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from German, Gestalt can be taken to mean “whole” or “form,” an apt summary of this psy-chologic approach [1]. Expanding on the ideas of earlier theorists, these psychologic pioneers developed an encompassing definition of per-ception that differed quite strikingly from that of atomism, the predominant psychologic theory at the time. Atomists such as Wilhelm Wundt, regarded by many as the father of mod-ern psychology, believed that perception could be broken down into discrete units, each play-ing a finite role in shaping the conscious experi-ence. Gestalt theorists criticized this perspec-tive and argued for a more holistic approach [2]. They believed that the perception of any given object or experience exhibits intrinsic qualities that cannot be completely reduced to visual, auditory, tactile, olfactory, or gustatory components. Gestalt psychologists held that perceptions are not constructed in a “bottom-up” fashion from such elements but are instead perceived globally, in a more “top-down” fashion. They proposed that we have an in-nate tendency to organize sensory inputs in a manner that creates the most coherent, seam-less perception possible [2].

The term “Gestalt” is familiar to many physicians [3]. For example, medical students and residents learn to develop a global impres-sion of a patient’s health status within seconds

Gestalt Theory: Implications for Radiology Education

Nicholas A. Koontz1 Richard B. Gunderman

Koontz NA, Gunderman RB

1Both authors: Department of Radiology, Indiana University School of Medicine, 702 Barnhill Dr., Rm. 1053, Indianapolis, IN 46202-5200. Address correspondence to R. B. Gunderman (rbgunder@iupui.edu).

The Pract ice of Radiolog y • Perspect ive

AJR 2008; 190:1156–1160

0361–803X/08/1905–1156

© American Roentgen Ray Society

For many physicians, the term “Gestalt theory” evokes several associations, including the famil-iar aphorism “the whole is greater

than the sum of its parts” and images of Neck-er cubes, Rubin vases, and indistinct-appear-ing Dalmatians. For those who enjoy a back-ground in psychology, this term conjures up such names as Wertheimer, Koffka, and Köhler—men whose seminal work helped de-fine the modern notion of perception. Howev-er, it often goes unnoticed that several princi-ples of Gestalt psychology are ubiquitous in our daily life and work and have played a cru-cial role in defining our contemporary under-standing of perception. From organizational development to Internet security, and from educational psychology to clinical medicine, our daily work is powerfully shaped by the principles of Gestalt theory. As one of modern medicine’s paradigmatically visual fields, ra-diology can be illuminated by Gestalt theory and its implications for visual perception. For that reason, radiologists in training should en-joy the opportunity to develop a basic famil-iarity with Gestalt principles.

The Gestalt movement developed in Austria and Germany near the turn of the 20th century, largely through the work of Max Wertheimer, Kurt Koffka, and Wolfgang Köhler. Translated

Keywords: education, Gestalt, image interpretation, perception, psychology, radiologists, radiology

DOI:10.2214/AJR.07.3268

Received October 8, 2007; accepted after revision November 18, 2007.

OBJECTIVE. The Gestalt theory of modern psychology is grounded in the ideas that holistic rather than atomistic approaches are necessary to understand the mind, and that the mental whole is greater than the sum of its component parts. Although the Gestalt school fell out of favor due to its descriptive rather than explanatory nature, it permanently changed our understanding of perception. For the radiologist, such fundamental Gestalt concepts as fig-ure–ground relationships and a variety of “grouping principles” (the laws of closure, proxim-ity, similarity, common region, continuity, and symmetry) are ubiquitous in daily work, not to mention in art and personal life.

CONCLUSION. By considering the applications of these principles and the stereotypi-cal ways in which humans perceive visual stimuli, a radiology learner may incur fewer errors of diagnosis. This article serves to introduce several important principles of Gestalt theory, identify examples of these principles in widely recognizable fine art, and highlight their im-plications for radiology education.

