DOCSLIB.ORG

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

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Moon Illusion and Size–Distance Scaling—Evidence for Shared Neural Patterns The Moon Illusion and Size–Distance Scaling—Evidence for Shared Neural Patterns Ralph Weidner1*, Thorsten Plewan1,2*, Qi Chen1, Axel Buchner3, Peter H. Weiss1,4, and Gereon R. Fink1,4 Abstract ■ A moon near to the horizon is perceived larger than a moon pathway areas including the lingual and fusiform gyri. The func- at the zenith, although—obviously—the moon does not change tional role of these areas was further explored in a second ex- its size. In this study, the neural mechanisms underlying the periment. Left V3v was found to be involved in integrating “moon illusion” were investigated using a virtual 3-D environ- retinal size and distance information, thus indicating that the ment and fMRI. Illusory perception of an increased moon size brain regions that dynamically integrate retinal size and distance was associated with increased neural activity in ventral visual play a key role in generating the moon illusion. ■ INTRODUCTION psia; Sperandio, Kaderali, Chouinard, Frey, & Goodale, Although the moon does not change its size, the moon 2013; Enright, 1989; Roscoe, 1989). near to the horizon is perceived as relatively larger com- One concept of size constancy scaling implies that the pared with when it is located at the zenith. This phenome- retinal image size and the estimated distance of an object non is called the “moon illusion” and is one of the oldest are conjointly considered, thereby enabling constant size visual illusions known (Ross & Plug, 2002). Despite exten- perception of objects at different distances (Kaufman & sive research, no consensus has been reached regarding Kaufman, 2000). With respect to the moon illusion, appar- the underlying perceptual and neural correlates (Ross & ent distance theories, for example, propose that “the per- Plug, 2002; Hershenson, 1989). ceived distance to the moon at the horizon is greater than Many researchers agree that the moon illusion is caused to the zenith moon” (Kaufman & Kaufman, 2000), and by mechanisms that otherwise allow an accurate percep- therefore, despite the constant retinal size, the horizontal tion of an objectʼs size, regardless of its distance (size moon generates a larger percept than the zenithal moon. constancy). However, there are different opinions on One of many problems with this interpretation is, how- how size scaling and size constancy are implemented in ever, that participants tend to report the horizontal moon the human visual system. as both larger and nearer (Hershenson, 1989), a phenome- For instance, Berkeley (1709/1948) suggested that size non commonly referred to as the size–distance paradox. scaling is achieved by taking into account learned proprio- A potential solution of this paradox is to postulate the ceptive and visual cues such as the angle of regard or aerial existence of different levels of distance representations in perspective. It has furthermore been proposed that con- the brain (i.e., registered distance and apparent distance). stant size representations are formed by taking into According to this view, size distance scaling is initially account the relative size of neighboring objects (Baird, based on one form of distance representation (e.g., regis- Wagner, & Fuld, 1990; McCready, 1986; Restle, 1970; Rock tered distance), which makes the moon appear larger. & Ebenholtz, 1959), texture gradients, and invariant prop- This larger appearance then reduces “apparent” distance, erties of the environment (Gibson, 1979; please see Ross which results in the moon appearing closer (Gogel & & Plug, 2002; Ross & Plug, 1998, for more elaborated Mertz, 1989; Rock & Kaufman, 1962). reviews). In addition, perceived size has been linked to Likewise, the neural mechanisms underlying the moon oculomotor processes such as accommodation (accommo- illusion are unclear. Different variants of apparent dis- dative micropsia) and convergence (convergence micro- tance theories consistently suggest that the moon illusion involves brain areas that integrate distance and retinal (angular) object size to generate size–distance invariant 1Research Centre Jülich, 2Leibniz Research Centre for Working object representations. Environment and Human Factors (IfADo), Dortmund, Germany, Thus far, investigating the “natural” moon illusion within 3Heinrich-Heine-Universität Düsseldorf, 4Cologne University an fMRI setting was hindered by the fact that the moon *These authors contributed equally to this work. cannot easily be transferred to an artificial environment. © 2014 Massachusetts