A scaling analysis of the snake lightness illusion

Logvinenko, Alexander D.; Petrini, Karin; Maloney, Laurence T.

doi:10.3758/pp.70.5.828

Cited by 22 publications

(26 citation statements)

References 37 publications

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“…In Experiment 1, we found that observers showed a degree of lightness constancy when the overall intensity of the scene illumination was varied. In contrast to the findings of Logvinenko and Maloney (2006; Logvinenko et al, 2008), however, our dissimilarity data are well-accounted for by a one-dimensional perceptual representation. In both Experiments 1 and 2, we found essentially no lightness constancy with respect to changing the slant of a test surface viewed under directional illumination – the dissimilarity data were well-accounted for by a one-dimensional perceptual representation and the positions of stimuli in this representation were a monotonic function of stimulus luminance across changes in slant.…”

Section: Discussioncontrasting

confidence: 99%

“…The scaling procedure yielded regular results that were consistent across subjects. In this regard, we agree with Logvinenko and Maloney (2006; Logvinenko et al, 2008) that the procedure provides a valuable addition to the set of available methods for studying lightness. Our scaling data revealed essentially no lightness constancy with respect to the slant manipulation, in distinction to our matching data and to many (e.g., Boyaci et al, 2003; Gilchrist, 1980; Hochberg & Beck, 1954; Lee & Brainard, 2014; Radonjić et al, 2010; Ripamonti et al, 2004) but not all (Epstein, 1961) previous studies of this phenomenon.…”

Section: Discussionsupporting

confidence: 84%

“…They interpreted this representation as one that provided perceptual correlates of both surface reflectance and of scene illumination. They also found that a two-dimensional representation was required to explain dissimilarity judgments in the context of a lightness illusion (Logvinenko, Petrini, & Maloney, 2008). …”

Section: Introductionmentioning

confidence: 99%

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Scaling Measurements of the Effect of Surface Slant on Perceived Lightness

Madigan

Brainard

2014

i-Perception

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The light reflected from an object depends on its reflectance, the illumination, and the pose of the object within the scene. An observer is called lightness constant if the perceived reflectance (lightness) of achromatic objects stays the same despite variation in object-extrinsic factors such as illumination and pose. Here, we used a dissimilarity scaling task to measure lightness constancy as the intensity of the illuminant and the slant of test surfaces were varied. Across two experiments, we had observers rate the dissimilarity of flat grayscale test stimulus pairs. The test stimuli were real illuminated surfaces, not computer simulations. Each test stimulus was seen in its own illuminated chamber, with the two chambers viewed side by side. We varied test surface reflectance, chamber illumination intensity, and the slant of the test in relation to the single light source in each chamber. Data were analyzed using nonmetric multidimensional scaling. The data were well-described by a one-dimensional perceptual representation. This representation was consistent across observers, revealed partial lightness constancy with respect to a change in illumination intensity, and no lightness constancy with respect to changes in surface slant. An additional experiment using a matching procedure and the same stimulus set, however, revealed moderate constancy with respect to changes in surface slant. The difference in results between the two methods is interesting, but not understood.

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Section: Discussioncontrasting

confidence: 99%

Section: Discussionsupporting

confidence: 84%

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Scaling Measurements of the Effect of Surface Slant on Perceived Lightness

Madigan

Brainard

2014

i-Perception

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“…Considerations of such stimuli inspired Logvinenko and his collaborators (Logvinenko & Maloney, 2006; Logvinenko, Petrini, & Maloney, 2008) to explore the dimensionality of perceptual experience via multidimensional scaling method. While this approach is novel and potentially fruitful it is not clear that it eliminates the potential for subjects to respond on the basis of explicit reasoning.…”

Section: Resultsmentioning

confidence: 99%

The nature of instructional effects in color constancy.