Koontz and GundermanGestalt Theory and Radiology Education

The Practice of RadiologyPerspective

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of entering the room. To arrive at such an as-sessment, there is not sufficient time for “bot-tom-up” processing. Radiologists, too, have recognized the importance of Gestalt. For example, an experienced radiologist typically engages in two distinct processes when inter-preting a chest radiograph: a rapid global search, which quickly identifies normal ana-tomic content and identifies suspicious devia-tions from it (i.e., pathologic abnormalities), and a secondary systematic scan, which in-volves a careful, algorithmic study of the ra-diograph [4]. The first phase of radiographic interpretation exemplifies a Gestalt perspec-tive. This global approach plays in invaluable role in the detection of lung lesions—a role so important that its absence cannot be compen-sated for by a careful algorithmic analysis of the radiograph [5]. There is evidence that a Gestalt approach plays an important role in the interpretation of other types of radiologic examinations, such as nuclear medicine venti-lation–perfusion lung scans [6].

Although Gestalt theory did not completely explain how perception works, it elucidated several perceptual principles that remain vital to contemporary perceptual psychologists and radiologists alike. These include the principle of figure–ground relationship, and the group-ing principles of closure, proximity, similarity, common region, continuity, and symmetry [2, 7, 8]. By exploring these principles and the benefits and risks associated with them, we can help radiology learners gain a better un-derstanding of visual perception, potentially improving their diagnostic performance.

Figure–GroundAccording to Gestalt theory, one of the most

important principles organizing our percep-tion is the figure–ground relationship. It is an automatic feature of the visual system in which the focus of attention becomes the figure and all other visual input becomes the ground [8]. For any given image, the same visual stimulus can trigger multiple perspectives, depending on what is taken to be figure and what is taken to be ground [1]. Consider the classic illusion of the Necker cube, an object that withholds the depth and spatial cues that we rely on for static perception (Fig. 1). Depending on where we train our eyes, the spatial charac-teristics of the Necker cube appear to change markedly, a phenomenon commonly referred to as figure–ground reversal [9].

The Gestalt principle of figure–ground rela-tionship is exemplified brilliantly in the work of the Dutch artist M. C. Escher (1898–1972),

who was a master at creating ambiguous fig-ure–ground relationships [8]. Escher, who is best known for his clever study of impossible constructions and challenging tessellations, re-lied on this perceptual indeterminacy in many of his best-known works, such as Relativity (1953) (see www.nga.gov/collection/gallery/ggescher/ggescher-53972.0.html). Consider also Salvador Dalí’s (1904–1989) surrealist work Slave Market with the Disappearing Bust of Voltaire (1940) (see salvadordalimuseum.org/collection/collection_highlights.html), a painting that continues to serve as a prototype for the study of perception [10].

The figure–ground principle is manifest in our tendency to focus on objects that are smaller, brighter, and more centrally located in an image [2]. This phenomenon is exem-plified brilliantly in Las Meninas (1656) (see www.museodelprado.es/en/bienvenido/15-masterpieces /ficha-obra /the-family-of- felipe-iv-or-las-meninas) by Diego Velázquez (1599–1660), famous portrait of the Spanish court of King Philip IV. At first glance, the viewer’s eyes are drawn to the infanta Mar-garita, because of her central location and radiant gown [9]. On further inspection, however, we realize that the young princess is not the focal point of the portrait, but an observer of another portrait that is in the pro-cess of being painted. Even closer inspection reveals that the artist positioned off to the left side of the canvas is none other than Di-ego Velázquez, who is painting a portrait of someone who shares the same vantage point as the observer. If princess Margarita is not the subject of this portrait, then who is? A thorough search reveals the answer—King Philip IV and Queen Mariana, whose figures

are recognizable in the mirror that is hanging behind princess Margarita.

Faulty figure–ground processing in inter-preting radiologic images can lead novices astray, as when our eyes are drawn to the bright heart at the center of a chest radiograph, causing us to neglect a thorough scan of the darker and more peripheral lung fields and surrounding soft tissues. Likewise, a neophyte interpreting an abdominal CT examination may focus excessively on bright areas of con-trast enhancement, while ignoring darker fea-tures such as pneumoperitoneum. Poor appre-ciation of our stereotypical ways of handling figure–ground relationships can lead to misdi-agnosis and detrimental outcomes for patients. Developing an appreciation for the implica-tions of this Gestalt principle may represent a vital step in the transformation of a novice into a competent radiologist.

