Varieties of perception 49
illusions, the normative qualities of my perceptual relation are determined by the
actual match or mismatch between the information that is present and the successful realisation of my abilities to act upon conditions in my environment, not
the illusionary appearances. Getting all the physical properties of an object right
might not be all that important in this respect (properties that Gibson did not care
much about either). This is the basic idea brought forward by one relatively recent
theory in cognitive psychology that has come to be known as the “Empirical Strategy” or, less memorably but more descriptively, the “wholly empirical approach
to perception” (Purves et al. 2001; Purves et al. 2011).
5
In combining an environment-directed outlook with a distinctive set of computational and statistical methods, the Empirical Strategy seeks to explain the peculiarities of perception by reference to a history of interactions between organisms
and conditions in their environments. The Empirical Strategy is termed “empirical” precisely for rooting the character of perceptions in past experience of the
individual or the species. How something is perceived, out of a spectrum of variant possibilities, is determined by how it has been acted upon – and not merely
on how it has been perceived – in the past. Past success in doing something in
response to a perception will act as a necessary condition in determining how the
object or scene in question is being perceived at present.
The authors commence from the “inverse optics problem”, also known as the
problem of the ambiguity of the retinal image, as it was paradigmatically formulated in Berkeley’s Essay Towards a New Theory of Vision (1709) and briefly
discussed earlier in this chapter. In view of this problem of perceptual ambiguity,
Berkeley’s proposal was to ground the ability to perceive distances and magnitudes of objects and, in fact, any spatial arrangement, in the perceiving subject’s
experience. Only from experiencing certain objects in certain constellations, one
learns to associate prima facie identical visual cues with different perceptual situations, and hence to reliably identify the correct distance, magnitude, and so forth
of objects.
Purves and his colleagues follow Berkeley’s lead when identifying the inverse
optics problem as the issue “that light stimuli cannot specify the objects and
conditions in the world that caused them” (Purves et al. 2011, 15588), and, like
Berkeley, they delegate the task of specification to the perceiving subject’s experience. Their solution to this problem, however, is not as exclusively based on
subjective experience as is Berkeley’s, and it certainly does not follow Berkeley’s
idealism. Instead, they adopt a more externalist and supra-individual stance. Conversely, with Gibsonian ecological psychology, the Empirical Strategists share
an emphasis on the relation between perception and environmentally embedded
behaviour and a markedly realist outlook.
The core of the Empirical Strategists’ argument can be parsed into three steps,
and it is this: “Proximal stimuli trigger patterns of neuronal activity that have been
shaped solely by the past consequences of visually guided behaviour” (Purves
et al. 2001, 285). These consequences, in turn, are evaluated purely in terms of
adaptive success rather than any correspondence with the measurable physical
properties of the perceived objects. Hence, the measurable physical properties
illusions, the normative qualities of my perceptual relation are determined by the
actual match or mismatch between the information that is present and the successful realisation of my abilities to act upon conditions in my environment, not
the illusionary appearances. Getting all the physical properties of an object right
might not be all that important in this respect (properties that Gibson did not care
much about either). This is the basic idea brought forward by one relatively recent
theory in cognitive psychology that has come to be known as the “Empirical Strategy” or, less memorably but more descriptively, the “wholly empirical approach
to perception” (Purves et al. 2001; Purves et al. 2011).
5
In combining an environment-directed outlook with a distinctive set of computational and statistical methods, the Empirical Strategy seeks to explain the peculiarities of perception by reference to a history of interactions between organisms
and conditions in their environments. The Empirical Strategy is termed “empirical” precisely for rooting the character of perceptions in past experience of the
individual or the species. How something is perceived, out of a spectrum of variant possibilities, is determined by how it has been acted upon – and not merely
on how it has been perceived – in the past. Past success in doing something in
response to a perception will act as a necessary condition in determining how the
object or scene in question is being perceived at present.
The authors commence from the “inverse optics problem”, also known as the
problem of the ambiguity of the retinal image, as it was paradigmatically formulated in Berkeley’s Essay Towards a New Theory of Vision (1709) and briefly
discussed earlier in this chapter. In view of this problem of perceptual ambiguity,
Berkeley’s proposal was to ground the ability to perceive distances and magnitudes of objects and, in fact, any spatial arrangement, in the perceiving subject’s
experience. Only from experiencing certain objects in certain constellations, one
learns to associate prima facie identical visual cues with different perceptual situations, and hence to reliably identify the correct distance, magnitude, and so forth
of objects.
Purves and his colleagues follow Berkeley’s lead when identifying the inverse
optics problem as the issue “that light stimuli cannot specify the objects and
conditions in the world that caused them” (Purves et al. 2011, 15588), and, like
Berkeley, they delegate the task of specification to the perceiving subject’s experience. Their solution to this problem, however, is not as exclusively based on
subjective experience as is Berkeley’s, and it certainly does not follow Berkeley’s
idealism. Instead, they adopt a more externalist and supra-individual stance. Conversely, with Gibsonian ecological psychology, the Empirical Strategists share
an emphasis on the relation between perception and environmentally embedded
behaviour and a markedly realist outlook.
The core of the Empirical Strategists’ argument can be parsed into three steps,
and it is this: “Proximal stimuli trigger patterns of neuronal activity that have been
shaped solely by the past consequences of visually guided behaviour” (Purves
et al. 2001, 285). These consequences, in turn, are evaluated purely in terms of
adaptive success rather than any correspondence with the measurable physical
properties of the perceived objects. Hence, the measurable physical properties