Word superiority in word detection

Observers searched for a single precued word or its nonword anagram under conditions of rapid serial visual presentation (RSVP). A word advantage was found over a wide range of presentation rates (32-160 msec/frame), under yes-no as well as forced choice conditions, and with both one or two input “channels.” These results suggest that word superiority in word detection occurs at a perceptual locus.     

Word and nonword superiority effects in a letter detection task

Subjects searched for predesignated consonant letters embedded in strings of consonants, consonants and vowels, or consonants and numbers. In Experiments 1-3, detection was quicker in the consonant-vowel and consonant-number strings than in the consonant strings. Apparently, vowels and numbers were less confusable distractors than are nontarget consonants. Experiment 4 tested whether psychophysical or categorical information about letters and numbers enabled subjects to process consonant-vowel and consonant-number strings more quickly. Results indicated that psychophysical characteristics of target and distractor letters mediated both word and nonword superiority effects.

     

Stimulus and response factors in mirror-image discrimination

Two choice-reaction time studies assessed the influence of stimulus-response mapping, stimulus complexity, and stimulus alignment on adults’ discrimination of mirror-image and nonmirror-image stimulus pairs. Half the subjects in Experiment 1 were instructed to treat nonmiiTor pairs as “same” and mirror pairs as “different”; the other half responded in the opposite manner. The first group responded more quickly to nonmirror pairs, while the second group responded more quickly to mirror pairs. This result, which held for horizontal stimuli (side by side) as well as for vertical stimuli (one above the other), confirms the importance of experiential factors in mirror-image “confusions. “ In Experiment 2. stimuli were drawn from a population of patterns whose complexity could be objectively defined. In general, the more complex the pattern, the slower the response and complexity seemed to influence the qualitative nature of pattern processing. In both experiments, subjects responded more quickly to horizontal stimuli than to vertical stimuli.     

Children read normal and reversed letters: A simple test of reading skill

Above- and below-average readers in grades 3, 5 and 7 named letters under two conditions. In one condition, letters were presented in normal orientation. In the other condition, letters were presented in left-right mirror image orientation. The ratio of (1) naming time on normal letters to (2) naming time on mirror image letters was calculated for each child. Good readers had lower ratios than poor readers. This was due primarily to the faster naming of normal letters by good readers. Good and poor readers named mirror image letters at similar speeds. Two possible explanations for the results are discussed. One explanation is that the skilled readers have a better memory for the normal orientation of the letter shapes. A second explanation is that skilled readers process more peripheral information, when naming, than their less skilled counterparts, but that this peripheral processing is curtailed when transformed text is presented.     

Alexia without agraphia: An experimental case study

A 51-year-old right-handed male experienced reading difficulty and an upper right visual field cut after a head injury. The patient's letter naming was impaired and word naming was painstakingly slow. Words were decoded in a letter by letter sequence and performance varied directly with word length. Apart from his reading difficulties the patient was linguistically competent. He was sensitive to manipulations of word frequency and orthographic regularity. He wrote spontaneously and could identify the written counterpart to a spoken word with relative ease. Computerized axial tomography revealed damage to the posterior temporal-parietal region of the left hemisphere.     

Visual detection of multi-letter patterns

This study addressed two basic questions about the detection of multi-letter patterns: (a) How is the detection of a multi-letter pattern related to the detection of its individual components? (b) How is the detection of a sequence of letters influenced by the observer's familiarity with that sequence? In three experiments observers searched for one-, two-, or three letter patterns embedded in a rapid series of multiple six-letter frames. In Experiment 1, unfamiliar two-letter patterns were detected more accurately than their one-letter components. This two-letter advantage reflects the fact that in an array of fixed size, larger target stimuli contain more information and are easier to discriminate from nontarget alternatives. Quantitative analyses indicated that observers combine information not decisions, about the component letters in a pattern. In Experiment 2, with statistical and physical properties equated, a familiar three-letter pattern (i.e., CAT) was detected more accurately than its unfamiliar anagram (i.e., TCA). This word advantage in word (not letter) detection persisted even after extensive practice and was uninfluenced by the lexical character of distractor items. In Experiment 3, words (e.g., FIB), pronounceable non words (e.g., FIF(, and familiar acronyms (e.g., FBI) were detected more readily than unfamiliar items (e.g., IBF). Thus both orthographic knowledge and familiarity with specific sequences can facilitate perceptual processing in "word" detection.     

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.     

Stimulus uncertainty does not impair stereopsis

The effect of stimulus uncertainty on the stereoscopic resolution of letters was examined for two classes of letters: (1) letters presented stereoscopically as random-element stereograms, and (2) letters presented as two-dimensional physical contours. The variables of stimulus discriminability (stereoscopic vs. physical contours) and stimulus uncertainty (number of alternative letter targets) were combined factorially. Stereoscopically presented letters were more difficult to resolve, but stimulus uncertainty had the same effect for both stereoscopic and physically defined letters. The additivity of these two variables suggests that the perception of stereoscopic forms is an automatic process not impaired by uncertainty about the form to be resolved.     

Perspective effects in nondeontic versions of the Wason selection task

Perspective effects in the Wason four-card selection task occur when people choose mutually exclusive sets of cards depending on the perspective they adopt when making their choice. Previous demonstrations of perspective effects have been limited to deontic contexts--that is, problem contexts that involve social duty, like permissions and obligations. In three experiments, we demonstrate perspective effects in nondeontic contexts, including a context much like the original one employed by Wason (1966, 1968). We suggest that perspective effects arise whenever the task uses a rule that can be interpreted biconditionally and different perspectives elicit different counterexamples that match the predicted choice sets. This view is consistent with domain-general theories but not with domain-specific theories of deontic reasoning--for example, pragmatic reasoning schemas and social contract theory--that cannot explain perspective effects in nondeontic contexts.