ClosureAnother key Gestalt principle is closure,

which suggests that our minds have a tenden-cy to fill in empty spaces in an apparently incomplete image to create a complete and unified figure [8] (Fig. 2). To visualize this principle, consider the Cubist movement in Modern art. The works of Pablo Picasso (1881–1973) and Georges Braque (1882–1963) rely heavily on this grouping principle, which is observed readily in Braque’s Violin and Candlestick (1910) (see collections.sfmoma.org/OBJ89.htm). A prototypic example of analytic cubism, this painting is constructed of multiple open geometric figures that serve as 2D reductions of the objects’ true 3D forms. Through the principle of closure, an observer can effortlessly identify both the violin and the candlestick in this painting.

Fig. 1—Necker cube. In this cube drawn without crucial spatial and depth clues, an observer may perceive his or her vantage point to be either above or below the cube.

Fig. 2—Principle of closure. The human mind will fill in gaps in incomplete image to create a unified figure, thus allowing an observer to perceive these objects as a rectangle, a triangle, and a circle rather than strict perception of their true forms.

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For the radiologist, the principle of closure is at play when we review and interpret se-quential axial images from a CT or MRI ex-amination. Such planar images of internal anatomy differ markedly from the 3D appear-ance of each organ, yet the experienced radi-ologist instantly perceives the whole organ’s morphology, which novices may find difficult or even impossible. The principle of closure is also at work in numerous imaging artifacts. Often radiologists are called on to interpret imaging studies that contain artifacts, such as beam-hardening artifact on CT, which distort the appearance of adjacent tissues. Consider, for example, the impact of the dense skull base on visualization of the posterior fossa and brainstem [11]. Similar pitfalls can be iat-rogenic, such as the orthopedic hardware that can compromise interpretations of MR angio-grams [12]. In such cases the novice not only must search for lesions but also must be mind-ful of the principle of closure and its quality control implications.

ProximityThe principle of proximity states that im-

age components that are physically near each other tend to be perceived as belonging to a group [2] (Fig. 3). This principle is ubiqui-tous in personal life as well as in art, and it describes perhaps the most basic definition of a group—namely, multiple objects in close spatial proximity. Consider, for example, the allegorical painting Fight with Cudgels (1820–1823) (see eeweems.com/goya/cud-gels.html), by the Spanish painter Francisco Goya (1746–1828). Widely regarded as both the last of the Old Masters and the father of

modern art, Goya painted this work as a re-action to the civil war and class disputes that had embroiled Spain. Painted late in his life and after a series of illnesses that left him deaf, this work stands out among “the Black Paintings” because of its expansive back-ground and small, simplistic figures. In this work, the principle of proximity is intention-ally used twice. At first glance, we notice two men engaged in brutal combat; however, when visualized against the expansive back-drop of the meadow landscape, the principle of proximity causes the observer to perceive the combatants as belonging together, sug-gesting some degree of alliance. In this case, Goya used the principle of proximity to cre-ate a perception that the two fighters are fel-low countrymen. The men’s legs also disap-pear deep into the quagmire below them. This fusion with the earth creates the percep-tion that these men share a strong association with the very land (i.e., the Iberian Peninsu-la) they are fighting over.

The principle of proximity plays an im-portant role in radiology. When evaluating the chest CT examination of a patient with suspected bronchogenic carcinoma, a novice radiologist may naturally assume that an en-larged hilar lymph node near the pulmonary mass is a metastatic focus. However, physical proximity does not necessarily imply a caus-al relationship, and a radiology student must learn to appreciate that proximity can prove misleading. A similar situation occurs in breast cancer, when the lymph nodes nearest the primary lesion are not necessarily the most closely connected physiologically. The use of sentinel node lymphoscintigraphy in staging such diseases is a creative imaging response to this pitfall.

