Perceptual encoding in comparative judgments of race

Ss made comparative judgments along the black-white racial dimension using opposite response sets (“Which is blacker?” or “Which is whiter?”). Three classes of pictures were used: B (black),W (white), and M (racially mixed). I or the BM judgments. “Which is whiter?” took significantly longer. The MW and BW judgments showed no difference between response instructions. Analysis of the stimuli showed that skin tone was not the primary perceptual attribute used in racial encoding. The observation of a funnel effect in the judgment latencies is shown to be consistent with other research demonstrating the effect of response set in comparative judgments Further. the results support sociological observations about the cultural use of the linguistic labels “black” and “white”     

On the perception of a class of bilaterally symmetric forms

Two experiments were performed to determine the manner in which people perceive a class of bilaterally symmetric forms. In the first experiment, paired, comparison dissimilarity judgments and unidimensional single stimulus ratings were collected from the Ss. The second experiment involved the collecting of semantic differential and paired comparison dissimilarity judgments from two groups of Ss. The judgments and ratings from both experiments were compared to each other and to a set of objective measures of the forms by a series of multivariate statistical techniques. It was found that three primary attributes, orientation, convexity-concavity, and curvature, accounted for the perceptual reports, but the manner in which the attributes were used differed for different response procedures and for the same response on different occasions.     

Reliability and dimensionality of judgments of visually textured materials

We extended perceptual studies of the Brodatz set of textured materials. In the experiments, texture perception for different texture sets, viewing distances, or lighting intensities was examined. Subjects compared one pair of textures at a time. The main task was to rapidly rate all of the texture pairs on a number scale for their overall dissimilarities first and then for their dissimilarities according to six specified attributes (e.g., texture contrast). The implied dimensionality of perceptual texture space was usually at least four, rather than three. All six attributes proved to be useful predictors of overall dissimilarity, especially coarseness and regularity. The novel attribute texture lightness, an assessment of mean surface reflectance, was important when viewing conditions were wide-ranging. We were impressed by the general validity of texture judgments across subject, texture set, and comfortable viewing distances or lighting intensities. The attributes are nonorthogonal directions in four-dimensional perceptual space and are probably not narrow linear axes. In a supplementary experiment, we studied a completely different task: identifying textures from a distance. The dimensionality for this more refined task is similar to that for rating judgments, so our findings may have general application.     

Remembering and knowing: Two means of access to the personal past

The nature of recollective experience was examined in a recognition memory task. Subjects gave “remember” judgments to recognized items that were accompanied by conscious recollection and “know” judgments to items that were recognized on some other basis. Although a levels-of-processing effect (Experiment 1) and a picture-superiority effect (Experiment 2) were obtained for overall recognition, these effects occurred only for “remember” judgments, and were reversed for “know” judgments. In Experiment 3, targets and lures were either preceded by a masked repetition of their own presentation (thought to increase perceptual fluency) or of an unrelated word. The effect of perceptual fluency was obtained for overall recogrntion and “know” judgments but not for “remember” judgments. The data obtained for confidencejudgments using the same design (Experiment4) indicated that “remember”/”know” judgments are not made solely on the basis of confidence. These data support the two-factor theories of recognition memory by dissociating two forms of recognition, and shed light on the nature of conscious recollection.     

Differential effects of familiarity on judgments of sameness and difference

Ss indicated whether pairs of simultaneously presented objects were “same” or “different.” In Experiments 1, 2, and 3 the stimuli were pairs of letters, and familiarity was manipulated by showing the letters in either an upright or an upside-down orientation. In Experiments 4 and 5 the stimuli were pairs of trigrams, and familiarity was manipulated either by rotation or by selection according to rated meaningfulness. Analysis of reaction times indicated that familiar pairs were responded to more quickly than were unfamiliar pairs; however, this was true only for “same” judgments, not for “different” judgments. In addition, Experiment 3 indicated that familiarity influenced discrimination accuracy under conditions of tachistoscopic exposure. Finally, in Experiment 6 an effort was made to disentangle the effects of meaningfulness from the effects of pronounceability. The present results stand in contrast to previous research using perceptual comparison tasks, since the earlier work failed to indicate any effect of familiarity.     

