Chaz Firestone

“Top-Down” Effects Where None Should Be Found The El Greco Fallacy in Perception Research

A tidal wave of recent research purports to have discovered that higher-level states such as moods, action capabilities, and categorical knowledge can literally and directly affect how things look. Are these truly effects on perception, or might some instead reflect influences on judgment, memory, or response bias? Here, we exploited an infamous art-historical reasoning error (the so-called “El Greco fallacy”) to demonstrate that multiple alleged top-down effects (including effects of morality on lightness perception and effects of action capabilities on spatial perception) cannot truly be effects on perception. We suggest that this error may also contaminate several other varieties of top-down effects and that this discovery has implications for debates over the continuity (or lack thereof) of perception and cognition.

How "Paternalistic" Is Spatial Perception? Why Wearing a Heavy Backpack Doesn't— and Couldn't—Make Hills Look Steeper

A chief goal of perception is to help us navigate our environment. According to a rich and ambitious theory of spatial perception, the visual system achieves this goal not by aiming to accurately depict the external world, but instead by actively distorting the environment’s perceived spatial layout to bias action selection toward favorable outcomes. Scores of experimental results have supported this view—including, famously, a report that wearing a heavy backpack makes hills look steeper. This perspective portrays the visual system as unapologetically paternalistic: Backpacks make hills harder to climb, so vision steepens them to discourage ascent. The “paternalistic” theory of spatial perception has, understandably, attracted controversy; if true, it would radically revise our understanding of how and why we see. Here, this view is subjected to a kind and degree of scrutiny it has yet to face. After characterizing and motivating the case for paternalistic vision, I expose several unexplored defects in its theoretical framework, arguing that extant accounts of how and why spatial perception is ability-sensitive are deeply problematic and that perceptual phenomenology belies the view’s claims. The paternalistic account of spatial perception not only isn’t true—it couldn’t be true, even if its empirical findings were accepted at face value.

Can you experience ‘top-down’ effects on perception?: The case of race categories and perceived lightness

A recent surge of research has revived the notion that higher-level cognitive states such as beliefs, desires, and categorical knowledge can directly change what we see. The force of such claims, however, has been undercut by an absence of visually apparent demonstrations of the form so often appealed to in vision science: such effects may be revealed by statistical analyses of observers’ responses, but you cannot literally experience the alleged top-down effects yourself. A singular exception is an influential report that racial categorization alters the perceived lightness of faces, a claim that was bolstered by a striking visual demonstration that Black faces appear darker than White faces, even when matched for mean luminance. Here, we show that this visually compelling difference is explicable in terms of purely low-level factors. Observers who viewed heavily blurred versions of the original Black and White faces still judged the Black face to be darker and the White face to be lighter even when these observers could not perceive the races of the faces, and even when they explicitly judged the faces to be of the same race. We conclude that the best subjectively appreciable evidence for top-down influences on perception does not reflect a genuinely top-down effect after all: instead, such effects arise from more familiar (if subtle) bottom-up factors within visual processing.

“Please Tap the Shape, Anywhere You Like” Shape Skeletons in Human Vision Revealed by an Exceedingly Simple Measure

A major challenge for visual recognition is to describe shapes flexibly enough to allow generalization over different views. Computer vision models have championed a potential solution in medial-axis shape skeletons—hierarchically arranged geometric structures that are robust to deformations like bending and stretching. In the experiments reported here, we exploited an old, unheralded, and exceptionally simple paradigm to reveal the presence and nature of shape skeletons in human vision. When participants independently viewed a shape on a touch-sensitive tablet computer and simply tapped the shape anywhere they wished, the aggregated touches formed the shape’s medial-axis skeleton. This pattern held across several shape variations, demonstrating profound and predictable influences of even subtle border perturbations and amodally filled-in regions. This phenomenon reveals novel properties of shape representation and demonstrates (in an unusually direct way) how deep and otherwise-hidden visual processes can directly control simple behaviors, even while observers are completely unaware of their existence.

On the origin and status of the "El Greco fallacy".