The principle of proximity has metaphoric applications as well. It is common for physi-cians to perceive radiologists as isolated from the rest of the hospital. The radiology depart-ment is often located on a different floor or in a

different wing and generally exhibits a highly distinctive ambience, including very low levels of ambient lighting and noise. Such factors can lead to the impression that radiologists are med-ical outsiders. Means of counteracting such an impression would include locating radiologists’ work areas nearer to or even inside patient care areas and getting radiologists out of the radiol-ogy department and into patient care areas on a regular basis (e.g., holding ICU–radiology rounds in the ICU) [13]. In the increasingly crowded environment of medical imaging, it is vital that we remind radiology residents of the importance of their own visibility.

SimilarityThe principle of similarity holds that like-

appearing objects tend to be perceived as a group [1] (Fig. 4). This Gestalt principle can be appreciated artistically in The Burial of the Count of Orgaz (1586–1588) (see www.wga.hu/frames-e.html?/html/g/greco_el/09/index.html) by Doménicos Theotokópoulos (1541–1614), better known as El Greco. This painting depicts the burial of the pious Don Gonzalo Ruíz de Toledo, who, according to legend, was laid to rest by Saints Augustine and Stephen [14]. One of the striking fea-tures of this work is the delineation of subjects into groups based on their similar appear-ances. For example, centered at the bottom of the painting are two men (St. Augustine and St. Stephen) whose brilliant gold and red vestments allow them to be instantly per-ceived as belonging to a group entirely dif-ferent from the men in black civilian dress (the gentlemen of Toledo) or those wearing cassocks and chasubles (the priests).

The principle of similarity plays an im-portant role in radiology education because the ability to formulate an extensive and ap-propriate differential diagnosis is an impor-tant factor that separates a novice from a competent radiologist. A major component of formulating a differential diagnosis is

Fig. 3—Principle of proximity. Objects that are physically near each other tend to be perceived as belonging in a group rather than as individual objects, thus allowing observer to perceive this image as three groups of four circles rather than 12 independent circles.

Fig. 4—Principle of similarity. Objects that bear a similar resemblance tend to be perceived as belonging in a group. In this case, an observer readily perceives five columns of black squares and five columns of white squares rather than four rows containing black and white squares.

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perceiving similarities and differences be-tween imaging findings. Consider the finding of an abnormally increased cardiothoracic ratio on a frontal chest radiograph. Presented with such a finding, the neophyte may im-mediately launch into a differential diagnosis of cardiomegaly, including congestive heart failure, dilated cardiomyopathy, valvular heart disease, metabolic disorders, and so on. Only with experience does the learner appreciate that there are a number of impor-tant cardiomegaly mimics, including antero-posterior technique, underinflation, pectus excavatum, and pericardial effusion. More-over, only with experience does the radiology student become adept at correlating the per-ception of similar appearing abnormalities with accurate differential diagnoses.

Common RegionThe Gestalt principle of common region

states that objects or stimuli that are enclosed in a common region are likely to be perceived as a group, regardless of similarity or near-ness of the constituent objects or stimuli [7] (Fig. 5). This principle is evident in the chal-lenging artwork of the Belgian surrealist painter René Magritte (1898–1967), who is best known for taking ordinary objects and injecting them into unrealistic and impossi-ble settings. Magritte frequently placed un-related objects in common environs, causing the observer to perceive them as related to one another [15]. One such example is his painting Les Valeurs personnelles (Personal Values) (1952) (see www.sfmoma.org/mso-ma/artworks/5139.html), a surrealist investi-gation into the relationship between humans and ordinary personal items of daily life. When the artist places larger-than-life, in-congruous objects such as a comb, a bar of soap, a wine glass, a matchstick, and a shav-

ing brush within the confines of a bedroom, the observer perceives these seemingly unre-lated objects as intrinsically connected, al-beit a connection that the observer cannot readily identify. Magritte draws the observer into the work by inviting us to draw on our own experiences in seeking a unifying theme among the objects.

