Moon Illusion Research Articles

The Role of Size Contrast and Empty Space in the Explanation of the Moon Illusion

The Role of Size Contrast and Empty Space in the Explanation of the Moon Illusion

How Big Do Things Look?

The idea that we have direct and infallible knowledge of appearances is still deeply entrenched; and even scholars who reject this idea often still presume that our normal awareness of the shape and size of objects includes awareness of something like the shape and size of the image it projects onto the retina. I show here how these ideas are undermined by some new empirical evidence regarding these features, as well as by some observations concerning the phenomenology of size, the familiar moon illusion, and the persistence of illusions more generally. These considerations further suggest a path for dealing with the phenomenology of appearance more broadly.

Psychophysical study of the moon illusion in paintings and landscape photos

The moon illusion is a visual deception when people perceive the angular diameter of the Moon/Sun near the horizon larger than that of the one higher in the sky. Some theories have been proposed to explain this illusion, but not any is generally accepted. Although several psychophysical experiments have been performed to study different aspects of the moon illusion, their results have sometimes contradicted each other. Artists frequently display(ed) the Moon/Sun in their paintings. If the Moon/Sun appears near the horizon, its painted disc is often exaggeratedly large. How great is the magnitude of moon illusion of painters? How different are the size enlargements of depicted lunar/solar discs? To answer these questions, we measured these magnitudes on 100 paintings collected from the period of 1534–2017. In psychophysical experiments, we also investigated the moon illusion of 10 test persons who had to estimate the size of the lunar/solar disc on 100 paintings and 100 landscape photographs from which the Moon/Sun was retouched. Compared to the lunar/solar disc calculated from reference distances estimated by test persons in paintings, painters overestimated the Moon's size on average Q = 2.1 ± 1.6 times, while the Sun was painted Q = 1.8 ± 1.2 times larger than the real one, where Q = r painted / r real is the ratio of the radii of painted ( r painted ) and real ( r real ) Moons/Suns. In landscape photos, test persons overestimated the Moon's size Q = 1.6 ± 0.4 times and the Sun was assumed Q = 1.7 ± 0.5 times larger than in reality, where Q = r test / r real is the ratio of the radius r test estimated by the test persons and the real radius r real of Moons/Suns. The majority of the magnitude of moon illusion Q = 1.6, 1.7, 1.8, 2.1, 2.8, 2.9 measured by us are larger than the Q -values 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8 obtained in previous psychophysical experiments due to methodological differences.

The Moon illusion explained by the projective consciousness model

Models of consciousness should account for the phenomenology of subjective experience, including perceptual illusions. The Moon Illusion is a paradigmatic example that has yet to be accounted for. The Moon often appears larger near the perceptual horizon and smaller high in the sky, though the visual angle subtended is invariant. We show how this illusion can result from the optimization of a 3D projective geometrical frame through free energy minimization, following the principles of the Projective Consciousness Model. The model accounts for all documented modulations of the illusion without anomalies (e.g., the “size-distance paradox”), surpasses other theories in explanatory power, makes sense of inter- and intra-subjective variability vis-à-vis the illusion, and yields new quantitative and qualitative predictions. Empirical data from a virtual reality experiment support the predictions of the model. We also discuss how the model suggests explanations for other relevant illusions, concerning objects both at far and nearer distances, including the sky dome illusion, illusions of perceived size observed in the context of crowding experiments, and the Ames Room illusion.

The influence of sloping cloud in the visual field on the cognitive determinants of military pilots' behavior.

The study analyzed the effectiveness of military pilots' behavior under the influence of false horizon illusion - a false perception of the real horizon. It was assumed that visual illusion tends to cause spatial disorientation (SD). The question was asked which orientation of the sloping cloud (right/left) would have a bigger impact on SD. The effectiveness of the flight profile performance under the influence of visual illusion was analyzed in the context of the field dependence (FD), field independence (FI) or field intermediate dependence (FINT) of perception, the effectiveness of attention and operational memory. The study covered 66 pilots. A flight simulator was used as a measure of effectiveness in performing the flight profile in spatial disorientation conditions. The effectiveness of attention and working memory was diagnosed using 4 computer tasks. It was revealed that the right sloping cloud (compared to the left sloping cloud) had a greater impact on military pilots' behavior. The cognitive style distinguishes the accuracy of the flight profile performance from the inclined cloud pointing to the right. The comparisons showed significant differences between the FI and FD pilot groups. All the pilots demonstrated the right-sided asymmetry of the flight rate. While performing tasks on the simulator, the FI pilots were characterized by a more stable rate than the FINT pilots. A general conclusion is that the "correct falling cloud" had a greater impact on pilots' behavior. The presented results confirm the hypothesis that susceptibility to visual illusions is significantly increased in the pilots characterized by field dependence while the pilots with the FINT style of perception are characterized by a greater variability of the flight rate. Int J Occup Med Environ Health. 2019;32(5):653-62.

