The role of background knowledge in speeded perceptual categorization

We examined the time-course of the influence of background knowledge on perceptual categorization by manipulating the meaningfulness of labels associated with categories and by manipulating the amount of time provided to subjects for making a categorization decision. Extending a paradigm originally reported by Wisniewski and Medin (1994) (Cog. Sci. 18 (1994) 221), subjects learned two categories of children's drawings that were given either meaningless labels (drawings by children from 'group 1' or 'group 2') or meaningful labels (drawings by 'creative' or 'non-creative' children); the meaningfulness of the label had a significant effect on how new drawings were classified. In addition, half of the subjects were provided unlimited time to respond, while the other half of the subjects were forced to respond quickly; speeded response conditions had a relatively large effect on categorization decisions by subjects given the meaningless labels but had relatively little effect on categorization decisions by subjects given the meaningful labels. These results suggest that some forms of background knowledge can show an influence at relatively early stages in the time-course of a categorization decision.     

Simple knowledge structures for perceptual classification expert systems

A new approach is described for the development and structure of perceptual knowledge-based systems. This systematic method for acquiring perceptual knowledge for use in knowledge-based systems and for representing perceptual knowledge within the systems has revealed that two broad classes of perceptual activity can each be characterized by a single logical operator. The number of rules necessary to accomplish particular perceptual tasks can also be estimated.     

Scepticism, perceptual knowledge, and doxastic responsibility

Arguments for scepticism about perceptual knowledge are often said to have intuitively plausible premises. In this discussion I question this view in relation to an argument from ignorance and argue that the supposed persuasiveness of the argument depends on debatable background assumptions about knowledge or justification. A reasonable response to scepticism has to show there is a plausible epistemological perspective that can make sense of our having perceptual knowledge. I present such a perspective. In order give a more satisfying response to scepticism, we need also to consider the standing of background beliefs. This is required since the recognitional abilities that enable us to have perceptual knowledge are informed by, or presuppose, a picture or conception of the world the correctness of which we have not ascertained. The question is how, in the face of this, to make sense of responsible belief-formation. In addressing this problem I make a suggestion about the standing of certain crucial beliefs linking appearances with membership of kinds.     

Wright contra McDowell on perceptual knowledge and scepticism

One of the key debates in contemporary epistemology is that between Crispin Wright and John McDowell on the topic of radical scepticism. Whereas both of them endorse a form of epistemic internalism, the very different internalist conceptions of perceptual knowledge that they offer lead them to draw radically different conclusions when it comes to the sceptical problem. The aim of this paper is to maintain that McDowell’s view, at least when suitably supplemented with further argumentation (argumentation that he may or may not agree with), can be shown to be a viable alternative to Wright’s anti-sceptical proposal, one that retains the driving motivation behind Wright’s proposal while avoiding one of its most fundamental problems. Wright’s wholesale rejection of the McDowellian anti-sceptical strategy is thus premature.     

The perceptual nature of audiovisual interactions for semantic knowledge in young and elderly adults

Audiovisual interactions for familiar objects are at the core of perception. The nature of these interactions depends on the amodal – sensory abstracted – or modal – sensory-dependent – approach of knowledge. According to these approaches, the interactions should be respectively semantic and indirect or perceptual and direct. This issue is therefore a central question to memory and perception, yet the nature of these interactions remains unexplored in young and elderly adults. We used a cross-modal priming paradigm combined with a visual masking procedure of half of the auditory primes. The data demonstrated similar results in the young and elderly adult groups. The mask interfered with the priming effect in the semantically congruent condition, whereas the mask facilitated the processing of the visual target in the semantically incongruent condition. These findings indicate that audiovisual interactions are perceptual, and support the grounded cognition theory.     

Acquisition of categorical color perception: a perceptual learning approach to the linguistic relativity hypothesis

Color perception can be categorical: Between-category discriminations are more accurate than equivalent within-category discriminations. The effects could be inherited, learned, or both. The authors provide evidence that supports the possibility of learned categorical perception (CP). Experiment 1 demonstrated that observers' color discrimination is flexible and improves through repeated practice. Experiment 2 demonstrated that category learning simulates effects of "natural" color categories on color discrimination. Experiment 3 investigated the time course of acquired CP. Experiment 4 found that CP effects are acquired through hue- and lightness-based category learning and obtained interesting data on the dimensional perception of color. The data are consistent with the possibility that language may shape color perception and suggest a plausible mechanism for the linguistic relativity hypothesis.     

Whole-word units are used before orthographic knowledge in perceptual development

A visual search task for target letters in multiletter displays was used to investigate information-processing differences between college students and presecond-grade children (mean age = 7 years, 4 months). The stimulus displays consisted of single words, pronounceable pseudowords, and unpronounceable nonwords varying in length from three to five letters. The mean response times for indicating whether or not a target letter occurred in the display increased with the number of display letters for both groups, although there were apparent differences between groups in the rate of search and type of search strategy used. Pre-second-grade children responded faster to word displays than to pseudoword and nonword displays, indicating that familiar letter strings could be processed faster than unfamiliar strings regardless of whether or not the latter were consistent with rules of English orthography. In contrast, college students processed words and pseudowords about equally well, and both resulted in faster responses than nonwords. As reading skills develop, children apparently come to process familiar words differently from other letter strings. Only after a significant sightword vocabulary is established do children seem to recognize the regularities of standard English orthography and make use of this knowledge to facilitate perceptual processes.     

