an interactive test of color and contour perception by artists and non-artists

Leonardo

An Interactive Test of Color and Contour Perception by Artists and Non-ArtistsAuthor(s): Dorothy K. WashburnSource: Leonardo, Vol. 33, No. 3 (2000), pp. 197-202Published by: The MIT PressStable URL: http://www.jstor.org/stable/1577044 .

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GENERAL ARTICLE

An Interactive Test of Color

and Contour Perception by Artists and Non-Artists

Dorothy K. Washburn

lermanent forms of visual imagery, long thought to "begin" with the hauntingly realistic depictions of fauna in cave art from the Upper Paleolithic, are now known to have more ancient roots [1]. But, whatever the date of the "first" art, the fact that permanent depictions are associated with some of the earliest human occupational evidence suggests that for human beings imagery must have some important, life-sustaining role. Otherwise, the elaboration of all kinds of surfaces with everything from realistic depictions to geometric pattern would not be so ubiquitously practiced by every society in the world.

While stylistic analyses exist for just about every type of visual expression, mere description does not explain why humans depict things the way they do. For example, stylistic analyses cannot explain why animals in the early cave paintings were rendered in simple profile outlines rather than in some other format. An important part of the explanation for why humans have widely employed certain ways of visually project- ing images and why these images are such effective communi- cators of human ideas and emotions lies in the fact that these

projective systems highlight basic features of form that are fo- cal points in the perceptual processing of stimuli by all human viewers, regardless of their expertise. Recent work in perceptual psychology has revealed that certain elements of form that our eye distinguishes and puts together in order to recognize shape are the building blocks of vision. Perceptual psy- chologists have called these forms "primitives" because they comprise the fundamental parts of form, such as the lines, angles and curvatures that delimit all form. In addition, our

eye also focuses on certain properties of each form, such as its color, symmetry, orientation and texture [2]. Richard Latto has proposed that effective images capture our attention and communicate emotions and ideas because the artists that create them have homed in on the basic properties of form that the human visual system has specifically evolved to detect [3].

While this proposal-that artists use certain fundamental features of form to communicate most effectively-is intu-

itively attractive, the theory that viewers of art, whatever their

expertise, visually and cognitively respond to these same features must be empirically confirmed. It would be monumen- tally ineffective if artists utilized features that everyone else did not see and process. Furthermore, a finding that non-artists focus on the same features as do artists would pave the way for analysts to use these features as the basis for meaning- ful investigations of how art performs a number of different communicative functions. In short, then, we could state more

confidently that art as a form of visual communication achieves its effectiveness via certain fundamental features and properties of form. In order to clarify what these features are and who sees them, I have developed a new

methodology that captures the criteria used by viewers as they examine developing rather than static images.

ABSTRACT

The author explores Richard Latto's proposition that art com- municates effectively because artists manipulate basic features of form that the human perceptual system has evolved to detect. She offers an empirical test of the correlated proposition-that viewers of art use these same features to assess art. The author presents the results of an experi- ment in which both artists and non-artists were asked to discern and draw shapes in patterns defined by iterating dots. She finds that both groups used color in the case of positive shape and form edge in the case of negative space, thereby confirming that both makers and viewers of art focus on the same kinds of features to recognize and assess form.

STIMULI One factor that affects the perception of stimuli is prior knowledge. Although conventional wisdom tells us that cultural learning affects and directs what our eye perceives, ex-

actly how knowledge affects perception and when this occurs in perceptual processing has not been well studied. Anthropo- logical studies have detailed only how the particular expertise used by artisans who make objects and by individuals who use these objects affects how objects are classified in folk taxono- mies [4]. In contrast, psychological eye-tracking studies have explored how objects are examined. For example, C.F. Nodine, P.J. Locher and E.A. Krupinski found that individuals with different levels of art expertise use different looking strategies [5]. Artists used a more global looking strategy, focusing on the relationships among compositional features, while viewers with no art training preferentially looked at features that had specific interest or recognizable identity and meaning to them. But because these results were obtained when viewers were asked to examine representational images, the content of which may have differentially affected the looking activity of those with different levels of expertise, in this study I showed respondents nonrepresentational patterns composed of geometric shapes used by cultures all over the world [6].