Institute of Technology Journal of Cognitive Neuroscience 26:8, pp. 1871–1882 doi:10.1162/jocn_a_00590 For instance, binocular vision seems to play an important fMRI Measurement and Data Preprocessing role in enhancing the apparent size of the nearby horizon Functional imaging data were acquired by means of a 3-T moon (e.g., Enright, 1989). Presenting the moon illusion TRIO MRI system (Siemens, Erlangen, Germany) using on a standard 2-D computer screen may thus obscure T2*-weighted EPI sequence (repetition time = 2.2 sec, important aspects. Nowadays, however, visual stimulus echo time = 30 sec). In Experiment 1, 415 volumes were presentation devices such as magnetic resonance (MR)- acquired, and 605 volumes were obtained in Experiment 2. compatible goggle systems allow 3-D presentation even Each volume consisted of 36 axial slices, allowing for within an fMRI environment, thereby enabling a functional whole-brain coverage (3 mm thickness, distance factor investigation of the moon illusion, albeit an artificial one. 10%, field of view 200 mm, 64 × 64 matrix, in-plane voxel The goal of this study was not only to reveal the neural size 3 × 3 mm2). correlates associated with experiencing this illusion by The fMRI data preprocessing and statistical inference transferring the moon illusion into an fMRI suitable set- were performed using the Statistical Parametric Mapping ting but also to relate the neural correlates underlying the software (Friston et al., 1994). The first four images were moon illusion to those linked to different levels of object excluded from the analysis, as these were acquired within size perception. the time period the MR signal needs to reach a steady To identify the neural network underlying the moon state. Images were spatially realigned to the fifth volume illusion and to delineate different levels of visual pro- to correct for interscan movement. Then the mean EPI cessing represented within such a network, two fMRI image for each participant was computed and spatially experiments were performed: The first experiment di- normalized to the Montreal Neurological Institute (MNI) rectly investigated the neural activity related to the moon template using the “unified segmentation” function in illusion by presenting computer-generated (binocular) SPM5 (Ashburner & Friston, 2005). The data were then 3-D stimuli of a virtual moon at two different positions smoothed using a Gaussian kernel of 8 mm FWHM. (low or high), either within a natural scene or on a neu- tral background resulting in a two factorial design (see Figure 1A). Brain regions underlying the moon illusion EXPERIMENT 1: MOON ILLUSION were expected to be revealed by an interaction between the factors moon position (low vs. high) and scene (with Stimuli or without). More specifically, the perceived size of the Visual stimuli were presented using an MR-compatible virtual moon was expected to be increased only at the 3-D goggle system (VisuaStim, Resonance Technology, lower position in combination with the presence of a Northridge, CA). The device consists of two thin-film tran- scene. sistor (TFT) displays with a screen diagonal of 37.5° visual A second experiment was performed to test whether angle. The stimuli that covered the whole display were the moon illusion is generated by brain regions that form presented as disparate images on the two TFT displays of size-invariant (linear) object representations by taking the binocular goggles and hence generated a marked into account retinal (angular) size and perceived distance. depth impression. The stimulus background consisted Such brain regions were identified by means of fMRI of either an artificial scene (henceforth “with scene”)or adaptation (Grill-Spector & Malach, 2001). Participants alternatively of a plain blue screen (henceforth “without saw spheres located in different depth planes, with either scene”; see Figure 1A). Orthogonal to the scene variable, constant or variable perceived size (see Figure 1B). The a small moon (0.83° visual angle) appeared at one of the latter was realized by altering the perceived distance be- two possible positions (low or high). Hence, the experi- tween observer and object while simultaneously keeping ment was based on a 2 × 2 factorial design with Scene the objectʼs retinal (angular) size constant. (with vs. without) and Moon Position (low vs. high) as within-subject variables. A behavioral pilot experiment (data not shown) had confirmed that this setting is appro- METHODS priate for reliably inducing the moon illusion. Throughout this fMRI experiment, two white bars were Participants presented continuously on the left and on the right margin Twenty-five healthy participants (12 women) participated of the screen, which served as background for a compari- in a single fMRI session consisting of two separate experi- son disk that was superimposed either on the left or on ments. All participants were paid for their participation the right bar. Its vertical position was set between the and gave informed consent before the