Radonjić¹,

Brainard²

2016

Journal of Experimental Psychology: Human Perception and Perfor

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The instructions subjects receive can have a large effect on experimentally measured color constancy, but the nature of these effects and how their existence should inform our understanding of color perception remains unclear. We used a factorial design to measure how instructional effects on constancy vary with experimental task and stimulus set. In each of two experiments, we employed both a classic adjustment-based asymmetric matching task and a novel color selection task. Four groups of naive subjects were instructed to make adjustments/selections based on 1) color (neutral instructions), 2) the light reaching the eye (physical spectrum instructions), 3) the actual surface reflectance of an object (objective reflectance instructions) or 4) the apparent surface reflectance of an object (apparent reflectance instructions). Across the two experiments we varied the naturalness of the stimuli. We find clear interactions between instructions, task and stimuli. With simplified stimuli (Experiment 1), instructional effects were large and the data revealed two instruction-dependent patterns. In one (neutral and physical spectrum instructions) constancy was low, inter-subject variability was also low, and adjustment-based and selection-based constancy were in agreement. In the other (reflectance instructions) constancy was high, inter-subject variability was large, adjustment-based constancy deviated from selection-based constancy and for some subjects selection-based constancy increased across sessions. Similar patterns held for naturalistic stimuli (Experiment 2), although instructional effects were smaller. We interpret these two patterns as signatures of distinct task strategies — one is perceptual, with judgments based primarily on the perceptual representation of color; the other involves explicit instruction-driven reasoning.

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“…It was found, for example, that the simultaneous lightness contrast illusion was rather strong for a pictorial wall of blocks (Adelson, 1993;Logvinenko, 1999), yet it either completely disappeared (Logvinenko, Kane, & Ross, 2002) or was considerably reduced (Logvinenko & Kane, 2003) when implemented as a real wall. Moreover, using the same multidimensional scaling technique as Logvinenko and Maloney (2006), Logvinenko, Petrini, and Maloney (2008) found that pictorial achromatic colours in the Adelson snakelike pattern made a one-dimensional manifold. In other words, no surface-brightness dimension was found, despite a clear pictorial impression of areas of different illuminations.…”

Section: Discussionmentioning

confidence: 99%

Lightness constancy and illumination discounting

Logvinenko

Tokunaga

2011

Atten Percept Psychophys

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Contrary to the implication of the term "lightness constancy", asymmetric lightness matching has never been found to be perfect unless the scene is highly articulated (i.e., contains a number of different reflectances). Also, lightness constancy has been found to vary for different observers, and an effect of instruction (lightness vs. brightness) has been reported. The elusiveness of lightness constancy presents a great challenge to visual science; we revisit these issues in the following experiment, which involved 44 observers in total. The stimuli consisted of a large sheet of black paper with a rectangular spotlight projected onto the lower half and 40 squares of various shades of grey printed on the upper half. The luminance ratio at the edge of the spotlight was 25, while that of the squares varied from 2 to 16. Three different instructions were given to observers: They were asked to find a square in the upper half that (i) looked as if it was made of the same paper as that on which the spotlight fell (lightness match), (ii) had the same luminance contrast as the spotlight edge (contrast match), or (iii) had the same brightness as the spotlight (brightness match). Observers made 10 matches of each of the three types. Great interindividual variability was found for all three types of matches. In particular, the individual Brunswik ratios were found to vary over a broad range (from .47 to .85). That is, lightness matches were found to be far from veridical. Contrast matches were also found to be inaccurate, being on average, underestimated by a factor of 3.4. Articulation was found to essentially affect not only lightness, but contrast and brightness matches as well. No difference was found between the lightness and luminance contrast matches. While the brightness matches significantly differed from the other matches, the difference was small. Furthermore, the brightness matches were found to be subject to the same interindividual variability and the same effect of articulation. This leads to the conclusion that inexperienced observers are unable to estimate both the brightness and the luminance contrast of the light reflected from real objects lit by real lights. None of our observers perceived illumination edges purely as illumination edges: A partial Gelb effect ("partial illumination discounting") always took place. The lightness inconstancy in our experiment resulted from this partial illumination discounting. We propose an account of our results based on the two-dimensionality of achromatic colour. We argue that large interindividual variations and the effect of articulation are caused by the large ambiguity of luminance ratios in the stimulus displays used in laboratory conditions.

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A scaling analysis of the snake lightness illusion

Cited by 22 publications

References 37 publications

Scaling Measurements of the Effect of Surface Slant on Perceived Lightness

Scaling Measurements of the Effect of Surface Slant on Perceived Lightness

The nature of instructional effects in color constancy.

Lightness constancy and illumination discounting

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