The Moon Illusion as (Partly) an Error in Apparent Visual Angle: A New Possibility.

An illusory exaggeration of the horizon moon’s visual angle (together with an apparently larger physical size) may account for its dramatic appearance.

Auditory Verbal Working Memory Load Effects on a Simulator-Induced Spatial Disorientation Event.

INTRODUCTION: Working memory is an essential executive function for flying an aircraft and its limitations may jeopardize flight safety. This function is particularly critical when pilots have to struggle with spatial disorientation (SD) cues. This research aimed to assess the combined effect of the auditory N-back task (NBT) and simulator-induced SD cues on pilots' flight performance.METHODS: Using an SD simulator, 39 male military pilots (control N = 20; age M = 31.6; SD = 8.22, experimental N = 19; age M = 26.9; SD = 8.67) were exposed to 12 flight sequences, where 6 contained an SD conflict-3 with vestibular illusions and 3 with visual illusions. Additionally, the pilots from the experimental group were asked to perform an auditory NBT involving sound stimuli (the sequential letter memory task) as they performed during oriented and disoriented flight conditions.RESULTS: Pilots' flight performance from the NBT group were significantly worse than the control group in the approach and landing profiles involving visual illusions (for both nonconflict and conflict flight), and in the profile involving the false horizon illusion (only for the conflict flight). No increase in a pilot's susceptibility to SD was observed with any other profiles.DISCUSSION: The current study provides support that pilots' cognitive workload can negatively impact flight performance. Pilots are not always aware of altered flight parameters, which may indicate that they have lost spatial orientation, mainly as a result of visual illusion. If problems occur in maintaining proper flight parameters, pilots should direct all available mental resources to regain their orientation and withdraw from any other parallel tasks.Lewkowicz R, Stróżak P, Bałaj B, Francuz P. Auditory verbal working memory load effects on a simulator-induced spatial disorientation event. Aerosp Med Hum Perform. 2019; 90(6):531-539.

The moon size illusion does not improve perceptual judgments.

Recent studies suggest that the accuracy of perceptual judgments can be influenced by the perceived illusory size of a stimulus, with judgments being more accurate for increased illusory size. This phenomenon seems consistent with recent neuroscientific findings that representations in early visual areas reflect the perceived (illusory) size of stimuli rather than the physical size. We further explored this idea with the moon illusion, in which the moon appears larger when it is close to the horizon and smaller when it is higher in the sky. Participants (n=230) adjusted the orientation of an image of the moon on a smartphone to match the perceived orientation of the moon in the sky. Contrary to previous studies that investigated accuracy and size illusions, we found slightly lower perceptual judgment accuracy when the moon appeared large (close to the horizon) compared to when it appeared small (high in the sky).

Selective Attention and Working Memory Under Spatial Disorientation in a Flight Simulator

ABSTRACTObjective: The aim of this study was to test the effects of visual and vestibular spatial disorientation on the cognitive performance of military aviators while they were piloting a flight simulator.Background: Spatial disorientation (SD), the inability to correctly determine the position and orientation of the aircraft in relation to the ground, poses a serious threat in aviation and can impair the cognitive performance of pilots while flying. More evidence is needed on the effects of visual and vestibular SD on cognition in flight simulators.Method: Pilots performed an auditory selective attention (duration discrimination) task (Experiment 1, N = 16) or an auditory working memory (N-back) task (Experiment 2, N = 16) while completing 6 different flight profiles in the disorientation and control conditions in the GYRO-IPT flight simulator. The flight scenarios included 3 visual illusions (false horizon, shape constancy, size constancy) and 3 vestibular illusions (somatogyral illusion, Coriolis effect, the leans).Results: In both experiments the cognitive performance (task accuracy) decreased for flight profiles with the leans illusion. Also, the flight performance (measured as the number of control reversal errors) was worse for the false horizon illusion and for the somatogyral illusion in both experiments.Conclusion: The results suggest that SD, particularly the vestibular illusion of the leans, can impair selective attention and working memory processes.