Load more

Recommended publications
  • PREDICTIVE PROCESSING in the RETINA THROUGH EVALUATION of the OMITTED-STIMULUS RESPONSE by SAMANTHA I. FRADKIN a Thesis to Be Su
    PREDICTIVE PROCESSING IN THE RETINA THROUGH EVALUATION OF THE OMITTED-STIMULUS RESPONSE By SAMANTHA I. FRADKIN A thesis to be submitted to the Graduate School-New Brunswick Rutgers, The State University of New Jersey In partial fulfillment of the requirements For the degree of Master of Science Graduate Program in Psychology Written under the direction of Steven M. Silverstein And approved by ______________________________________________ ______________________________________________ ______________________________________________ New Brunswick, New Jersey October 2020 ABSTRACT OF THE THESIS Predictive Processing in the Retina Through Evaluation of the Omitted-Stimulus Response By SAMANTHA I. FRADKIN Thesis Director: Dr. Steven M. Silverstein While previous studies have demonstrated that individuals with schizophrenia demonstrate predictive coding abnormalities in high-level vision, it is unclear whether impairments exist in low-level predictive processing within the disorder. Evaluation of the omitted-stimulus response (OSR), i.e., activity following the omission of a light flash subsequent to a repetitive stimulus, has been examined previously to assess prediction within retinal activity. Given that little research has focused on the OSR in humans, the present study investigated if predictive processing could be detected at the retinal level within a healthy human sample, and whether this activity was associated with high-level predictive processing. Flash electroretinography (fERG) was recorded while eighteen healthy control participants viewed a series of consecutive light flashes within a 1.96 Hz single-flash condition with a flash luminance of 85 Td · s, as well as a 28.3 Hz flicker condition with a flash luminance of 16 Td · s. Participants also completed the Ebbinghaus ii task, a context sensitivity task that assesses high-level predictive processing, and the Audio-Visual Abnormalities Questionnaire (AVAQ), which measures frequency of self- reported auditory and visual sensory distortions.
    [Show full text]
  • Vision Science and Psychology Approach to Adaptation Processes Lied in Base of Visual Illusions
    1st Annual International Interdisciplinary Conference, AIIC 2013, 24-26 April, Azores, Portugal - Proceedings- VISION SCIENCE AND PSYCHOLOGY APPROACH TO ADAPTATION PROCESSES LIED IN BASE OF VISUAL ILLUSIONS Prof. Maris Ozolinsh Mag. Didzis Lauva Olga Danilenko University of Latvia, Riga, Latvia Abstract: We have experimentally studied visual adaptation processes and compared results in various visual perception tasks. Adaptation stimuli were demonstrated on computer screen and differed each from other by their luminance, colour, duration and dynamics related to the excited retinal and consequently the cortex neural cells and corresponding visual areas. Depth and characteristic times of adaptation processes depend on visual perception task. The slowest characteristic times (in range up to 10 sec and more) from studied processes are for adaptation to size of moving targets exciting retinal cells by equiluminant and isochrome stimuli, that are processed along parvocellular and magnocellular visual pathways. We assume that neural cell physiology lays on the base of this kind of size adaptation. Another kind of size adaptation where retinal cell excitation is static realizes in Ebbinghaus illusion. Here parallel to ongoing adaptation process brain uses also previously acquired knowledge to make shift in decision about stimuli size, and physiological effects dominate over psychological effects in perception of such stimuli. Over- or underestimating sizes in Ebbinghaus illusion with non-moving stimuli realizes much faster, and the degree of perception errors practically does not depend whether margnocellular or parvocellular visual pathway are activated – contrary to adaptation to dynamic moving targets. Key Words: Perceptive fields, visual illusions, magnocellular, parvocellurar pathways, processing of colour signals Introduction: Human brain processes inputs from our senses in very smart manner including modifications of deduction according to feedbacks in the sense pathways or to our previous experience.