The principle of common region is a key grouping principle for the radiology learner because of its implications for the formation of appropriate differential diagnoses. For ex-ample, the mediastinum can be divided spa-tially into three compartments: anterior, middle, and posterior. When a mediastinal mass is identified on chest radiography or a chest CT scan, we attempt to locate it accord-ing to this anatomic scheme. Likewise, in interpreting images of the CNS, classifying a mass as intraaxial or extraaxial is a crucial step in formulating a differential diagnosis. The same can be said for intra- and extra-peritoneal processes, arterial versus venous processes, and abdominal versus pelvic pro-cesses. By developing an appreciation of our natural tendency to perceive objects com-partmentally, a learner may become more adept at correlating imaging findings with pathologic processes.

ContinuityThe principle of continuity states that

smooth, continuous lines can be perceived more effortlessly than interrupted lines [2] (Fig. 6). This Gestalt principle was used by the enigmatic Marcel Duchamp (1887–1968) in his controversial work Nude Descending a Staircase (No. 2) (1912) (see www.philamu-seum.org/collections /permanent /51449.html). Composed solely of interrupted lines painted in successive planes, we cannot per-ceive a static image of the nude figure due to

perceptual limitations imposed by this prin-ciple. Instead, we perceive these broken lines in a staccato fashion, imparting the percep-tion that the figure is in motion. One of the earliest artists to attempt to represent motion in paint, Duchamp used the hallmark tech-niques of analytic cubism (i.e., limited pal-ette and form deconstruction) both to tran-scend the static confines of cubist art and to rebuke its pretensions [16].

This principle plays an important role in the interpretation of skeletal radiographs, such as clearing a cervical spine in a trauma patient or attempting to detect child abuse on a skeletal survey. When reading a lateral cer-vical spine radiograph, we learn to see imag-inary anatomic lines: the anterior vertebral line, posterior vertebral line, spinolaminal line, and posterior spinal line. Using the imagination to create such mental images enables radiologists to reliably detect cervi-cal injuries. However, when deviations from these lines are subtle, perceiving signs of in-jury can be painstakingly difficult. Particu-larly in the case of suspected child abuse, the radiology student must exercise great care in scanning for subtle deviations from the nor-mal bone contours, because the principle of continuity suggests that slight deviations (such as bucket-handle fractures and pe-riosteal reaction) may be difficult to detect in the setting of otherwise normal findings. By emphasizing the implications of the principle of continuity at an early stage of radiology education, we help learners guard against perceptual pitfalls.

SymmetryThe Gestalt principle of symmetry holds

that symmetric objects or stimuli tend to be perceived as a group regardless of proximity (Fig. 7). This is perhaps one of the most

Fig. 5—Principle of common region. Objects that are enclosed within common region are likely to be perceived as belonging in a group, regardless of similarity or nearness of constituent objects. In this case, unrelated objects are perceived as belonging to a group because they are confined in a common structure, whereas similar objects outside this structure are not perceived as belonging with their mates.

A

C

B

D

Fig. 6—Principle of continuity. Visual stimuli consisting of smooth, uninterrupted lines can be perceived more effortlessly than interrupted lines. In this case, lines AB and CD are more easily perceived than lines AC, AD, BC, or BD.

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ubiquitous of the Gestalt grouping principles encountered in fine art and in daily life. Con-sider the iconographic painting The Mar-riage of Giovanni Arnolfini and Giovanna Cenami (1434) (see www.nationalgallery.org.uk/cgi-bin/WebObjects.dll/Collection Publisher.woa /wa /work?workNumber= NG186) by Jan van Eyck (c. 1385–1441). At first glance, the symmetric positioning of the subjects, including the centrally located dog, leads us to suppose that the subjects be-long together as a group. With further study, however, we can appreciate a hidden sym-bolism, which strongly suggests that the painting reflects either an engagement or marriage [9]. Consider also The Last Supper (c. 1495–1498) (see www.cenacolovinciano.it/html/eng/home. htm) by Leonardo da Vin-ci (1452–1519). The symmetry of the com-position contributes to a one-point linear perspective, and it allows the apostles to be instantly perceived as belonging to a group, with all attention focused on Christ’s head, the painting’s focal point [9].

