Visual and acoustic confusability a visual search task

Visual and acoustic confusability between a target item and background items was varied in a visual search task. Visual confusability was a highly significant source of difficulty while acoustic confusability had no effect. The results do not seem to be interpretable within a theory which assumes compulsory auditory encoding of visual information.     

A developmental study of visual search behavior

Children in second, fourth and sixth grades and college sophomores were compared on a visual search and scanning task under three experimental conditions. In Condition I, a single target letter was sought in a list of letters of low visual confusability. In Condition II, two target letters were sought but only one appeared in a given list. In Condition III, a single target letter was sought in a list of letters of high confusability. Search time decreased with age in all three tasks. Searching for two targets was no harder than searching for one. A highly confusable visual context increased search time at all age levels.     

A developmental study of visual search behavior

Children in second, fourth and sixth grades and college sophomores were compared on a visual search and scanning task under three experimental condilions. In Condition I, a single target letter was sought in a list of letters of low visual confusability. In Condition II, two target letters were sought but only one appeared in a given list. In Condition III, a single target letter was sought in a list of letters of high confusability. Search time decreased with age in all three tasks. Searching for two targets was no harder than searching for one. A highly confusable visual context increased search time at all age levels.     

An alternative for judging confusability of visual letters.

Numerical values for shared distinctive features were derived from Gibson's (1) feature analysis of the 26 uppercase alphabet letters. Due to the lack of agreement among the empirical matrices, it is proposed that this more general table is a useful and practical approach for judging confusability of visual letters for uppercase items. Reaction time data from a Posner-type of letter-matching task support the effectiveness of the table for judging visual confusability among uppercase letters.     

An attempt to simulate letter-by-letter dyslexia in normal readers

We attempted to simulate the main features of letter-by-letter (LBL) dyslexia in normal readers through stimulus degradation (i.e. contrast reduction and removal of high spatial frequencies). The results showed the word length and the letter confusability effects characteristic of LBL dyslexia. However, the interaction of letter confusability and N size (i.e. a facilitatory effect only for low confusability targets) previously observed in LBL dyslexics [Arguin, M., Fiset, S., & Bub, D. (2002). Sequential and parallel letter processing in letter-by-letter reading. Cognitive Neuropsychology, 19, 535-555; Arguin, M., & Bub, D. (2006). Parallel processing blocked by letter similarity in letter dyslexia: a replication. Cognitive Neuropsychology, 22, 589-602; Fiset, D., Arguin, M. & McCabe, E. (2005a). The breakdown of parallel letter processing in letter-by-letter dyslexia. Cognitive Neuropsychology, 22, 1-22] was not found. Our results suggest that the type of visual degradation employed here may only partially correspond to the visual deficit present in LBL dyslexia and that this degradation may have prevented the normal readers from accessing visual information available to LBL dyslexics when they use the compensatory strategy of serial letter processing.     

Eye movements of prereaders to pseudowords containing letters of high and low confusability

Children were required to make same-different judgments about matched and unmatched pseudoword pairs containing middle letters of either high confusability (e.g.. ZPR.W or low confusability (e.g., EROI). Differential eye-movement patterns were observed between matched and unmatched low-confusion pairs. This finding would be predicted from a features analysis of the visual characteristics of the letters of the pseudowords. Low-confusion pseudowords contain more different visual features than high-confusion pseudowords. Therefore, in making a matching judgment. low-confusion pairs should require more eye movements; however, detection of a mismatch should be facilitated due to the greater availability of distinctive features.     

Item recognition with automatized performance

A theory for automatized performance in item recognition tasks is outlined. Automation occurs during practice with consistent mappings of stimuli to responses. Automatized processing at stages of pattern recognition, binary coding, and response evocation is described in sufficient detail to provide a qualitative explanation for (a) extant data on transfer of training (where previous theories fail), ( b ) known effects of visual confusability and positive set size, and (c) null effect of negative set size (demonstrated in Experiment 1). The effects of visual confusability and positive set size are ascribed to the stage of pattern recognition; it is suggested that their joint effects on reaction times and error rates (measured in Experiment 2) be explained at a quantitative level by a parallel random walk recognition model.     

Hemispheric competence and perceptual confusability

Hemispheric competence in performing easy and difficult letter classification was examined in an exact replication of a previous experiment by Jonides (1979). The present experiment failed to confirm Jonides's finding of right visual field advantage in conditions of perceptual confusability and left visual field superiority when the stimuli were easily discriminable. The results showed a trend in the opposite direction, but no significant interaction. This divergence is discussed with respect to existing evidence and methodological procedures.     