RESPONDENTS

The respondent pool included individuals with different degrees of art training and art experience. The artist pool con- sisted of studio faculty and art students at The Maryland In- stitute College of Art in Baltimore, Maryland. The studio

Dorothy K. Washburn (anthropologist), Maryland Institute, College of Art, 1300 Mount Royal Ave., Baltimore, MD 21217, U.S.A. E-mail: <[email protected]>.

LEONARDO, Vol. 33, No. 3, pp. 197-202, 2000 197 ? 2000 ISAST



faculty is a distinguished group of

teaching and practicing artists; the students were juniors and seniors at the

college. The responses of these two sub-

groups of art-trained individuals were

compared to responses by staff and fac-

ulty from the Maryland Institute who had no art training.

PROCEDURE Most studies that attempt to discern what kinds of things viewers look at use eye- tracking procedures. These studies have

richly rewarded investigators with insights about viewer looking activity by recording how and what individuals look at when

viewing images [7]. For representational

images, A.L. Yarbus observed different

eye-scan pathways when subjects were asked to respond to a series of questions about the social position of the individuals depicted, the activities they are en-

gaged in, their ages, etc. [8]. Each ques- tion required them to look at different

aspects of the image. Locher and Nodine found that viewers use a two-stage viewing strategy, initially making a global survey of the image with many short gaze fixations and then examining specific features with a series of longer gazes [9].

For non-representational images, M. Baker and M. Loeb [10] observed that viewers fixated on the information-

bearing sections, i.e. the corners of

polygons, points of difference in

Fig. 1. The six one-color, two-dimensional plane patterns shown to artists and non-artists.

Top row: left, cm; right, pgg. Middle row: left, pmg; right, p3. Bottom row: left, p4g; right, p4m. The iteration sequence began with a random array of dots and required from 7,000- 15,000 iterations to achieve the density shown here. However, few viewers needed this ex- tensive development to see the pattern. Most stopped the progression after about 300-800 iterations, as shown in the examples in Fig. 2. (? Dorothy Washburn)

t~~~~~~~~; .!;

histoform height, and changes in line direction in closed-line, unfamiliar geometric figures that were created with a

specially written software program on a

Vargus 10 computer [11]. These results complement studies

that have shown that the most important information about shape is embedded in changes in contour rather than along the straight (and thus redundant) parts of a shape outline [12]. For example, individuals scanning a face shown in

profile look along the edge of the profile because that edge contains the cur- vature information that identifies it as a face [13]. Such "areas of high information content" are not only deemed more informative but also receive up to four times as many fixations as the redundant and thus uninformative areas [14].

But because eye-fixation studies record everything viewers look at and do not discriminate between fundamental

parts of form and whole forms, I sought to develop a new procedure that would enable me to focus on the fundamentals of form that viewers use in the early rec-

ognition stages of visual processing. To do this, I had to find new ways both to

present stimuli and to ask viewers to re-

spond to the stimuli. Rather than asking viewers to look at a fully formed image, I presented viewers with arrays of random dots on a computer screen that de-

veloped into an image gradually as dots were added. In addition to asking viewers to press a pause button when they discerned the pattern, I asked them to sketch the pattern they saw. I contend that the criteria viewers used to recognize patterns in the paused images were

captured in the sketches they made. This approach requires only the assump- tion that, in order to draw the pattern, viewers used those criteria to see it.

I tested viewers individually as they sat in front of a computer screen. I in- structed them to respond to the formation of a series of two-dimensional plane patterns being generated on the moni- tor, but did not define what constituted a

"pattern." In the discussion after the test-

ing I found that everyone, artists and non-artists alike, examined the iterating dots from the generally held premise that "pattern" refers to repeating images.

Each pattern began as a random array of dots and, through successive iterations, evolved into a clearly defined, re-

peated pattern. The dot density in- creased with each iteration. The

respondents were asked to stop the iteration sequence when they first saw a

pattern appear and then to sketch the

198 Washbur: An Interactive Test of Color and Contour Perception



pattern they saw. They were allowed to refer to the screen while making their sketches. Both the sketch and a screen

dump printout of the image recorded what they had seen [15].

