies in the measurement of affordances are right in assuming that
the information relevant to perception normally is intrinsic, the perceiving organism’s correct grasp of his relation to the environment will override any apparent
mismatch between perceptual qualities and the absolute values for some physical
variable that could be measured by an external observer. Misperception, then, can
only be misperception of objects in their entirety, not of their measured properties. In
Gibson’s terms, such misperceptions would be misperceptions of affordances – not,