The effects of speed and accuracy strategies in an information-reduction task

Developmental changes in the ability to make relational judgments of sound intensity were examined with 3-, 4-, and 5-year-old children. The hypothesis that correct judgments of “louder” precede correct judgments of “softer” was supported. The results were discussed with reference to the development of the understanding of logical relations as proposed by Piaget. The role of magnitude of perceptual information in the development of relational judgments also was discussed.     

A theoretical framework for testing the additive difference model for dissimilarities data: Representing gambles as multidimensional stimuli

Implicit within the acceptance of most multidimensional scaling models as accurate representations of an individual's cognitive structure for a set of complex stimuli, is the acceptance of the more general Additive Difference Model (ADM). A theoretical framework for testing the ordinal properties of the ADM for dissimilarities data is presented and is illustrated for a set of three-outcome gambles. Paired comparison dissimilarity judgments were obtained for two sets of gambles. Judgments from one set were first analyzed using the ALSCAL individual differences scaling model. Based on four highly interpretable dimensions derived from this analysis, a predicted set of dimensions were obtained for each subject for the second set of gambles. The ordinal properties of the ADM necessary for interdimensional additivity and intradimensional subtractivity were then tested for each subject's second set of data via a new computer-based algorithm, ADDIMOD. The tests indicated that the ADM was rejected. Although violations of the axioms were significantly less than what would be expected by chance, for only one subject was the model clearly supported. It is argued that while multidimensional scaling models may be useful as data reduction techniques, they do not reflect the perceptual processes used by individuals to form judgments of similarity. Implications for further study of multidimensional scaling models are offered and discussed.     

SDT analysis of binary decisions and sensory intensity ratings to noxious thermal stimuli

During three sessions, each of 24 Ss responded to noxious thermal stimuli, using the following judgments: binary decision, S responded “high” or “low”; sensory intensity rating, S rated his sensory experience along a thermal intensity continuum; and concurrent report, S’s binary decision was followed by an intensity rating. The binary-decision d’ was significantly higher than the rating d′, suggesting that Ss could not maintain multiple thermal criteria in a consistent fashion. The criteria for pain obtained with single and concurrent intensity rating judgments did not differ. These results suggest that the most efficacious and valid method for the study of experimental pain is to obtain concurrent responses, and to use binary decisions to compute d’ and sensory intensity ratings to locate S’s criterion for reporting pain.     

Multidimensional scaling of hierarchical sorting data applied to facial expressions

A new algorithm for multidimensional scaling analysis of sorting data and hierarchical-sorting data is tested by applying it to facial expressions of emotion. We construct maps in “facial expression space” for two sets of still photographs: the I-FEEL series (expressions displayed spontaneously by infants and young children), and a subset of the Lightfoot series (posed expressions, all from one actress). The analysis avoids potential artefacts by fitting a map directly to the subject's judgments, rather than transforming the data into a matrix of estimated dissimilarities as an intermediate step. The results for both stimulus sets display an improvement in the extent to which they agree with existing maps. Some points emerge about the limitations of sorting data and the need for caution when interpreting MDS configurations derived from them.     

Evidence for all-or-none preperceptual processing in perceptual set

“Set” is known to improve the accuracy of report of the stimulus attributes for which Ss are set to respond. The set may produce this effect by acting on either preperceptual or postperceptual processes, or both. To elucidate the manner by which set produces its effect, this paper explores the consequences of two assumptions concerning set (1) On any given trial, a S is either “set” or “not set”: (2) if “set” by the stimulus information. S’s perception of the stimulus actually improves, whereas, if “not set” by the stimulus reformation, the S’s report correctness is improved by an independent interaction of stimulus and set information on a response process. Evidence is provided for both these assumptions. In addition. It is argued that only set given before stimulation can affect a perceptual process.     