I used the pattern-generating program as originally written [ 16]; however, the iterating sequence on the 486 PC was too slow for complex pattern param- eter combinations and would have re-

quired respondents to spend 30 minutes or more watching very complex patterns develop-clearly a viewing time longer than that used in most tests of perceptual activity. So I selected simple patterns that developed into clearly defin- able images in less than 5 minutes. The slow iterating sequence on the 486 was desirable, however, since the pauses between iterations allowed time for viewer

inspection and response [17].

VIEWER RESPONSE TO TWO-COLOR PA1FTERNS Given the well-established way in which color distinctions enable viewers to

"identify which elements in a complex visual field belong together" [18], I

sought to test how color was used in pattern recognition. I showed five different color patterns from three two-dimensional (2D) symmetry classes (pg#l, pg#2, p4g#1, p4g#2, p6) (Color Plate A No. 3) to 11 art students and five faculty and staff who had no art training. While color undoubtedly always contributes in an important way to the realism of representational images and thus influences how individuals look at such im-

ages, the results reported here indicate that the presence of color also affects the looking activity of both artists and non-artists when they view non-representational dot patterns.

The iteration program produced patterns with two colors: red and green. During the initial iterations, the two colors appeared randomly distributed. With further iterations, viewers distin-

guished the element shapes primarily by color difference. That is, the drawings made by both artists and non-artists

clearly show that areas of color homoge- neity were the primary cues that viewers used to define the shape of the elements and thus the pattern.

For example, in pattern p4g#2 the red and green dots were distributed so that viewers defined the motif shapes by the way the groups of line segments were

similarly colored. Adjacent red and

green line segments formed hourglass figures that were aligned in rows angled

either to the left (red) or to the right (green). Viewers' drawings of this pattern (such as the one to the left of pattern p4g#2) clearly indicate how they vi-

sually grouped the similarly colored line

segments into hourglass figures. Indeed, as predicted by Gestalt principles of

proximity and similarity [19], the viewers focused on the holistic units of color. For the p4g#2 pattern, these holistic lines of color formed hourglass motifs.

VIEWER RESPONSE TO ONE- COLOR PAI'TERNS I compared the results from viewer reac- tions to colored patterns to their reac- tions to black-and-white patterns. I showed six different one-color two-dimensional patterns (cm, pgg, pmg, p3, p4g, p4m) (Fig. 1) to 24 art students, 12 studio art faculty and 13 staff without

any art training. Ideally I would have

compared viewer response to the same

patterns in the same symmetry structure classes for both color and black-and- white patterns. However, because the colored patterns iterated too fast when run in black and white, I had to choose a new series of patterns.

Pattern name Number of subjects Number of correct answers Number using negative strategy Number using positive strategy Number correct answers for negative strategy Number correct answers for positive strategy

Pattern name Number of subjects Number of correct answers Number using negative strategy Number using positive strategy Number correct answers for negative strategy Number correct answers for positive strategy

Number of subjects Number of correct answers Number using negative strategy Number using positive strategy Number correct answers for negative strategy Number correct answers for positive strategy

Under normal viewing situations, viewers use sharp line distinctions to define shape contours [20]. But with my dot stimuli experiments, viewers had to

replace continuous line boundaries with

figures defined by groupings of dots.

Particularly during the early stages of

pattern iteration, the "positive" patterns, as defined by the dots, were often difficult to see since they had highly "ragged" edges because the dots were few and widely spaced. Nevertheless, the results clearly showed that all viewers, regardless of training, looked for contour-the outline of shape.

Viewers used two strategies to look for contour in these indistinct stimuli. Tables 1, 2 and 3 show how viewers with different training responded to the six

patterns. The majority (70%) of both the art-trained and untrained viewers looked at the negative background space in order to discern figure shape, a method of viewing that I will refer to as the "negative strategy." The bias for use of the negative strategy was significant at the 95% confidence level for four of the six patterns (cm, pmg, p4g, and p4m; 52 =

