Acuity — Also known as spatial resolution-- is the ability to resolve elements of stimuli. Common measures in the case of vision are the extent to which the subject can distinguish one dot from two dots, detect a gap between two figures, determine whether a rotating figure is rotating clockwise rather than counter-clockwise, ascertain whether two line segments are co-linear, distinguish a dotted from a solid line or detect which side of a Landolt Square a gap is on.
Attention — WilliamJames (1890, p. 404) famously said attention “…is the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought. Focalization, concentration, of consciousness are of its essence. It implies withdrawal from some things in order to deal effectively with others.” Except for the exclusion of unconscious attention, most scientists would accept something like that characterization today. Spatial attention is attention directed to portion of environmental space and is distinct from attention to a thing or a property.
Content — See representational content.
Contrast — Contrast in an environmental layout is often defined as the average difference in luminance between light and dark areas. (Luminance is the amount of light reflected.) More specifically, it is the luminance difference between the lightest and darkest areas divided by the sum of those luminances. There are alternative ways of defining the notion but the differences won’t matter here.
Determinately different — For items to look determinately different in contrast, their contrast phenomenologies cannot be almost completely overlapping. I noted that this notion makes sense from a representationist perspective. I said that if one patch is represented as 10%-30% in contrast and another patch as 10.5%-30.5% the representationist would need a good reason to deny that the phenomenologies almost completely overlap. Given that representationism is committed to phenomenal precision and phenomenal overlap, it is legitimate to assume them in an argument against representationism.
Diaphanousness — G.E.Moore (1903) famously said “... the moment we try to fix our attention upon consciousness and to see what, distinctly, it is, it seems to vanish: it seems as if we had before us a mere emptiness. When we try to introspect the sensation of blue, all we can see is the blue; the other element is as if it were diaphanous ...”
Direct realism — The view that the phenomenal character of perceptual experience is grounded in direct awareness of objects and properties in the world.
Endogenous attention — Endogenous attention is voluntary—what people often mean by “paying attention”.
Exogenous attention — Exogenous spatial attention is attention that is attracted, automatically by a highly visible change. It is sometimes referred to as “transient” attention, whereas endogenous spatial attention is “sustained”. Exogenous spatial attention peaks by 120 ms after the cue, whereas endogenous spatial attention requires at least 300 ms to peak and has no known upper temporal limit.
Fixation — To fixate a thing or area of space is to point your eyes at it.
Fovea — The fovea is the high density center of the retina. Foveal vision is the only vision that can be 20/20. If you hold your hand at arm’s length, your foveal perception encompasses about double the width of your thumb.
Gabor patches — The fuzzy (actually sinusoidal) grids in Figure 1 — and other figures.
Grounding — Phenomenology is grounded in representational content just in case it is in virtue of the representational content of an experience that it has the phenomenology it has.
Identity formulation of representationism — What it is for an experience to have a certain phenomenal character is for it to have a certain representational content.
Landolt Square — See Figure 2.
Phenomenal precision principle — (one form) If two things look the same in peripheral vision but determinately different in foveal vision, then the phenomenal precision of foveal vision is narrower than that of peripheral vision.
Phenomenal precision — As with everything phenomenal, nothing like a definition is possible. The best you can do is use words to point to a phenomenon that the reader has to experience from the first person point of view. The experience of a color as red is less precise than the experience of a color as crimson. According to representationism, phenomenal precision is just the phenomenology of the precision of representational content. We experience a percept with representational content of 10%-20% as having more precision than we experience a percept with representational content 10%-30%. For a direct realist, phenomenal precision is just the precision of the properties we are directly aware of. We can be directly aware of properties with different precisions, for example, crimson, or alternatively red. Similarly we can be directly aware of a 10%-20% contrast property and also a 10%-30% contrast property and the difference constitutes a phenomenal precision difference.
Prothetic vs metathetic — Prothetic dimensions have a zero point and intrinsic directionality, whereas metathetic dimensions have neither.
Receptive field — In vision, the receptive field of a neuron is the area of space that a neuron responds to. In tactile perception the receptive field of a neuron is often gauged physiologically—the field of sensory receptors that feed to that neuron.
Representational content — Condition of veridicality. A simple percept consists of a representation of an environmental property and a singular element that picks out an individual item (Burge 2010). The representational content is satisfied when the referent of the singular element has the property represented by the property-representation.
Representational Precision — The precision of a representation is a matter of the intervalic range. For example, the precision of a representation of contrast of 10%-20% is narrower than a representation of 10%-30%. Precision in the sense used here is not a matter of indeterminacy of interval borders.
Spatial frequency — A measure of how closely spaced light and dark areas are. One could think of it with regard to the Gabor patches as a matter of stripe density.
Supervenience formulation of representationism — If phenomenology supervenes on representational content, there can be no difference in the phenomenology of perception without a difference in its representational content.
Veridicality — The veridicality of the most basic percept representations is a matter of the item referred to by the singular element having the property represented by the property representation.