Similarity structure in visual speech perception and optical phonetic signals

A complete understanding of visual phonetic perception (lipreading) requires linking perceptual effects to physical stimulus properties. However, the talking face is a highly complex stimulus, affording innumerable possible physical measurements. In the search for isomorphism between stimulus properties and phoneticeffects, second-order isomorphism was examined between theperceptual similarities of video-recorded perceptually identified speech syllables and the physical similarities among the stimuli. Four talkers produced the stimulus syllables comprising 23 initial consonants followed by one of three vowels. Six normal-hearing participants identified the syllables in a visual-only condition. Perceptual stimulus dissimilarity was quantified using the Euclidean distances between stimuli in perceptual spaces obtained via multidimensional scaling. Physical stimulus dissimilarity was quantified using face points recorded in three dimensions by an optical motion capture system. The variance accounted for in the relationship between the perceptual and the physical dissimilarities was evaluated using both the raw dissimilarities and the weighted dissimilarities. With weighting and the full set of 3-D optical data, the variance accounted for ranged between 46% and 66% across talkers and between 49% and 64% across vowels. The robust second-order relationship between the sparse 3-D point representation of visible speech and the perceptual effects suggests that the 3-D point representation is a viable basis for controlled studies of first-order relationships between visual phonetic perception and physical stimulus attributes.     

Prevarication: Reasoning from false assumptions

This paper examines the strategies t~sed in solving prevaricative reasoning problems. The task consisted of a noncontradictory set of propositions followed by an assumption that introduced an inconsistency. Ss were required to restore consistency by assigning truth values to propositions. When reasoning from false assumptions, Ss exhibit a specific strategy in assigning truth values: If forced to choose between the truth of a generality (e.g., All As are Bs) and that of a particular fact (e.g., This Y is a Z), the Ss assign the generality TRUE and the fact FALSE. Affirmative generalities are assigned TRUE more often than are negative ones, and those expressing class inclusion are assigned TRUE more often than those expressing property assignment. The data show that the selection of a “path” through this hypothetical reasoning problem cannot be attributed to either the syntactic form or the preexperimental credibility of the propositions. A generality coding model was discussed in terms of strategies sho~ in prevaricative reasoning problems as well as in other inference tasks.     

Relating inter-individual differences in metacognitive performance on different perceptual tasks

Human behavior depends on the ability to effectively introspect about our performance. For simple perceptual decisions, this introspective or metacognitive ability varies substantially across individuals and is correlated with the structure of focal areas in prefrontal cortex. This raises the possibility that the ability to introspect about different perceptual decisions might be mediated by a common cognitive process. To test this hypothesis, we examined whether inter-individual differences in metacognitive ability were correlated across two different perceptual tasks where individuals made judgments about different and unrelated visual stimulus properties. We found that inter-individual differences were strongly correlated between the two tasks for metacognitive ability but not objective performance. Such stability of an individual’s metacognitive ability across different perceptual tasks indicates a general mechanism supporting metacognition independent of the specific task.     

Avoiding the dangers of averaging across subjects when using multidimensional scaling

Ashby, Maddox and Lee (Psychological Science, 5 (3) 144) argue that it can be inappropriate to fit multidimensional scaling (MDS) models to similarity or dissimilarity data that have been averaged across subjects. They demonstrate that the averaging process tends to make dissimilarity data more amenable to metric representations, and conduct a simulation study showing that noisy data generated using one distance metric, when averaged, may be better fit using a different distance metric. This paper argues that a Bayesian measure of MDS models has the potential to address these difficulties, because it takes into account data-fit, the number of dimensions used by an MDS representation, and the precision of the data. A method of analysis based on the Bayesian measure is demonstrated through two simulation studies with accompanying theoretical analysis. In the first study, it is shown that the Bayesian analysis rejects those MDS models showing better fit to averaged data using the incorrect distance metric, while accepting those that use the correct metric. In the second study, different groups of simulated ‘subjects’ are assumed to use different underlying configurations. In this case, the Bayesian analysis rejects MDS representations where a significant proportion of subjects use different configurations, or when their dissimilarity judgments contain significant amounts of noise. It is concluded that the Bayesian analysis provides a simple and principled means for systematically accepting and rejecting MDS models derived from averaged data.     

