The psychophysics of iconic storage

Some simple models of iconic storage, based on the persisting responses of photoreceptors, were tested in two experiments. Substantial changes in such physical parameters as adapting luminance, stimulus luminance, and stimulus contrast produced little or no change in the duration of partial-report performance. This is at odds with most receptoral models. It seems unlikely that any model based on receptoral persistence can accommodate the results, thus forcing one to locate the icon beyond the receptors and probably beyond the retina as a whole.     

Mutual information, perceptual independence, and holistic face perception

The concept of perceptual independence is ubiquitous in psychology. It addresses the question of whether two (or more) dimensions are perceived independently. Several authors have proposed perceptual independence (or its lack thereof) as a viable measure of holistic face perception (Loftus, Oberg, & Dillon, Psychological Review 111:835–863, 2004; Wenger & Ingvalson, Learning, Memory, and Cognition 28:872–892, 2002). According to this notion, the processing of facial features occurs in an interactive manner. Here, I examine this idea from the perspective of two theories of perceptual independence: the multivariate uncertainty analysis (MUA; Garner & Morton, Definitions, models, and experimental paradigms. Psychological Bulletin 72:233–259, 1969), and the general recognition theory (GRT; Ashby & Townsend, Psychological Review 93:154–179, 1986). The goals of the study were to (1) introduce the MUA, (2) examine various possible relations between MUA and GRT using numerical simulations, and (3) apply the MUA to two consensual markers of holistic face perception^—recognition of facial features (Farah, Wilson, Drain, & Tanaka, Psychological Review 105:482–498, 1998) and the composite face effect (Young, Hellawell, & Hay, Perception 16:747–759, 1987). The results suggest that facial holism is generated by violations of several types of perceptual independence. They highlight the important theoretical role played by converging operations in the study of holistic face perception.     

On relations among perceptual and cognitive measures of information processing

Tests of visual information processing and verbal information processing were administered to 178 Ss. Intercorrelations showed low positive relationships between two sets of two cognitive measures each, the Sentence Completion Test (Schroder, Driver, & Streufert, 1967) and the Interpersonal Topical Inventory (Tuckman, 1965), and the Interpersonal Topical Inventory and the Polarity Scale (1965), and a high negative correlation between preference for highly complex and for moderately complex visual stimuli. Factor analysis showed three reliable major factors. There was little evidence for a relationship between perceptual and cognitive processing characteristics, which indicates some danger for general theorists.     

Read-out of emotional information from iconic memory: the longevity of threatening stimuli

Previous research has shown that emotional stimuli are more likely than neutral stimuli to be selected by attention, indicating that the processing of emotional information is prioritized. In this study, we examined whether the emotional significance of stimuli influences visual processing already at the level of transient storage of incoming information in iconic memory, before attentional selection takes place. We used a typical iconic memory task in which the delay of a poststimulus cue, indicating which of several visual stimuli has to be reported, was varied. Performance decreased rapidly with increasing cue delay, reflecting the fast decay of information stored in iconic memory. However, although neutral stimulus information and emotional stimulus information were initially equally likely to enter iconic memory, the subsequent decay of the initially stored information was slowed for threatening stimuli, a result indicating that fear-relevant information has prolonged availability for read-out from iconic memory. This finding provides the first evidence that emotional significance already facilitates stimulus processing at the stage of iconic memory.     

Processing of perceptual information is more robust than processing of conceptual information in preschool-age children: evidence from costs of switching

Is processing of conceptual information as robust as processing of perceptual information early in development? Existing empirical evidence is insufficient to answer this question. To examine this issue, 3- to 5-year-old children were presented with a flexible categorization task, in which target items (e.g., an open red umbrella) shared category membership with one test item (e.g., a folded umbrella) and perceptual characteristics with another test item (e.g., a red mushroom). Participants were instructed to either categorize stimuli by the same dimension (i.e., perceptual similarity or category membership) in both phases of the task, or switch from categorizing by one dimension to categorizing by the other dimension. Results pointed to a strong asymmetry in switch costs: conceptual switch costs were higher than perceptual switch costs. These results suggest that processing of perceptual information remains more robust than processing of conceptual information at least until 5 years of age.     

Visual detection and perceptual independence: Assessing color and form

Visual stimuli are multidimensional. One important perceptual problem is to determine how the dimensions are combined. One important aspect of dimensional combination is whether the dimensions are perceptually independent or perceptually correlated. A new task is presented—the visual detection task—that directly assesses the degree of perceptual correlation between any two dimensions. Two experiments were conducted that assess the degree of perceptual correlation between form and color during the early stages of perceptual analysis. The results show that form and color are not perceptually independent. In addition, the pattern of perceptual correlation found indicates that form and color are not processed independently. The pattern of results constrains all models of early vision. A model of early vision based on active signal modulation is proposed.     

Preferential processing of self-relevant stimuli occurs mainly at the perceptual and conscious stages of information processing

Self-related stimuli, such as one’s own name or face, are processed faster and more accurately than other types of stimuli. However, what remains unknown is at which stage of the information processing hierarchy this preferential processing occurs. Our first aim was to determine whether preferential self-processing involves mainly perceptual stages or also post-perceptual stages. We found that self-related priming was stronger than other-related priming only because of perceptual prime-target congruency. Our second aim was to dissociate the role of conscious and unconscious factors in preferential self-processing. To this end, we compared the “self” and “other” conditions in trials where primes were masked or unmasked. In two separate experiments, we found that self-related priming was stronger than other-related priming but only in the unmasked trials. Together, our results suggest that preferential access to the self-concept occurs mainly at the perceptual and conscious stages of the stimulus processing hierarchy.     