    [Show full text]
  • Visual Context Processing in Schizophrenia
    Empirical Article Clinical Psychological Science 1(1) 5 –15 Visual Context Processing in Schizophrenia © The Author(s) 2013 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/2167702612464618 http://cpx.sagepub.com Eunice Yang1,2, Duje Tadin3,4, Davis M. Glasser3, Sang Wook Hong1,5, Randolph Blake1,2, and Sohee Park1 1Department of Psychology, Vanderbilt University; 2Department of Brain and Cognitive Sciences, Seoul National University, Republic of Korea; 3Center for Visual Science and Department of Brain and Cognitive Sciences, University of Rochester; 4Department of Ophthalmology, University of Rochester; and 5Department of Psychology, Florida Atlantic University Abstract Abnormal perceptual experiences are central to schizophrenia, but the nature of these anomalies remains undetermined. We investigated contextual processing abnormalities across a comprehensive set of visual tasks. For perception of luminance, size, contrast, orientation, and motion, we quantified the degree to which the surrounding visual context altered a center stimulus’s appearance. Healthy participants showed robust contextual effects across all tasks, as evidenced by pronounced misperceptions of center stimuli. Schizophrenia patients exhibited intact contextual modulations of luminance and size but showed weakened contextual modulations of contrast, performing more accurately than controls. Strong motion and orientation context effects correlated with worse symptoms and social functioning. Importantly, the overall strength of contextual
    [Show full text]
  • The Final Publication Is Available at Pms.Sagepub.Com
    1 The final publication is available at pms.sagepub.com http://pms.sagepub.com/content/122/1/88.full.pdf Sherman JA, and Chouinard PA (2016) Attractive contours of the Ebbinghaus illusion. Perceptual and Motor Skills 122: 88–95. Title: Attractive contours of the Ebbinghaus illusion. Joshua A. Sherman School of Psychology and Public Health, La Trobe University, Victoria, Australia. E: [email protected] Philippe A. Chouinard * School of Psychology and Public Health, La Trobe University, Victoria, Australia. E: [email protected] Running Head: Contours and Ebbinghaus Illusion Keywords: Size perception, Ebbinghaus illusion, biphasic contour interaction theory. * Corresponding author. Summary: There is debate as to whether or not the Ebbinghaus illusion is driven by high-level cognitive size contrast mechanisms as opposed to low-level biphasic contour interactions. In this study, we examine the variability in effects that are shared between this illusion and a different illusion that cannot be explained logically by a size contrast account. This comparison revealed that nearly one quarter of the variability for one illusion is shared with the other – demonstrating how a size-contrast account cannot be the sole explanation for the Ebbinghaus illusion. 2 Introduction What processes occur along the progression from retinal input to an illusory perceptual experience of the Ebbinghaus illusion? The display causing the illusion consists of an inner circle surrounded by a ring of contextual circles that are physically either larger or smaller than the inner circle. The surrounding contextual elements leads the viewer to perceive the inner circle to appear smaller or larger than it actually is (Fig.