23.6, 23.6, 52.0 and 6.6, respectively, with ldf [21]). Only 30% of the viewers

cm

12 6

11 1 6 0

cm p3 24 24 14 8 21 15

3 9 14 6 0 2

13 4

10 3 3 1

p3 11 5 5 6 3 2

13 4 9 4 3 1

pmg 12 8

10 2 8 0

pmg 24 20 20

4 19

1

13 9

12 1 9 0

pgg 11 6 8 3 5 1

pgg 24 12 13 11 10 2

13 3 7 6 3 0

p4g 12

2 6 6 2 0

p4g 24

3 13 11 3 0

13 1

11 2 1 0

p4m 12 7 6 6 5 2

p4m 24 15 18 6

14 1

p4m 13 11 10 3

10 1

Washburn: An Interactive Test of Color and Contour Perception 199

Table 1. Pattern Recognition by Studio Faculty as a Function of Viewing Strategy and Pattern Type

Table 2. Pattern Recognition by Art Students as a Function of Viewing Strategy and Pattern Type

Table 3. Pattern Recognition by Non-Artists as a Function of Viewing Strategy and Table 3. Pattern Recognition by Non-Artists as a Function of Viewing Strategy and Pattern Type

Pattern name cm D3 pmg Dgg pD4

I



saw the patterns in the positive-that is, in the groupings of dots. I will refer to this method of viewing as the "positive strategy."

While it is common to think of negative space in a pattern as having a sec-

ondary role as background, in these tests viewers used the edge of the negative space as the primary shape-defining cue, as confirmed in their drawings. Viewers defined the pattern shapes by outlining the background spaces. For

example, the shapes of the motifs in the

pmg, cm and p4m patterns are clearly vis- ible in the blank background in the

paused screen printouts and in the viewers' outline drawings of those back-

ground shapes (Fig. 2).

The strategy of looking at the negative space not only made it easier to see the

pattern but also resulted in a higher number of correct recognition responses. Sixty percent of viewers using the negative strategy successfully discerned the

pattern. In contrast, only 16 percent of the viewers who used the positive strategy discerned the correct pattern.

In short, because human visual processing seeks out the primitive feature of

edge when defining shape, it is not sur-

prising that-especially when viewing an indistinct array-viewers will use a look-

ing strategy that focuses on the contour

edges of areas that are clearly defined. In the patterns viewed in these tests, shape distinction based on contour edge did

Fig. 2. Viewer drawings of three iterated patterns (left images) compared with their corre- sponding computer-generated 2D plane patterns (right images). Top, pmg; center, cm; bottom, p4m. Note that, in each, the viewer saw the pattern as the shape defined by the edge of the negative space, rather than as a shape defined by a positive grouping of dots. (? Dorothy Washburn)

-?-aii- . .T:: . .': .] C .

<$6'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.'

fs9t I r t

" . ... . " . . . .. - -. - .. *

....,-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~i ,, . .

,,. ,.. ~..~P ~'..~~?

not occur until the number of iterations had contributed enough dots to produce a solid dotted "positive" area with a sharp border equivalent in visual strength to the negative areas without dots.

The fact that both trained and untrained viewers focused on negative, blank spaces to define the pattern suggests that everyone presented with this kind of indistinct stimuli, regardless of

training or expertise, looks for the same kinds of featured cues. For the cm, pmg and pgg patterns, there was a statistically significant difference in the use of the

negative recognition strategy and correct identification of the pattern (c2 = 4.8, p < 0.05; c2 = 7.6, p < 0.01; c2 = 9.8, p < 0.01, respectively).

These results suggest that the differences in looking at representational art that are related to expertise (i.e. that artists focus on compositional factors while non-artists focus on motifs) do not seem to apply to looking at nonrepresentational art. Both artists and non-artists seek to define shapes in geometric patterns dynamically presented in dotted format by searching for contour definition.

I examined two potential confounds that could affect this conclusion. First, differences in pattern symmetries might possibly affect ease of pattern recognition. This issue is difficult to control since, by definition, each of the 17 plane pattern symmetry classes is generated by different symmetries. Thus one cannot

possibly assert that the six patterns shown to viewers, each based on different symmetries, are equivalent in terms of ease of recognition. Indeed, the statis-

tically significant difference in correct

pattern identification (c2= 51.3 with 5df) suggests that some patterns are easier to recognize correctly than others (Table 4). That is, viewers drew some

patterns in the correct symmetrical lay- out more frequently than they did other

patterns. Pattern p4gwas the most difficult to discern and thus draw correctly, while pmg and p4m were the easiest to detect and draw. However, the ease of

recognition of the correct symmetry was not correlated with the kinds of features viewers used to define a pattern.