Individual differences in perceptual space for tactile textures: evidence from multidimensional scaling

Ratio scaling was used to obtain from 5 subjects estimates of the subjective dissimilarity between the members of all possible pairs of 17 tactile surfaces. The stimuli were a diverse array of everyday surfaces, such as corduroy, sandpaper, and synthetic fur. The results were analyzed using the multidimensional scaling (MDS) program ALSCAL. There was substantial, but not complete, agreement across subjects in the spatial arrangement of perceived textures. Scree plots and multivariate analysis suggested that, for some subjects, a two-dimensional space was the optimal MDS solution, whereas for other subjects, a three-dimensional space was indicated. Subsequent to their dissimilarity scaling, subjects rated each stimulus on each of five adjective scales. Consistent with earlier research, two of these (rough/smooth and soft/hard) were robustly related to the space for all subjects. A third scale, sticky/slippery, was more variably related to the dissimilarity data: regressed into three-dimensional MDS space, it was angled steeply into the third dimension only for subjects whose scree plots favored a nonplanar solution. We conclude that the sticky/slippery dimension is perceptually weighted less than the rough/smooth and soft/hard dimensions, materially contributing to the structure of perceptual space only in some individuals.     

Direct estimation of multidimensional perceptual distributions: assessing hue and form

The procedures developed to assess the perceptual and decisional processes associated with detection in multidimensional space all require specialized statistical skills and analysis programs. The present article describes a regression model, designed to assess dimensional interactions, that is both computationally simpler and more accessible than those procedures. The papervalidates the regression model by comparing the perceptual space associated with the detection of hue and form mapped by the regression model with that mapped by Kadlec and Townsend's (1992a, 1992b) macro- and microanalyses. The results of both analyses showed that hue strongly influences the perception of form but that form only weakly influences the perception of hue. The parallel results of the two analyses suggest that the regression model is a valid alternative to multidimensional signal detection theory analysis.     

Developmental changes in face processing: results from multidimensional scaling

Multidimensional scaling procedures were used to investigate developmental changes in the ability to process previously unfamiliar faces. Eighty male subjects, aged 7, 9, 12, or adult, rated the similarity of pairs of faces. The faces were presented to subjects in either the upright or the inverted orientation. Multidimensional scaling analyses suggest that subjects of all ages use similar information in judging the similarity of faces. However, for upright faces, individual subjects under age 10 seem to use fewer features at a time. The results argue against a qualitative shift in face processing at age 10, and suggest that the improvement in face recognition ability noted at this age is due at least in part to an increased ability to consider more features simultaneously.     

The prioritization of perceptual processing in categorization

In three experiments, the effects of selective attention on perceptual processes in a complex multidimensional object categorization task were investigated. In each experiment, participants completed a perceptual-matching task to gain estimates of the perceptual salience of each stimulus dimension, then a categorization task using the same stimuli. In Experiments 1 and 2, the perceptual processing of stimulus dimensions was faster when dimensions were more diagnostic of category membership, regardless of their perceptual salience. Experiment 3 demonstrated that this prioritization of perceptual processing was evident even when stimuli were presented in unpredictable locations during categorization, indicating that the physical characteristics of the stimulus guide selective attention to diagnostic stimulus dimensions.     

Structural stimulus complexity: one factor influencing the clarity of iconic storage

Using the procedure of partial report, or the probe technique, five Ss were required to process the position of items from a matrix containing fewer items than matrix cells. Different sets of stimulus cards containing items of varying structural complexity such as circles, 4-sided and 8-sided shapes were used to test the hypothesis that structural stimulus complexity and clarity of iconic storage are inversely related. Results were in accordance with the hypothesis and implications for the processing of visual information were discussed.     

Wholistic and analytic stimulus processing: The development of selective perceptual strategies

This experiment reports an investigation of the development of selective processing strategies as subjects become increasingly more practised at a serial self-paced RT task. It demonstrates the effect a preceding stimulus can have on the analysis of a current signal and the development of active analytic strategies in favour of passive wholistic processing, with practice. The stimuli used were letters with irrelevant visual noise dot patterns superimposed on them. The letter, or the dot pattern, or both, could be repeated on successive trials. Early in practice repetition of both stimulus components simultaneously produced short reponse latencies relative to repetition of the letter alone. The number of noise dots markedly affected RT. Late in practice, however, letter repetition RTs were small, irrespective of whether or not the noise dot pattern was repeated. Furthermore, the number of noise dots no longer had an effect on the RT to these stimulus transitions. The results suggest that subjects appear to be able to select relevant information to process as they become progressively more practised, even though there is evidence that they compare the current stimulus with an iconic representation of the immediately preceding one.     

Some functional properties of iconic storage in retarded and nonretarded subjects

Four experiments, which examine some functional properties of iconic storage in mildly retarded subjects, are reported. Experiments I and III demonstrated that retardates report about three items, or one item less than normal subjects, after a single brief tachistoscopic exposure and that this span of attention was independent of size of array. Both normal and retarded groups reported more items correctly when arrays were arranged on two lines. Experiment II determined that exposure durations up to 250 msec did not influence the number of items reported by either group. Experiment IV compared the form of decay for both groups by cuing report of each of seven positions at five poststimulus delays. The presence of the typical W-shaped curve for both groups at all delays permitted the inference that items in iconic storage decay together rather than individually. Although quantitative differences existed between groups, in no case did intelligence interact with the manipulated variables. The results were discussed in relation to control processes and structural features within an information processing model of memory.