Inverse discrimination time as a perceptual distance for alphabetic characters

Reaction times to discriminate lower‐case letters were collected in an experiment. The inverse discrimination times were used to build metrics on the space of letters. These metrics were found to be significantly correlated with various well‐known letter confusability measures, and a meaningful dimensional analysis of the alphabet was performed. This methodology is mathematically well founded, it requires fewer data than common methods, and it appears to be highly sensitive to visual similarity between letters, which allows visual letter features to be effectively analysed.     

Confusability and interference between members of parafoveal letter pairs

In each of three experiments, confusability between members of a parafoveally exposed pair of letters affected accuracy of identifying the peripheral, but not the central, letter. Confusability was determined from a confusion matrix developed for each subject. In Experiment 1, only one letter in each pair was identified on each exposure, and the position of pair members was varied over trials while the absolute position of the pair was held at a constant distance from fixation. In Experiment 2, both letters were identified on each exposure. In Experiment 3, the criterion letter was presented at a constant distance from fixation, and both letters were identified on each exposure. Since results in Experiment 3 were the same as in Experiments 1 and 2, the effect cannot be explained with reference to an interaction between confusability and acuity. The implications of the findings for various models of visual information processing are discussed.     

Short-term retention of pictures and words: evidence for dual coding systems.

The recall of picture and word triads was examined in three experiments that manipulated the type of distraction in a Brown-Peterson short-term retention task. In all three experiments recall of pictures was superior to words under auditory distraction conditions. Visual distraction produced high performance levels with both types of stimuli, whereas combined auditory and visual distraction significantly reduced picture recall without further affecting word recall. The results were interpreted in terms of the dual coding hypothesis and indicated that pictures are encoded into separate visual and acoustic processing systems while words are primarily acoustically encoded.     

Accuracy of judging time to arrival: effects of modality, trajectory, and gender

Observers' accuracy in using time-to-arrival (Ta) information was examined in 4 experiments. The issues included use of visual vs. acoustic Ta information, use of acoustic Ta information by blind Ss, use of Ta information controlling for velocity, and effects of angle of approach and arrival time on judgment accuracy. Visual information was used more efficiently than audiovisual and auditory information. Blind Ss used acoustical approach information as accurately as sighted Ss used visual information. Radial, oblique, and transverse orientations were used to examine effects of approach trajectory. Radial events were underestimated, whereas the more accurate transverse approach was likely to be overestimated. Oblique angle events yielded intermediate accuracies implying a spatiotemporal anisotropy. Women underestimated Ta more than did men. Possible reasons for Ss' judgment accuracy, including linear vs. nonlinear optical changes and relation to spatial skills and experience, were discussed.     

Some evidence for parallel comparisons in a letter recognition task

Subjects were asked to judge successively presented letter trigrams “same” or “different.” The different stimuli were divided into four groups; not confusable (NC), acoustically confusable (AC), visually confusable (VC), and both visually and acoustically confusable (VC & AC). Reaction times (RT) were lengthened only by the double confusability. It is argued that comparisons are normally made in both channels, so that confusability in a single channel has no effect since the alternative channel is unimpaired. RTs are only increased when both channels are slowed down. A further experiment confirms this interpretation. When the situation is manipulated so that only the visual channel is employed, the VC group shows the same increase as the VC & AC group.     

Generation of visual representations

The visual confusability of uppercase letters was manipulated in a successive same-different task to study the conditions under which visual generation from auditory inputs would occur and to investigate the figural specificity of the generated representations. Prior experiments have shown that visual confusions do occur when the initial stimulus is auditory and the second one is visual, which indicates that auditory stimuli can be encoded into visual forms. There has been some suggestion, however, that the generated visual code may have been too abstract to differentiate between the two cases in which letters can appear. In the present experiment, although the confusion effect was not eliminated when the subjects had no advance knowledge regarding the case in which the visual stimulus would appear, the marked confusion effect obtained when the visual stimulus was an uppercase letter was substantially attenuated when the letter appeared in lowercase. This was taken to indicate that the visual characteristics of a generated visual representation may be relatively specific. The results also suggested that subjects may wait until after the second stimulus is presented before they generate the visual representation of the initial auditory stimulus.     

Development of visual,name, and conceptual memory codes for pictures

In a recognition memory task, 4-, 8-, and 16-year-olds quickly decided whether or not probe pictures were identical to remembered study pictures. Conceptual and visual, but not acoustic, confusion were evidenced by the longer latencies when probes were visually or conceptually related to study items than when unrelated or rhyming. Visual confusion arose only when seven or fewer pictures intervened between study and probe items, and the kinds of visual similarity that produced confusion changed with age. Conceptual confusion resulted only at longer lags, and the same kinds of conceptual relationships produced confusion at all ages. These findings are discussed in terms of the development of visual and semantic encoding processes.     