The perceptual factor

A further study of the perceptual factor, previously isolated in a factor analysis of a battery of fifty-six tests, is made in a manner designed also to determine whether the same seven primaries would be found in a different population of subjects and with another battery of tests. The tests are described, and the results of the analysis are given in detail. Much attention is given to the matter of the orthogonality of primary factors and to their psychological meaningfulness.     

Prior knowledge does not facilitate the perceptual organization of dynamic random-dot patterns

Three classes of models for the origins of perceptual organization—linear independence, cognitive facilitation, and self-organization—were tested by evaluating the effects of stimulus unccrtainty and pattern coherence on the detection of coherent motion in dynamic random-dot patterns. Stimulus patterns consisted of two successive frames of randomly positioned dots in which motion was perceived when the dot positions in successive frames were correlated and displaced. The number of alternative directions axed locations of motion and the degree of coherences correlation) between the two successive frames were manipulated. The effects of stimulus uncertainty were less than predicted by cognitive facilitation models and were less than predicted by one linear independence model Ichoice theory), although similar to the predictions of another linear model (the Peterson, Birdsall, & Fox, 1954, approximation of the optimum Gaussian model). Small, but significant, tendencies toward self-organization rather than linear independence of perceived motion in neighboring locations were indicated by a nonlinear effect of coherence on detection accuracy and by the superior detectability of the direction as compared with the location of motion.     

The perceptual classification of speech

By employing new methods of analysis to the physical signal, a number of researchers have provided evidence which suggests that there may be invariant acoustic cues which serve to identify the presence of particular phonetic segments (e.g., Kewley-Port, 1980; Searle, Jacobson, & Rayment, 1979; Stevens & Blumstein, 1978. Whereas previous studies have focused upon the existence of invariant properties present in the physical stimulus, the present study examines the existence of any invariant information available in the psychological stimulus. For this purpose, subjects were asked to classify either a series of full-CV syllables ([bi], [bε], [bo], [??], [di], [d∈], [do], [??]) or one of two series of chirp stimuli consisting of information available in the first 30 meec of each syllable. The full-formant chirp stimuli consisted of the first 30 msec of each syllable, whereas the two-formant chirps were composed of the first 30 msec of only the second and third formants. The object of the present study was to determine whether or not there was sufficient information available in either the full- or two formant chirp series to allow subjects to group the stimuli into two classes corresponding to the identity of the initial consonant of the syllables (i.e., [b], or [d]). A series of classification tasks were used, ranging from a completely free sorting task to a perceptual learning task with experimenter-imposed classifications. The results suggest that there is information available in the full-formant chirps, but not in the two-formant chirps, which allows subjects to group the sounds into classes corresponding to the identity of the initial consonant sounds.     

The phenomenological directness of perceptual experience

When you have a perceptual experience of a given physical object that object seems to be immediately present to you in a way it never does when you consciously think about or imagine it. Many philosophers have claimed that naïve realism (the view that to perceive is to stand in a primitive relation of acquaintance to the world) can provide a satisfying account of this phenomenological directness of perceptual experience while the content view (the view that to perceive is to represent the world to be a certain way) cannot. I argue that this claim is false. Specifically, I maintain that the only acceptable naïve realist account of the relevant phenomenology is circular and that the content view can provide a similar account. In addition, I maintain that a certain specific variety of the content view provides a non-circular and thus more satisfactory account of this phenomenology. If so, then contrary to what is commonly assumed there are powerful phenomenological grounds for preferring the content view to naïve realism.     

The formation of linked perceptual classes

Multiple-exemplar training with stimuli in four domains induced two new fill-based (A1' and A2') and satellite-image-based (B1' and B2') perceptual classes. Conditional discriminations were established between the endpoints of the A1' and B1' classes as well as the A2' and B2' classes. The emergence of linked perceptual classes was evaluated by the performances occasioned by nine cross-class probes that contained fill variants as samples and satellite variants as comparisons, along with nine other cross-class probes that consisted of satellite variants as samples and fill variants as comparisons. The 18 probes were first presented serially and then concurrently. Class-consistent responding indicated the emergence of linked perceptual classes. Of the linked perceptual classes, 70% emerged during the initial serial test. An additional 20% of the linked perceptual classes emerged during the subsequently presented concurrent test block. Thus, linked perceptual classes emerged on an immediate or delayed basis. Linked perceptual classes, then, share structural and fuctional similarities with equivalence classes, generalized equivalence classes, cross-modal classes, and complex maturally occurring categories, and may clarify processes such as intersensory perception.