It is also possible that the results may be unique to dot stimuli. W. Uttal [22] has cautioned that conclusions about form detection using dot stimuli should be restricted to that stimuli. Yet the stun-

ning success with which the Impression- ist painter Georges Seurat created forms from masses of dots that appear to have

edges, coupled with the results reported

200 Washburn: An Interactive Test of Color and Contour Perception



Table 4. Pattern Recognition as a Functior

Pattern name

Number of subjects Number of correct answers Number using negative strategy Number using positive strategy Number correct answers for negative strateg Number correct answers for positive strategy

here, suggests that the human eye is able to detect shape along edges formed

by a wide variety of artistic devices.

CONCLUSION The work reported here has shown, us-

ing a new experimental methodology, that the fundamental features of color and contour are used by all individuals, regardless of expertise, in the recognition of one type of nonrepresentational art-geometric pattern. The results indicate that, when patterns were comprised of two colors, viewers used homoge- neous areas of color to define motifs and thus pattern. However, when the

patterns were of one color, viewers defined pattern parts by searching for

shape contour. This contour was best defined along the edge of the negative, undotted background areas.

These results highlight the saliency of color and form edge as primary at- tributes in the visual recognition of

shape. J. Mollon's observation that color vision is particularly important in situations "when the background is dappled and ... we cannot use form or lightness to find our target" [23] is well illustrated in the colored-dot geometric patterns shown in these tests that projected "var-

iegated" visual arrays. In the absence of color, however, the

most essential feature of form definition is a contour edge that distinguishes figure from background. In fact, so fundamental is outline that other kinds of information-color, texture, motion, depth-can be eliminated and yet form can still be detected [24]. The preemi- nence of this property was demonstrated

many years ago by T.A. Ryan and C. Schwartz [25], who presented subjects with four representations of an object: a black-and-white photograph, a detailed

drawing, an outline drawing and a cartoon. They found that the photograph- which supplied the greatest amount of detail about the object-took the longest to identify, while the cartoon and simple outline drawings were recognized more

quickly. The research presented in this

1 of Viewing Strategy and Pattern Type

cm p3 pmg pgg p4g 49 48 49 48 49 24 17 37 21 6 42 29 42 28 30

7 19 7 20 19 y 23 12 36 18 6

1 5 1 3 0

p4m 49 33 34 15 29

4

paper reinforces J. Hochberg's observation that outline images, stripped of em-

bellishing distractors, allow the eye to focus immediately on the essential "canonical features" that give form its

specific identity [26]. Significantly, neither training nor ex-

perience seems to affect the looking strategies used to assess pattern. I observed no strong, statistically significant difference in the use of the two strategies by art faculty, art students or staff without art training. If these results are ap- plied to the interpretation of real-world

art-making and art-viewing activities, they suggest that, regardless of expertise, makers and viewers focus on the same kinds of features in order to recognize and assess form. Indeed, more than a decade ago S. Pinker questioned the ex- tent to which knowledge plays a role in

recognizing shape [27]. He argued then that it was unclear what kind of knowl-

edge viewers use to recognize shape and how that knowledge is used in the search for features and wholes. The results from this study suggest that the information that viewers, regardless of expertise, use to discern shape in a "noisy" (i.e. dotted) environment involves color and, when no color is present, the edge and bound-

ary of the shape. Furthermore, these results indicate

that, while most people conceptualize form as positive shape, people will, when

necessary, see form in negative space. These results should lead us to recon- sider our distinction between figure and

ground. As M.A. Peterson and B.S. Gibson suggest, we typically see figures as entities endowed with shape that oc- clude backgrounds [28]. Backgrounds are seen as shapeless entities, especially near the borders they share with figures. But although one can assess fully formed images via this figure/ground concept, one cannot use it to describe the process by which viewers discern emerging shapes. The results reported here for dotted images reveal not only that the

process of shape recognition occurs at the edge, but also that the shape is rec-

ognized in the negative space.