Radiologists use the principle of symme-try regularly in evaluating the lungs, bones, and cerebral hemispheres, which are nor-mally relatively symmetric. With experience, a competent radiologist will judiciously use

this principle to detect various abnormalities that disrupt the anatomic symmetry. Howev-er, the same principle can mislead a novice when the pathology is bilateral and symmet-ric. Consider, for example, isodense bilateral subdural hematomas, or cleidocranial dys-plasia, with the absence of the clavicles. To the veteran radiologist, these might represent rather straightforward diagnoses, but we must be mindful that learners can be fooled by pathology that is symmetric.

ConclusionGestalt principles of visual perception play

an integral but often underappreciated role in both radiology practice and the training of future radiologists. By familiarizing ourselves with these ubiquitous principles at an early stage of training, we can help radiology stu-dents better understand the unconscious work involved in interpreting radiologic images and prepare them to avoid common percep-tual pitfalls.

References 1. Myers DG. Psychology, 5th ed. New York, NY:

Worth Publishers, 1998

2. Davis SF, Palladino JJ. Psychology: media and

research update, 3rd ed. Upper Saddle River, NJ:

Prentice Hall, 2002

3. Feddock CA. The lost art of clinical skills. Am J

Med 2007; 120:374–378

4. Kundel HL, Nodine CF. Interpreting chest radio-

graphs without visual search. Radiology 1975;

116:527–532

5. Oestmann JW, Greene R, Bourgouin PM, Li-

netsky L, Llewellyn HJ. Chest “Gestalt” and de-

tectability of lung lesions. Eur J Radiol 1993;

16:154–157

6. Hagen PJ, Hartmann IJC, Hoekstra OS, Stokkel

MPM, Teule GJJ, Prins MH. How to use a Gestalt

interpretation for ventilation–perfusion lung

scintigraphy. J Nucl Med 2002; 43:1317–1323

7. Coon D. Essentials of psychology: exploration

and application, 7th ed. Cincinnati, OH: Brooks/

Cole, 1997

8. Halonen JS, Santrock JW. Psychology: contexts

of behavior, 2nd ed. Chicago, IL: Brown &

Benchmark, 1996

9. Sayre HM. A world of art, 3rd ed. Upper Saddle

River, NJ: Prentice Hall, 2000

10. Bonnar L, Gosselin F, Schyns PG. Understanding

Dali’s Slave Market with the Disappearing Bust of

Voltaire: a case study in the scale information

driving perception. Perception 2002; 31:683– 691

11. Earnest F, McCullough EC, Frank DA. Fact or

artifact: an analysis of artifact in high resolution

computed tomographic scanning of the sella. Ra-

diology 1981; 140:109–113

12. Fidelman NA, Wilson MW, Bloom AI, Kerlan

RK, LaBerge JM, Gordon RL. Orthopedic spinal

and hip prostheses: effects of magnetic suscepti-

bility artifacts during MR arteriography and

venography of abdomen and pelvis. Radiology

2006; 240:894–899

13. Friedenberg RM. Au revoir, but not goodbye. Ra-

diology 2004; 232:319–323

14. Miranda R. Toledo: its art and its history. Tole-

do: Artes Gráficas Toledo, SAU, 1999

15. Gohr S. Magritte. New York, NY: Harry N.

Abrams, Inc., 2000

16. Stafford A. Three paintings. Making sense of

Marcel Duchamp. www.understandingduchamp.

com. Accessed August 5, 2007

Fig. 7—Principle of symmetry. Symmetric objects or stimuli tend to be perceived as belonging to a group regardless of their proximity to one another. In this case, the observer will perceive both the brackets and the triangles as belonging with their mirror image because of principle of the symmetry. Crescent and hexagon form asymmetric image; therefore, they are not perceived as belonging together.