Color naming and hue discrimination in congenital tritanopia and tritanomaly

Color naming and hue discrimination in congenital tritanopia and tritanomaly

Vkion Res. Vol. 13, pp. 209-218. Pagamon Press 1973. Printed in Great Britain. COLOR NAMING AND HUE DISCRIMINATION IN CONGENITAL TRITANOPIA AND TRIT...

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Vkion Res. Vol. 13, pp. 209-218. Pagamon

Press 1973. Printed in Great Britain.

COLOR NAMING AND HUE DISCRIMINATION IN CONGENITAL TRITANOPIA AND TRITANOMALY DAMIENP. SMITH VictorianCollegeof Optometry,Universityof Melbourne,374 CardiganStreet,Carlton3053,Australia

(Receioed10 July1972)

THE ABILITYto name colors requires a physiological process for receiving color information and transmitting it to the brain, and a culturally dependent, learned hue-word association. Hue discrimination is an essential factor in color-naming ability, and the hue discrimination function of color normals is contained in and can be derived from their color-naming data (SMITH, 1971). The situation in dichromasy should be similar, except that our understanding of its origins and our knowledge of the modified dichromatic hue discrimination function lead us to predict that the color-naming performance of dichromats should be in terms of only two hues. Protanopes and deuteranopes lack either erythrolabe or chlorolabe respectively (RUSHTON, 1966) and their remaining chromatic process should signal only blue and yellow. Studies of unilateral dichromasy suggest that this is so; blue and yellow were the colors seen by the dichromatic eye in terms of the color perception of the other eye. While compelling, this evidence is not unequivocal. Herman Goldenberg, originally described by HOLMGREN(1880) as a unilateral protanope may have been a deuteranope (WALU, 1958), and the other eye of the unilateral deuteranope reported by SLOANand WOLLACH(1948) was deuteranomalous. The subject of GRAHAMand HSIA (1958) had an irregular unilateral deuteranopia that was possibly acquired (Cox, 1961); in fact she failed several blue-yellow plates on the AOHRR test (WALLS, 1959) as do acquired red-green defectives. The dichromat is believed to discriminate within his two basic hue sensations on the basis of saturation and luminosity differences, such cues enabling the application of several color names to variations within the one hue. However, using an experimental procedure that eliminated luminosity differences, SCHJZIBNER and BOYNTON(1968) found that red-green dichromats color named in a manner dependent upon wavelength in the supposedly isochromatic spectral zone of wavelengths longer than 530 nm where all wavelengths should appear of the same color to protanopes and deuteranopes. Scheibner and Boynton postulated the presence of a residual red-green system in these dichromats to explain their apparent perception of variable hue at long wavelengths. The tritanope presumably lacks cyanolabe, and his remaining chromatic process should signal only red and green so that “the tritanope sees only two hues (red and green) in the spectrum. . . ” (BURNHAM,HANES and BARTLESON,1963) and “. . . will not find in his spectrum any such hybrids as orange and green-yellow or blue-green and purple.” (LINKSZ, 1964). The two hue theory is supported by the study of GRAHAM, HSIA and STEPHAN(1967) reporting a unilateral acquired tritanope. He placed his homochromes at about 478 nm and 617 mu 209 V.R.13/2-A

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and related that generally colors seen by the tritanopic eye were bluer and less yellow than those seen by the normal eye. The appearance of the spectrum to bilateral congenital tritanopes has also been described. The tritanope reported by JUDD, PLAZA and FARNSWORTH (1950) when presented with the entire spectrum, set 585 nm as the point above which the spectrum appeared red or reddish and below which it appeared blue or green. WRIGHT (1952) presented the wavelengths 420 nm and 530 nm in a bipartite field and found his tritanopes called the field either blue or green. COLE (1965), without equating the stimuli for luminance, presented tritans with spectral wavelengths in ascending consecutive order and allowed any color name e.g. grapefruit, to be used by the subject. His results showed the expected tendency, tritanopes saw blue or greenish hues below their neutral zone and reddish hues above it, with tritanomals responding similarly but employing names more suggestive of yellow. WALLS (1964) investigated the color naming of three typical congenital tritanopes with both spectral stimuli and Munsell color chips. He randomized the order of presentation of the colors, but did not eliminate brightness differences. The three tritanopes named colors in a virtually normal manner, employing either five or six hue names and appropriate hybrids of these. Their performance was surprisingly good, and certainly far superior to that of the other tritanopes reported. Walls did not offer any serious explanation of this apparent multiplicity of perceived hues in the subjective spectrum of tritanopes. SCHMIDT(1970) briefly mentioned the color naming of two tritanomals. One of these was presented with monochromatic lights in randomized order and the color names given to the different wavelengths “recall those used by WALLStritanopes (1964)“. The well-validated color-naming procedure that originated with BOYNTON,SCHAFERand NEUN (1964) and was employed by SCHEIBNERand BOYNTON(1968) in their study of protanopes and deuteranopes has not been applied to congenital tritanopes, although variations of it have been used on subjects with normal color vision exposed to stimulus conditions which produce fovea1 tritanopia [KAAUSKOPPand SREBRO(1965); WEITZMAN and KINNEY(1967, 1969); KAISER(1968); INGLING, SCHE~BNER and BOYNTON(1970)]. In none of these studies, however, has color-naming been classically dichromatic, that is with the spectrum reduced to two hues, green and red, seen below and above respectively a white zone in the yellow region of the spectrum. The tendency is certainly tritanopic; the color name white replaces yellow, and blue and green are confused. Krauskopf and Srebro stated that the “blue” and “green” judgements which occur below the neutral zone result from “activation of neural units with identical spectral sensitivities” and Ingling et al. felt that the “blue” and “green” responses in that spectral region “carry the same information”. The present study was undertaken when one tritanope and two tritanomals became available, briefly, for investigation. The study had three objectives; (1) to determine the subjective appearance of the spectrum of the tritans using a standardized color-naming technique, (2) to test for displacement along the spectrum of the individual color name curves of tritanomals, which does occur in deuteranomaly and protanomaly (RUBIN, 1961), and should occur iftritanomaly represents a distortion of the blue spectral sensitivity function, and (3) to derive hue ~sc~~nation measures for these tritans according to the method of SMITH(1971). The limited availability of the tritan subjects restricted the breadth of the investigation to that described here.