    [Show full text]
  • A Neuro-Mathematical Model for Size and Context Related Illusions
    A neuro-mathematical model for size and context related illusions. B. Franceschiello, A. Sarti, G. Citti March 2019 Abstract We provide here a mathematical model of size/context illusions, inspired by the functional architecture of the visual cortex. We first recall previous models of scale and orientation, in particular [46], and simplify it, only considering the feature of scale. Then we recall the deformation model of illusion, introduced by [16] to describe orientation related GOIs, and adapt it to size illusion. We finally apply the model to the Ebbinghaus and Delboeuf illusions, validating the results by comparing with experimental data from [34] and [44]. 1 Introduction Geometrical-optical illusions (GOIs) are a class of phenomena first discovered by German physicists and physiologists in the late XIX century, among them Oppel and Hering ([39], [22]), and can be defined as situations where a perceptual mismatch between the visual stimulus and its geometrical properties arise [53]. Those illusions are typically analyzed according to the main geometrical features of the stimulus, whether it is contours orientation, contrast, context influence, size or a combination of the above mentioned ones ([53, 38, 11]). arXiv:1908.10162v1 [q-bio.NC] 27 Aug 2019 Figure 1: The Ebbinghaus illusion (left) and the Delboeuf illusion (right) In this work we are mainly interested in size and context related phenomena, a class of stimuli where the size of the surroundings elements induces a misperception of the central target width. In figure 1, two famous effects are presented, the Ebbinghaus and Delboeuf illusions: the presence of circular inducers (figure 1, left) and of an annulus (figure 1, right) varies the perceived sizes of the central targets.
    [Show full text]
  • The Simplest Method to Measure the Geocentric Lunar Distance: a Case of Citizen Science
    The simplest method to measure the geocentric lunar distance: a case of citizen science Jorge I. Zuluaga1,a, Juan C. Figueroa2,b and Ignacio Ferrin1,c 1 FACom - Instituto de Física - FCEN, Universidad de Antioquia, Calle 70 No. 52-21, Medellín, Colombia 2 Independent Software Developer ABSTRACT We present the results of measuring the geocentric lunar distance using what we propose is the simplest method to achieve a precise result. Although lunar distance has been systematically measured to a precision of few millimeters using powerful lasers and retroreflectors installed on the moon by the Apollo missions, the method devised and applied here can be readily used by nonscientist citizens (e.g. amateur astronomers or students) and it requires only a good digital camera. After launching a citizen science project called the “Aristarchus Campaign”, intended to involve astronomy enthusiasts in scientific measurement of the Lunar Eclipse of 15 April 2014, we compiled and measured a series of pictures obtained by one of us (J.C. Figueroa). These measurements allowed us to estimate the lunar distance to a precision of ~3%. We describe here how to perform the measurements and the method to calculate from them the geocentric lunar distance using only the pictures time stamps and a precise measurement of the instantaneous lunar apparent diameter. Our aim here is not to provide any improved measurement of a well- known astronomical quantity, but rather to demonstrate how the public could be engaged in scientific endeavors and how using simple instrumentation and readily available technological devices such as smartphones and digital cameras, any person can measure the local Universe as ancient astronomers did.
    [Show full text]
  • The Moon and Eclipses
    The Moon and Eclipses ASTR 101 September 14, 2018 • Phases of the moon • Lunar month • Solar eclipses • Lunar eclipses • Eclipse seasons 1 Moon in the Sky An image of the Earth and the Moon taken from 1 million miles away. Diameter of Moon is about ¼ of the Earth. www.nasa.gov/feature/goddard/from-a-million-miles-away-nasa-camera-shows-moon-crossing-face-of-earth • Moonlight is reflected sunlight from the lunar surface. Moon reflects about 12% of the sunlight falling on it (ie. Moon’s albedo is 12%). • Dark features visible on the Moon are plains of old lava flows, formed by ancient volcanic eruptions – When Galileo looked at the Moon through his telescope, he thought those were Oceans, so he named them as Marias. – There is no water (or atmosphere) on the Moon, but still they are known as Maria – Through a telescope large number of craters, mountains and other geological features visible. 2 Moon Phases Sunlight Sunlight full moon New moon Sunlight Sunlight Quarter moon Crescent moon • Depending on relative positions of the Earth, the Sun and the Moon we see different amount of the illuminated surface of Moon. 3 Moon Phases first quarter waxing waxing gibbous crescent Orbit of the Moon Sunlight full moon new moon position on the orbit View from the Earth waning waning gibbous last crescent quarter 4 Sun Earthshine Moon light reflected from the Earth Earth in lunar sky is about 50 times brighter than the moon from Earth. “old moon" in the new moon's arms • Night (shadowed) side of the Moon is not completely dark.