Perception of straightness and parallelism with minimal distance information.

The ability of human observers to judge the straightness and parallelism of extended lines has been a neglected topic of study since von Helmholtz's initial observations 150years ago. He showed that there were significant misperceptions of the straightness of extended lines seen in the peripheral visual field. The present study focused on the perception of extended lines (spanning 90° visual angle) that were directly fixated in the visual environment of a planetarium where there was only minimal information about the distance to the lines. Observers were asked to vary the curvature of 1 or more lines until they appeared to be straight and/or parallel, ignoring any perceived curvature in depth. When the horizon between the ground and the sky was visible, the results showed that observers' judgements of the straightness of a single line were significantly biased away from the veridical, great circle locations, and towards equal elevation settings. Similar biases can be seen in the jet trails of aircraft flying across the sky and in Rogers and Anstis's new moon illusion (Perception, 42(Abstract supplement) 18, 2013, 2016). The biasing effect of the horizon was much smaller when observers were asked to judge the straightness and parallelism of 2 or more extended lines. We interpret the results as showing that, in the absence of adequate distance information, observers tend to perceive the projected lines as lying on an approximately equidistant, hemispherical surface and that their judgements of straightness and parallelism are based on the perceived separation of the lines superimposed on that surface.

The Moon as a Tiny Bright Disc: Insights From Observations in the Planetarium.

Despite a relatively constant visual angle, the size of the moon appears very variable, mostly depending on elevation and context factors--the so-called moon illusion. As our perceptual experience of the size of the moon is clearly limited to the perceptual sphere of the sky, however, we do not know whether the typical perception of the moon at its zenith reflects a veridical interpretation of its visual angle of only 0.5 degrees. When testing the moon illusion in a large-scale planetarium, we observed two important things: (a) variation in perceptual size was no longer apparent, and (b) the moon looked very much smaller than in any viewing condition in the real sky--even when comparing it at its zenith. A closer inspection of the control console of the planetarium revealed that classic-analog as well as updated-digital planetariums use projections of the moon with strongly increased sizes to compensate for the loss of a natural view of the moon in the artificial dome of the sky.

The squint Moon and the witch ball

A witch ball is a reflecting sphere of glass. Looking into the disk that it subtends, the whole sky can be seen at one glance. This feature can be exploited to see and photograph the squint Moon illusion, in which the direction normal to the illuminated face of the Moon—its ‘attitude vector’—does not appear to point towards the Sun. The images of the Sun and Moon in the disk, the geodesic connecting them, the Moon’s attitude, and the squint angle (distinct from the tilt), can be calculated and simulated, for all celestial configurations and viewing inclinations. The Moon direction antipodal to the Sun, corresponding to full Moon, is a singularity of the attitude vector field, with index +1. The main features of the witch ball images also occur in other ways of imaging the squint Moon.

The new moon illusion and the role of perspective in the perception of straight and parallel lines

In the new moon illusion, the sun does not appear to be in a direction perpendicular to the boundary between the lit and dark sides of the moon, and aircraft jet trails appear to follow curved paths across the sky. In both cases, lines that are physically straight and parallel to the horizon appear to be curved. These observations prompted us to investigate the neglected question of how we are able to judge the straightness and parallelism of extended lines. To do this, we asked observers to judge the 2-D alignment of three artificial "stars" projected onto the dome of the Saint Petersburg Planetarium that varied in both their elevation and their separation in horizontal azimuth. The results showed that observers make substantial, systematic errors, biasing their judgments away from the veridical great-circle locations and toward equal-elevation settings. These findings further demonstrate that whenever information about the distance of extended lines or isolated points is insufficient, observers tend to assume equidistance, and as a consequence, their straightness judgments are biased toward the angular separation of straight and parallel lines.

The Moon Illusion and Size–Distance Scaling—Evidence for Shared Neural Patterns

A moon near to the horizon is perceived larger than a moon at the zenith, although--obviously--the moon does not change its size. In this study, the neural mechanisms underlying the "moon illusion" were investigated using a virtual 3-D environment and fMRI. Illusory perception of an increased moon size was associated with increased neural activity in ventral visual pathway areas including the lingual and fusiform gyri. The functional role of these areas was further explored in a second experiment. Left V3v was found to be involved in integrating retinal size and distance information, thus indicating that the brain regions that dynamically integrate retinal size and distance play a key role in generating the moon illusion.

