Evidence of fixed capacity in visual object categorization

Can one perceive multiple object shapes at once? We tested two benchmark models of object shape perception under divided attention: an unlimited-capacity and a fixed-capacity model. Under unlimited-capacity models, shapes are analyzed independently and in parallel. Under fixed-capacity models, shapes are processed at a fixed rate (as in a serial model). To distinguish these models, we compared conditions in which observers were presented with simultaneous or sequential presentations of a fixed number of objects (The extended simultaneous-sequential method: Scharff, Palmer, & Moore, 2011a, 2011b). We used novel physical objects as stimuli, minimizing the role of semantic categorization in the task. Observers searched for a specific object among similar objects. We ensured that non-shape stimulus properties such as color and texture could not be used to complete the task. Unpredictable viewing angles were used to preclude image-matching strategies. The results rejected unlimited-capacity models for object shape perception and were consistent with the predictions of a fixed-capacity model. In contrast, a task that required observers to recognize 2-D shapes with predictable viewing angles yielded an unlimited capacity result. Further experiments ruled out alternative explanations for the capacity limit, leading us to conclude that there is a fixed-capacity limit on the ability to perceive 3-D object shapes.

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“…Any observed effects must be attributed to attentional capacity limitations. For similar experiments see Palmer (1994) and Scharff et al (2011a).…”

Section: Experiments 2: Identical Displays With Cueingmentioning

confidence: 82%

“…Our recent study addresses a closely related question but confounds semantic categorization with object shape perception (Scharff, Palmer, & Moore, 2011a). We tested object categorization under divided attention, using a search task in which observers searched for a particular kind of animal on each trial.…”

Section: Theories Of Attention and Object Recognitionmentioning

confidence: 99%

Divided attention limits perception of 3-D object shapes

2013

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“…In this paradigm, two items are briefly presented and masked, either sequentially or simultaneously (John Duncan, 1980; Hoffman, 1978; Shiffrin & Gardner, 1972). Comparing performance in the sequential and simultaneous condition allows one to infer whether or not multiple items can be consolidated in parallel (Scharff, Palmer, & Moore, 2011a, 2011b). In both conditions, the memory load is the same while the number of items that need to be concurrently consolidated differs.…”

Section: Introductionmentioning

confidence: 99%

The bandwidth of consolidation into visual short-term memory depends on the visual feature

2014

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We investigated the nature of the bandwidth limit in the consolidation of visual information into visual short-term memory. In the first two experiments, we examined whether previous results showing differential consolidation bandwidth for color and orientation resulted from methodological differences by testing the consolidation of color information with methods used in prior orientation experiments. We briefly presented two color patches with masks, either sequentially or simultaneously, followed by a location cue indicating the target. Participants identified the target color via button-press (Experiment 1) or by clicking a location on a color wheel (Experiment 2). Although these methods have previously demonstrated that two orientations are consolidated in a strictly serial fashion, here we found equivalent performance in the sequential and simultaneous conditions, suggesting that two colors can be consolidated in parallel. To investigate whether this difference resulted from different consolidation mechanisms or a common mechanism with different features consuming different amounts of bandwidth, Experiment 3 presented a color patch and an oriented grating either sequentially or simultaneously. We found a lower performance in the simultaneous than the sequential condition, with orientation showing a larger impairment than color. These results suggest that consolidation of both features share common mechanisms. However, it seems that color requires less information to be encoded than orientation. As a result two colors can be consolidated in parallel without exceeding the bandwidth limit, whereas two orientations or an orientation and a color exceed the bandwidth and appear to be consolidated serially.

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“…For instance, in our divided attention condition, the observer can stop as soon as either the auditory or the visual target is found. However, suppose processing can finish only when phonemic recognition occurs in both the auditory and visual modalities; in this case, observed RTs will be determined by the slower of the 2 Note that it is possible to design experiments using accuracy that are useful in the study of processing architecture (e.g., Scharff, Palmer, & Moore, 2011;Shiffrin & Gardner, 1972;Townsend, 1981).…”

Section: Parallel Channel Modelsmentioning

confidence: 99%

The McGurk effect: An investigation of attentional capacity employing response times

Altieri

Lentz

Townsend

et al. 2016

Atten Percept Psychophys

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This paper proposes a novel approach to assess audiovisual integration for both congruent and incongruent speech stimuli using reaction times (RT). The experiments are based on the McGurk effect, in which a listener is presented with incongruent audiovisual speech signals. A typical example involves the auditory consonant/b/combined with a visually articulated/g/, often yielding a perception of/d/. We quantify the amount of integration relative to the predictions of a parallel independent model as a function of attention and congruency between auditory and visual signals. We assessed RT distributions for congruent and incongruent auditory and visual signals in a within-subjects signal detection paradigm under conditions of divided versus focused attention. Results showed that listeners often received only minimal benefit from congruent auditory visual stimuli, even when such information could have improved performance. Incongruent stimuli adversely affected performance in divided and focused attention conditions. Our findings support a parallel model of auditory-visual integration with interactions between auditory and visual channels.Keywords Speech perception . Attention: Selective . Reaction time methodsWhat cognitive mechanisms underlie speech recognition when audition is supplemented with visual information? The modern era of research into how auditory and visual speech cues interact began with Sumby and Pollack's (1954) seminal experimental work on audiovisual (AV) enhancement: They showed that visual cues provided by a talker's lip-movements facilitate auditory recognition across a range of signal-to-noise ratios. However, Massaro (1987a) proved that this outcome did not necessarily demonstrate integration since a singlechannel model could theoretically predict the results.In a critical study two decades later, McGurk and Macdonald (1976) reported a dramatic perceptual integration phenomenon that resulted from the presentation of incongruent auditory-visual speech signals. In what became known as the "McGurk effect," presentation of the auditory consonant/ b/over a visually articulated/g/yielded a fused percept of/d/. Audiovisual fusions such as these occur when the perceptual system maps cues from conflicting signals onto a phonemic category distinct from either input signal.1 Thus, the McGurk effect is a prime candidate with which to probe the mechanisms underlying integration.Several studies of the McGurk effect have been carried out, with the majority using mean accuracy as the dependent variable. In these studies, performance in auditory and visualonly trials is compared to accuracy in audiovisual trials, usually via confusion matrices (e.g., Massaro, 1987aMassaro, , 1998Massaro, , 2004. These experimental designs and modeling efforts have shed considerable light on speech integration: Auditory and visual cues appear to interact in a multiplicative manner 1 This cannot be demonstrated conclusively without also measuring responses to the single modality presentations (cf. Massaro 1987a(cf. M...

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Evidence of fixed capacity in visual object categorization

Cited by 39 publications

References 24 publications

Divided attention limits perception of 3-D object shapes

Divided attention limits perception of 3-D object shapes

The bandwidth of consolidation into visual short-term memory depends on the visual feature

The McGurk effect: An investigation of attentional capacity employing response times

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