    [Show full text]
  • Low-Spatial-Frequency Bias in Context-Dependent Visual Size Perception
    Journal of Vision (2018) 18(8):2, 1–9 1 Low-spatial-frequency bias in context-dependent visual size perception Research Center of Brain and Cognitive Neuroscience, Liaoning Normal University, Lihong Chen Dalian, People’s Republic of China $ Research Center of Brain and Cognitive Neuroscience, Liaoning Normal University, Congying Qiao Dalian, People’s Republic of China $ State Key Laboratory of Brain and Cognitive Science, CAS Center for Excellence in Brain Science and Intelligence Technology, Institute of Psychology, Chinese Academy of Sciences, Beijing, People’s Republic of China Department of Psychology, University of Chinese Academy of Sciences, Yi Jiang Beijing, People’s Republic of China $ Spatial frequency (SF) information is essential for visual However, rather than in isolation, objects appear in a perception. By combining a sensitization procedure and spatiotemporal context. Converging evidence suggests the Ebbinghaus illusion, we investigated the effect of SF that human visual size perception is highly context- bias in context-dependent visual size perception. During dependent. For instance, an object appears larger when the sensitization phase, participants were repeatedly surrounded by small items than when the same object is presented with low- or high-pass filtered faces or surrounded by large items (the Ebbinghaus illusion). gratings and were asked to discriminate the gender or Many studies have found that human visual size the orientation of them, respectively. Immediately perception is modulated by threatening information following the sensitization phase, the Ebbinghaus illusion (Shiban et al., 2016; Stefanucci & Proffitt, 2009; van strength was measured. The results showed that the Ulzen, Semin, Oudejans, & Beek, 2008; Vasey et al., illusion strength was significantly larger when the prior sensitized images were low-pass filtered relative to 2012; Whitaker, McGraw, & Pearson, 1999), even when when they were high-pass filtered.
    [Show full text]
  • Projects of Peter Kokh, Crew #45 Commander
    Projects of Peter Kokh, Crew #45 Commander Setting a Moonlike Atmosphere in a very Marslike Setting We have little control over the Marslike geology of the MDRS surroundings - sedimentary and water- carved. However, in a test performed in a brief visit on December 8, 2005, we found that wraparound green tint sunglasses worn inside the EVA Suit helmets do a lot to neutralize the orange hues, and to notably gray and whiten the landscape. We will also apply, in a clean-remove fashion, green auto window tint to the interior of the Hab upper deck portholes. Another trick will be to suspend an Earth globe at the right distance outside one of the Hab portholes to show the apparent size and phase of Earth as it would appear suspended over the lunar horizon. Inside the Hab, the table will be set with dishes that look like they might have been made on the early lunar frontier. For recreation, there will be Moon-theme films, games that could be manufactured on the frontier, “made-on-Luna”musical instruments, and Moon-”filk”: lunar words set to well-known melodies. Our diet and menu selections, chosen by Executive Officer Laurel Ladd, will attempt to model what will be available on the early frontier. Lunar Analog EVA Outings Design It will be a bigger challenge to conduct EVA, space-suited excursions, into the areas surrounding the Mars Hab, that maintain a “we’re on the Moon!” illusion. Two particularly moonlike areas have been identified and will be visited during regular EVA excursions. Nighttime EVA activities are traditionally discouraged for safety reasons.
    [Show full text]
  • Is the Moon Really Larger Near the Horizon?