Perceptual learning of spatiotemporal events: evidence from an unfamiliar modality

Perceptual learning was examined in two experiments in which subjects, originally unfamiliar with vibrotactile stimulation, were required to identify dynamic vibrotactile patterns with static visual patterns of the same two-dimensional shapes. In Experiment 1 we examined changes in performance with practice under a variety of vibrotactile spatial and temporal conditions. In Experiment 2 we investigated transfer of learning from one set of vibrotactile patterns to another different set. In neither experiment were subjects supplied with knowledge of results. Substantial perceptual learning (improvement in identification with practice) was observed in Experiment 1, although a minority of subjects did not exhibit improvement. Experiment 2 confirmed the general findings of Experiment 1 and also provided evidence of substantial positive transfer. In both experiments, multidimensional scaling of pattern confusion data revealed that practice (and improvement in identification) did not qualitatively change the relative confusability of patterns, suggesting that the (informative) structure of the patterns, irrespective of familiarity with a specific set of patterns, determined confusability. The findings are interpreted in terms of learning constructs offered by E. J. and J. J. Gibson. We conclude by considering the prospects that a connectionist mechanism can account for the observed perceptual learning.     

Modality effects and the structure of short-term verbal memory

The effects of auditory and visual presentation upon short-term retention of verbal stimuli are reviewed, and a model of the structure of short-term memory is presented. The main assumption of the model is that verbal information presented to the auditory and visual modalities is processed in separate streams that have different properties and capabilities. Auditory items are automatically encoded in both the A (acoustic) code, which, in the absence of subsequent input, can be maintained for some time without deliberate allocation of attention, and a P (phonological) code. Visual items are retained in both the P code and a visual code. Within the auditory stream, successive items are strongly associated; in contrast, in the visual modality, it is simultaneously presented items that are strongly associated. These assumptions about the structure of short-term verbal memory are shown to account for many of the observed effect of presentation modality.     

Mechanisms of attentional selection: temporally modulated priority tags

When a single abrupt onset appears in a multielement display, it captures attention. When multiple onset elements occur, they have conditional priority over no-onset elements such that a limited number of onsets can be serviced with high priority in visual search (Yantis & Johnson, 1990). We report three experiments in which we assess two possible mechanisms for attentional prioritization: a priority queue into which a fixed number of high-priority elements are placed for early servicing during search, and a mechanism that temporarily tags all high-priority elements for early servicing or more frequent sampling. We manipulated the visual quality or inter-letter confusability of the stimuli to prolong encoding and/or comparison operations; this manipulation led to a decrease in the estimated number of elements serviced with high priority. We conclude that a mechanism incorporating temporally decaying priority tags is implicated in servicing multiple abrupt onsets in visual search.     

Self-rated right–left confusability and performance on the Money Road-Map Test

This study assessed the relationship between self-rated right–left confusability and performance on the Money Road-Map Test (MRMT). Eighty-six undergraduate university students (44 women and 42 men) rated right–left subjective confusability using a questionnaire, and then completed the MRMT. Low- and high-confusability groups were determined using self-rated confusability scores. The high-confusability participants were less accurate and slower than the low-confusability participants in completing the MRMT. Self-confusability ratings significantly correlated with both accuracy scores and completion times on the MRMT. Although, women showed a significantly greater inclination than men to judge themselves as being more prone to confusion in right–left discrimination, the male advantage was not observed in terms of accuracy of response: there was a significant difference only in the completion time on the MRMT.     

Picture memory: recognizing added and deleted details

When people are presented simple and complex pictures and then tested in a same-changed recognition test with a simple or complex form of each, d' is greater for the simple than the complex picture (Pezdek & Chen, 1982). The results of three experiments confirm the robustness of this "asymmetric confusability effect" and test a model of the processes underlying this effect. According to the model, pictures are schematically encoded such that the memory representation of both simple and complex pictures is similar to the simple form of each. In Experiment 1, a sentence was presented that described the central schema in the picture prior to subjects' viewing each picture. This manipulation exaggerated the asymmetric confusability effect; schematic processing thus underlies the effect. Results of Experiment 2 refute the hypothesis that the effect results from subjects erroneously anticipating a recall test rather than a recognition test. Furthermore, although some of the nonschematic elaborative information in complex pictures is stored in memory, it is difficult to retrieve to verify that something is missing when complex presentation pictures are changed to simple test pictures (Experiment 3). Thus, although people are able to distinguish large sets of old pictures from new distractor pictures, their ability to detect missing elaborative visual details is more limited.