Cognitive Determinants of Pilots’ Effectiveness Under a False Horizon Illusion

This study examined the influence of field dependence on susceptibility to the false horizon illusion. Additionally, it investigated how executive functions might mediate this susceptibility. Sixty-six military pilots performed an experimental task on the Hyperion flight simulator and a number of computerized tasks that assessed their working memory and attentional processes. All pilots succumbed to the false horizon illusion. A sloping cloud had the most impact on the flight profile accuracy in field-dependent pilots. Cognitive predictors of spatial disorientation were different for field-dependent, independent, and intermediate pilots.

Measuring the apparent size of the Moon with a digital camera

The Moon appears to be much larger closer to the horizon than when higher in the sky. This is called the ‘Moon illusion’ since the observed size of the Moon is not actually larger when the Moon is just above the horizon. This paper describes a technique for verifying that the observed size of the Moon is not larger on the horizon. The technique can be performed easily in a high-school teaching environment. Moreover, the technique demonstrates the surprising fact that the observed size of the Moon is actually smaller on the horizon due to atmospheric refraction. For the purposes of this paper, several images of the Moon were taken with it close to the horizon and close to the zenith. The images were processed using a free program called ImageJ. The Moon was found to be 5.73 ± 0.04% smaller in area on the horizon then at the zenith.

Oculomotor Effects in the Size-Distance Paradox and the Moon Illusion

Drawing on 2 concepts—the resting position of the eyes and a binocular geometry for perceived size, the moon illusion is explained as the consequence of different oculomotor adjustments caused by change in the direction of gaze contingent upon the viewing conditions of the moon. Hence, each particular moon will be viewed with a different vergence state which, in turn, yields a different amount of binocular disparity. The vergence state will determine the perceived size of an object whereas disparity will determine its perceived distance. It is further contended that the perceived size of the moon is based on a new binocular information source for size perception enabling the size of an object to be perceived even in the absence of egocentric distance information. Discussion focuses on the paradoxical aspect of the moon illusion and how the size-distance invariance hypothesis may have contributed to its effect.

An interaction between body orientation and gravity produces a novel illusion in visual distance perception

Does perceived distance depend on gravity? The moon illusion, in which the moon looks smaller when viewed overhead, suggests that it might, although so many factors are involved in this complex illusion. Prior research assessing perceived distance had blindfolded observers walk to a remembered location. However, this precludes altering an observer’s orientation relative to gravity. Here, a crossmodal comparison of a visual line and a standard-length tactile rod provided a novel means for assessing the perception of distance by exploiting size constancy — a shorter perceptual visual length (measured in rod lengths) corresponds to a shorter perceived distance from the observer. Experiments were conducted in a fully decorated room that was oriented at 90° with respect to gravity (the York University tumbled room) and in an identical normally oriented control room. Observers maintained an upright orientation with respect to the rooms. Observers judged the length of a variable visual line, projected with a laser and a pair of galvanometers, and varied by a QUEST procedure, relative to a fixed length tactile rod. The length of the visual line matched to the reference length was significantly longer — compatible with being perceived as further away — in the tumbled room than in the control room. A separate experiment failed to replicate this change in distance perception when the observer’s orientation relative to gravity was changed outside the tumbled room, suggesting that the effect is due to a conflict between visually- and gravitationally-defined reference frames.

Historical Epistemology or History of Epistemology? The Case of the Relation Between Perception and Judgment

This essay aims to sharpen debates on the pros and cons of historical epistemology, which is now understood as a novel approach to the study of knowledge, by comparing it with the history of epistemology as traditionally pursued by philosophers. The many versions of both approaches are not always easily discernable. Yet, a reasoned comparison of certain versions can and should be made. In the first section of this article, I argue that the most interesting difference involves neither the subject matter nor goal, but the methods used by the two approaches. In the second section, I ask which of the two approaches or methods is more promising given that both historical epistemologists and historians of epistemology claim to contribute to epistemology simpliciter. Using traditional problems concerning the epistemic role of perception, I argue that the historical epistemologies of Wartofsky and Daston and Galison fail to show that studying practices of perception is philosophically significant. Standard methods from the history of epistemology are more promising, as I show by means of reconstructing arguments in a debate about the relation between perception and judgment in psychological research on the famous moon illusion.

The Influence of Information Processing on A False Horizon Illusion and Pilots' Effectiveness

The Influence of Information Processing on A False Horizon Illusion and Pilots' Effectiveness