Bayesian contour integration

The process by which the human visual system parses an image into contours, surfaces, and objects—perceptual grouping—has proven difficult to capture in a rigorous and general theory. A natural candidate for such a theory is Bayesian probability theory, which provides optimal interpretations of data under conditions of uncertainty. But the fit of Bayesian theory to human grouping judgments has never been tested, in part because methods for expressing grouping hypotheses probabilistically have not been available. This paper presents such methods for the case ofcontour integration—that is, the aggregation of a sequence of visual items into a “virtual curve.” Two experiments are reported in which human subjects were asked to group ambiguous configurations of dots (in Experiment 1, a sequence of five dots could be judged to contain a “corner” or not; in Experiment 2, an arrangement of six dots could be judged to fall into two disjoint contours or one smooth contour). The Bayesian theory accounts extremely well for subjects’ judgments, explaining more than 75% of the variance in both tasks. The theory thus provides a far more quantitatively precise account of human contour integration than has been previously possible, allowing a very precise calculation of the subjective goodness of a virtual chain of dots. Because Bayesian theory is inferentially optimal, this finding suggests a “rational justification,” and hence possibly an evolutionary rationale, for some of the rules of perceptual grouping.     

Confidence ratings in speech perception research: Evaluation of an efficient technique for discrimination testing

Discriminability of voice onset time was determined for four naive Ss in order to evaluate the relative efficiency of a testing procedure which utilized confidence ratings along with the conventional oddity task. Ss rated their judgments on oddity trials as “very very sure,” “somewhat sure,” or “just guessing.” Each S’s discrimination scores were given weights according to his ratings, yielding functions that were compared with those computed using unweighted percent correct scores. The confidence-rating technique produced readily interpretable results with about one-third as many judgments as are needed when the conventional procedure is used. Possible problems with the interpretation of the functions and the generalizability of the technique are discussed.     

Nonmetric tests of ratio vs. subtractive theories of stimulus comparison

Theories of stimulus comparison were tested by examining ordinal properties of data obtained with six scaling tasks. Subjects judged simple “ratios” or “differences” of stimulus pairs constructed from a factorial design. In four additional tasks, the same judges also compared relations between pairs of stimulus pairs, judging “ratios of ratios,” “ratios of differences,” “differences of ratios,” and “differences of differences.” The data were consistent with a subtractive theory, which asserts that two stimuli are compared by subtraction, regardless of the task, but that judges can compare two stimulus differences by either a ratio or a difference. All six tasks could be related by the subtractive theory using a single set of scale values. Other simple theories, including the theory that “ratio” judgments can be represented by a ratio model, could not reproduce the six rank orders (of the six sets of data) using a single set of scale values.     

Switching attention between the ears to monitor tones Nigel Harvey

Alternating dichotic presentation of tones was compared with monaural presentation in two different perceptual tasks. When Ss were asked to detect higher frequency target tones in fists of six background tones, they missed less than 5%. However, when the presentation was fast (10/sec) and the tones alternated dichotically, Ss reported “hearing” only three or four tones. In two further experiments, Ss were asked to judge the number of tones or to report their spatial and temporal positions; these tasks were much less accurately performed, for the dichotic lists, than the target detection task. The differing effects of switching rate on these tasks are discussed in relation to the types of processing they require.     

Memory and display search in binary classification reaction time

Attention, Perception, & Psychophysics - Character classification tasks and “same” “different” judgments of letter strings were examined with reference to major...