Finally, these results compel us to re- consider the assumptions surrounding the influences of experience and expertise on the process of visual perception. If we attempt to isolate from the context of culturally learned preferences those fundamental, visually salient features and properties of form involved in the

process of form recognition, we find that both artists and non-artists-who

possess different culturally derived

knowledge about art-examine the same basic features of form.

It is thus little wonder that the same features that artists manipulate so

poignantly to communicate the great truths of human existence are intuitively detected, assessed and understood by all viewers, regardless of their cultural back-

ground and expertise.

Acknowledgments I am greatly indebted to the Maryland Institute faculty for many insightful discussions as well as to the students and staff who participated in this project. I especially thankJudy Lidie for her intellectual in-

put and organizational assistance, Myna Chen for assistance in administering the tests, Mike Field and Martin Golubitsky for sharing their pattern- generating program, Hadley Garbart for computer expertise, Frank Shen for statistical analyses and Diane Humphrey for comments on an earlier ver- sion of this paper.

References and Notes

1. A. Marshack, "Paleolithic Image Making and

Symboling in Europe and the Middle East: A Com-

parative Review," in M. Conkey et al., eds., Beyond Art, Memoirs of the California Academy of Sci- ences, No. 23 (San Francisco, CA: California Acad-

emy of Sciences, 1997) pp. 53-91.

2. A. Triesman and S. Gormican, "Feature Analysis in Early Vision: Evidence from Search Asymme- tries," Psychological Review 95, No. 1, 15-48 (1986); see also A.P. Witkin and J.M. Tenenbaum, "On the Role of Structure in Vision," in J. Beck, B. Hope and A. Rosenfeld, eds., Human and Machine Vision (New York: Academic Press, 1983) pp. 481-543.

3. R. Latto, "The Brain of the Beholder," in R. Gre-

gory,J. Harris, P. Heard, and D. Rose, eds., The Art-

fulEye (Oxford, U.K.: Oxford Univ. Press, 1995) pp. 66-94.

4. J.W.D. Dougherty and C.M. Keller, "Taskonomy: A Practical Approach to Knowledge Structures," American Ethnologist 9, No. 4, 763-774 (1982); see also J.S. Boster andJ.C. Johnson, "Form or Func- tion: A Comparison of Expert and Novice Judg- ments of Similarity among Fish," American Anthro- pologist 91, No. 4, 866-889 (1989); D. Washburn and A. Petitto, "An Ethnoarchaeological Perspec- tive on Textile Categories of Identification and Function," Journal of Anthropological Archaeology 12 (1993) pp. 150-172; C.M. Keller and J.D. Keller, Cognition and Tool Use: The Blacksmith at Work (Cam- bridge: Cambridge Univ. Press, 1996).

5. C.F. Nodine, PJ. Locher and E.A. Krupinski, "The Role of Formal Art Training on Perception and Aesthetic Judgment of Art Compositions," Leonardo 26 No. 3, 219-227 (1993).

6. The patterns presented were generated by different combinations of geometric symmetries in the two-dimensional plane. It should be emphasized, however, that this study was not testing whether individuals can differentiate between the different

Washburn: An Interactive Test of Color and Contour Perception 201



symmetries but rather was simply using the symmet- ric patterns as the presentation vehicles in order to

explore the kinds of features individuals look at when they examine nonrepresentational images. See D.K. Washburn and D.W. Crowe, Symmetries of Culture: Theory and Practice of Plane Pattern Analysis (Seattle, WA: University of Washington Press, 1988).

7. G. Buswell, How People Look at Pictures: A Study of the Psychology of Perception in Art (Chicago: University of Chicago Press, 1935); see also G.R. Loftus, "Eye Fixations and Recognition Memory for Pictures," Cognitive Psychology 3 (1972) pp. 525-551;J.R. Antes andJ.G. Penland, "Picture Context Effects on Eye Movement Patterns," in D.F. Fisher, R.A. Monty and J.W. Senders, eds., Eye Movements: Cognition and Vi- sual Perception (Hillsdale, NJ: Erlbaum, 1981) pp. 157-170; A.G. Gale, "Human Response to Visual Stimuli," in W. Hendee and P. Wells, eds., The Per- ception of Visual Information (New York: Springer- Verlag, 1993) pp. 115-133.