The oddly elongated forms painted by the Spanish Renaissance artist El Greco are popularly but incorrectly attributed to astigmatism. The particular reason this explanation fails has long offered a deep lesson for perceptual psychology, even motivating recent research. However, the details and historical origins of this lesson—often called the “El Greco fallacy”— have been obscured over many retellings, leading to an incomplete and even inaccurate understanding of its provenance and status. This note corrects the record, which is richer, subtler, and more interesting than recent accounts would suggest.

Seeing and thinking: Foundational issues and empirical horizons

The spectacularly varied responses to our target article raised big-picture questions about the nature of seeing and thinking, nitty-gritty experimental design details, and everything in between. We grapple with these issues, including the ready falsifiability of our view, neuroscientific theories that allow everything but demand nothing, cases where seeing and thinking conflict, mental imagery, the free press, an El Greco fallacy fallacy, hallucinogenic drugs, blue bananas, subatomic particles, Boeing 787s, and the racial identities of geometric shapes.

'Moral Perception' Reflects Neither Morality Nor Perception.

Recently, Gantman and Van Bavel [1] introduced the notion of ‘moral perception’ – the claim that ‘perception is preferentially attuned to moral content’ (p. 631). This bold hypothesis aims to directly link vision science and social psychology, and promises exciting consequences for both fields. We explore here what it would take to demonstrate its existence. We suggest that moral perception does not exist, and that the evidence adduced in its favor fails to support it, in at least three ways.

When do ratings implicate perception versus judgment? The “overgeneralization test” for top-down effects

ABSTRACT When looking at an object—say, a banana—we can both directly perceive its visual qualities (e.g., its size) and also make higher-level judgments about its visual and non-visual properties (e.g., not only its size, but also its cost). Suppose you obtain a rating of a property such as size. Does that rating implicate seeing or merely higher-level judgment? The answer often matters a great deal -- e.g., determining whether such ratings imply “top-down” effects of cognition on perception. Too often, however, this distinction is ignored in empirical investigations of such effects. Here we suggest a simple test for when such ratings can be used to implicate perception: whenever the very same experiment “overgeneralizes” to an unambiguously non-perceptual factor, the results cannot be used to draw implications about perception, per se. As a case study, we investigate an empirical report alleging that conservatives perceive Barack Obama as darker skinned than liberals do. Two simple experiments show that the very same effects, measured via the same “representativeness” ratings, obtain with unambiguously non-perceptual and even silly factors (involving bright red horns vs. halos, rather than brightness differences). We suggest that this renders such methods unable to implicate visual processing and we recommend that “overgeneralization tests” of this type always be conducted in such contexts.

Seeing and Thinking in Studies of Embodied “Perception”

Recent work argues that “embodied perception” findings aren’t about perception after all. Schnall (2017, this issue) mounts a defense by using classics from the history of social psychology to explain away various empirical challenges centered on the role of task demands. We find this discussion refreshing for seriously considering and responding to one of the six “pitfalls” that we have suggested compromise this literature (for discussion of all six, see Firestone & Scholl, in press-a). But we also think this defense is deeply confused in both theory and practice and is bound to make things worse, not better. Here’s why.

Seeing structure: Shape skeletons modulate perceived similarity

An intrinsic part of seeing objects is seeing how similar or different they are relative to one another. This experience requires that objects be mentally represented in a common format over which such comparisons can be carried out. What is that representational format? Objects could be compared in terms of their superficial features (e.g., degree of pixel-by-pixel overlap), but a more intriguing possibility is that they are compared on the basis of a deeper structure. One especially promising candidate that has enjoyed success in the computer vision literature is the shape skeleton—a geometric transformation that represents objects according to their inferred underlying organization. Despite several hints that shape skeletons are computed in human vision, it remains unclear how much they actually matter for subsequent performance. Here, we explore the possibility that shape skeletons help mediate the ability to extract visual similarity. Observers completed a same/different task in which two shapes could vary either in their skeletal structure (without changing superficial features such as size, orientation, and internal angular separation) or in large surface-level ways (without changing overall skeletal organization). Discrimination was better for skeletally dissimilar shapes: observers had difficulty appreciating even surprisingly large differences when those differences did not reorganize the underlying skeletons. This pattern also generalized beyond line drawings to 3-D volumes whose skeletons were less readily inferable from the shapes’ visible contours. These results show how shape skeletons may influence the perception of similarity—and more generally, how they have important consequences for downstream visual processing.