    EXPLORATION 2: INCREDIBLE SHRINKING MOON! Is the Moon really larger near the horizon? he purpose of this exploration is to design an experiment, using the telescope, to investigate the apparent size of the TMoon when it is near the horizon, compared to when it is higher in the sky. • To the eye, the Moon appears much larger when it is near horizon. GRADE LEVEL: 7-12 • Yet when the Moon is near the horizon, it is actually slightly further from Earth than when viewed higher in the sky. If TIME OF YEAR: anything, we would expect the horizon Moon to look smaller. Anytime, but best when Moon is nearly full (see text). • Measurement is important because our senses and our intuition SCIENCE STANDARDS: are often a poor guide to reality. Earth-Moon system Science as inquiry MATERIALS NEEDED: The Moon when it is near the horizon is one of nature's stunning 4Online telescopes (or use sights. It looks huge, and so close that you could practically touch it. archived images.) 4 MOImage, software Can it really be that large? What's going on? provided 4 Earth globe This investigation offers students important opportunities to learn 4 Printer (optional) about how and why we do science—from question-posing, to TIME NEEDED: forming a hypothesis, to designing an experiment, gathering 2 class periods evidence and coming to a conclusion. TEXTBOOK LINK: Students first discuss why the Moon might look so much larger when it is near the horizon. They must draw on their understandings of how the world works: What factors might influence the perceived size of an object? Second, as they reason from a simple Earth-Moon model, they are confronted with contradictory evidence: Though the Moon looks larger near the horizon, it ought to look smaller, because it is farthest From the Ground Up!: Moon 1 © 2003 Smithsonian Institution away there.
    [Show full text]
  • The Moon Illusion Author(S): Frances Egan Source: Philosophy of Science, Vol. 65, No. 4 (Dec., 1998), Pp. 604-623 Published
    The Moon Illusion Author(s): Frances Egan Source: Philosophy of Science, Vol. 65, No. 4 (Dec., 1998), pp. 604-623 Published by: The University of Chicago Press on behalf of the Philosophy of Science Association Stable URL: http://www.jstor.org/stable/188575 . Accessed: 17/02/2011 14:32 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at . http://www.jstor.org/action/showPublisher?publisherCode=ucpress. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. The University of Chicago Press and Philosophy of Science Association are collaborating with JSTOR to digitize, preserve and extend access to Philosophy of Science. http://www.jstor.org The Moon Illusion* Frances Egantl Rutgers University Ever since Berkeleydiscussed the problemat length in his Essay Towarda New Theory of Vision,theorists of vision have attempted to explain why the moon appears larger on the horizon than it does at the zenith.
    [Show full text]
  • The Moon Illusion Explained Introduction and Summary
    The Moon Illusion Explained Finally! Why the Moon Looks Big at the Horizon and Smaller When Higher Up. Don McCready Professor Emeritus, Psychology Department University of Wisconsin-Whitewater Whitewater, WI 53190 Email to: mccreadd at uww.edu Introduction and Summary [Revised 12/07/02] For many centuries, scientists have been puzzled by the illusion that the full moon at the horizon usually looks larger than it does later, at higher elevations toward the zenith of the sky. Many explanations (theories) have been offered. But, it is fair to say that the two dozen (or so) scientists most familiar with current research on the illusion have not yet accepted any one theory. The jury is still out. The theory reviewed in this article is relatively quite new (McCready, 1983, 1985, 1986). It begins with the basic assumption that, when most people say "the moon looks larger," they are referring primarily to the moon's angular subtense (McCready, 1965). That is, the horizon moon looks a larger angular size than the zenith moon. That experience is imitated if you look at the circles in the figure at the right, because the lower circle subtends a larger angle at your eye than the upper circle does. Angular Size Illusion. For the moon, that appearance is known as the moon illusion, because the angle the moon's diameter subtends at your eye measures about 1⁄2 degree of arc no matter where the moon is in the sky. That is, there is no physical (optical) reason why the horizon moon should look larger than the zenith moon: For instance, it has been known for centuries that the horizon moon is not "magnified' by the earth's atmosphere.
    [Show full text]