8. A.L. Yarbus, Eye Movements and Vision (New York: Plenum, 1967).

9. P.J. Locher and C.F. Nodine, "Symmetry Catches the Eye," inJ.K. O'Regan and A. Levy-Schoen, eds., Eye Movements: From Physiology to Cognition (New York: Elsevier, 1987) pp. 353-361.

10. M. Baker and M. Loeb, "Implications of Mea- surement of Eye Fixations for a Psychophysics of Form Perception," Perception & Psychophysics 13, No. 2, 185-192 (1973).

11. For a description of the Vargus 10 computer program used to generate the nonrepresentational images, see M.A. Hastings and S.H. Evans, "The Se- lection of Local Features for Pattern Identification: An Exploratory Study" (U.S. Army Technical Memorandum, 1970) pp. 5-70.

12. F. Attneave, "Some Informational Aspects of Vi- sual Perception," Psychological Review 61, No. 3, 183-193 (1954).

13. Yarbus [8].

14. N.H. Mackworth and AJ. Morandi, "The Gaze Selects Information Details within Pictures," Percep- tion & Psychophysics 2, No. 11, 547-552 (1967).

15. While the screen dump printouts shown in this article have black dots on a white background, the images viewers saw on the screen were white dots on a black screen. For reasons of clarity in seeing the pattern and printing this article, the color scheme has been reversed.

16. The software used to create these patterns was BASIC, and the whole algorithm was published in Appendix B in M. Field and M. Golubitsky, Symme- try in Chaos: A Search for Pattern in Mathematics, Art and Nature (Oxford: Oxford Univ. Press, 1992).

17. A 486 DX Quantex PC, 15-in Goldstar SVGA screen, Hijaak Pro screen capture software, HP Deskjet 1200/PS printer were the equipment used. The program was run through DOS and Windows 3.1 so that it would iterate slowly enough for con- sidered responses.

18. J. Mollon, "Seeing Colour," in T. Lamb andJ. Bourriau, eds., Color: Art & Science (Cambridge: Cambridge Univ. Press, 1995) p. 141.

19. Stephen E. Palmer, "Modern Theories of Ge- stalt Perception," in Glyn W. Humphreys, ed., Un- derstanding Vision (Oxford, U.K.: Blackwell, 1992) pp. 39-70.

20.J.R. Pomerantz, E.A. Pristach and C.E. Carson, "Attention and Object Perception," in B. Shepp and S. Ballesteros, eds., Object Perception: Structure and Process (Hillsdale, NJ: Erlbaum, 1989) pp. 53-89.

21. The term "df," degrees of freedom, refers to the number of independent variables that describe a set of data. "Confidence level" corresponds to the

percent probability that the finding is not merely the result of chance.

22. W. Uttal, The Perception of Dotted Forms (Hillsdale, NJ: Erlbaum, 1987).

23. See Mollon [18] p. 136.

24. See Pomerantz, Pristach and Carson [20].

25. T.A. Ryan and C. Schwartz, "Speed of Percep- tion as a Function of Mode of Representation," American Journal of Psychology 69 (1965) pp. 60-69.

26. J. Hochberg, "Art and Perception," in E. Carterette and M. Friedman, eds., Handbook of Per- ception, Vol. 10 (New York: Academic Press, 1978) pp. 225-258.

27. S. Pinker, "Visual Cognition: An Introduction," Cognition 18 (1984) pp. 1-63.

28. M.A. Peterson and B.S. Gibson, "Object Recog- nition Contributions to Figure-Ground Organiza- tion: Operations on Outlines and Subjective Con- tours," Perception & Psychophysics 56, No. 5, 551-564 (1994).

Dorothy Washburn is an archaeologist who studies the kinds offeatures ofform used in category formation. Her research centers on the property of symmetry and how symmetrical patterns embody cultural information.

Manuscript received 19January 1999.

202 Washburn: An Interactive Test of Color and Contour Perception



an interactive test of color and contour perception by artists and non-artists

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