Color Naming and Hue Discrimination

in Congenital Tritanopia

and Tritanomaly

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SUBJECTS

who acted as subjects have been previously reported. NB was III 8 in the pedigree of HENRY, COLE and NATHAN(1964) and COLE, HENRY and NATHAN(1966), and NB in the study of COLEand WATKINS (1967). Her daughter RB was IV 6 in the Henry et al., Cole et al. pedigree. The tritanope RP is not related to the other two tritans and was RP in the Cole and Watkins study. Their tritan defect was con&rued clinically by the AOHRR and Farnsworth F2 pseudoisochromatic plates, and the Farnsworth-Munsell lOO-hue, 28 hue and Panel D-15 tests. NB and RB were classified as tritanomals when they were unable to match spectral light of 530 nm with a mixture of red (h dom = 650 nm} and blue (X dom = 452 run) light and could not find a spectral match to white lights of color temperature 6500°K and 2854°K. As reported by Cole and Watkins, RP was shown to be dichromatic when he successfully matched 530 nm with a mixture of red and blue light. Clinical examination showed that all three tritans had monocular visual acuities of 6/4*5 or better, normal central visual fields and Noel-loo~ng optic discs. Ten subjects with visual acuity of 616 or better and normal color vision made observations on the same color-naming apparatus to provide control data. The three

tritans

APPARATUS

AND

PROCEDURE

Monochromatic test stimuli from 400 to 650 nm in IO-nm steps were presented randomly in a 2” circular fieid seen in Maxwellian view by the undilated pupil. The stimuli, derived from a Hi&r grating monochromator with a ~nd~dth of 9 nm were each presented three times. A manuallyoperated photogmphic shutter maintained stimulus duration at 364 msec (u = 7 msec). The spectral stimuli above 450 nm were equated for luminance by heterochromatic matching, and had a luminance of 8.1 cd rnm2. Stimuli below 460 nm were not of equal luminance and luminance fell to l-55 cd m-’ at 400 nm. A calibrated neutral density wedge inserted in the test beam provided intensity control. The same wedge settings established by normal observers for each wavelength were used for both normals and tritans on the basis that the tritan luminosity curve does not differ appreciably from the normal (WRIGHT, 1952; SCHMIDT, 1970). The test fietd was viewed in the centre of a white surround of hmtinance 8-21 cd mez. The subject’s head was held in a chin and forehead rest with temple clamps. Only the right eye of each of the normals was studied. Both eyes of each of the tritans were studied, the eye not under investigation being occluded. The subject’s response was limited to one of the following color names-blue, green, yellow, red or white. or any hybrid of these. Responses were scored according to the method of B~YNTON and GORDON (1965), with a maximum score of three points for a single hue response, and two points for the major and one point for the minor component in a hybrid name response. For the hue domination derivation, indices of nameable color difference (I.N.C.D.) were obtained by computing lO/ASh where ASA is the sum of the differences between the ~lor-na~ng scores at adjacent wavelengths (SMITH, 1971).

RESULTS

Color naming The individual color-na~ng functions of the tritans are presented in Figs. 1 and 2 together with the summed color-naming function of the normal observers, The subjective spectrum of tritans was found to be multihued; they named the spectrum in terms of violet, blue, green or blue-green, yellow and red. The red and yellow name curves were very similar to normal, and blue-red (violet) was always called at short wavelengths. The blue and green color name curves suffered the greatest deviation from the normal response. There was little or no desaturation of the spectrum, even in the yellow. The tritanomals each had one eye which gave a virtuahy normal color naming response. RP. The tritanope, RP, gave almost identical responses with each eye. His red and yellow name curves are normal, but his blue-red or violet response is reduced in amplitude and spectral extent. He called blue from 400 to 560 nm, and blue replaced green almost

DAWN P. St+ur~

212

10r

WAVELEMGN,

mm

FIG. 1. Color-namingfunctions. Top, sum of 10 normal observers: middle, tritanope RP, right eye: bottom, RP, left eye. Legend: l blue, 0 green, 0 yellow, II red and v white (-).

completely in the middle spectrum for his right eye. The appearance of green at very short wavelengths may have an explanation. RP commented that he differentiated blue from green on the basis of brightness, with green appearing the darker color. The luminance of the spectral stimuli fell markedly for those below 460 nm, so it is possible that RP called green at those wavelengths because they were photometrically duller. However, he could not have differentiated green on brightness difference in the middle spectrum with his left eye. Surprisingly, RP did not use the response white at all. When questioned on this, he gave the expected answer that yellow had a lot of white in it, as did some of the “sky-blue” colors. However, he did not regard white as a significant component in any of the spectral stimuli. NB. The tritanomal NB named colors normally with her right eye, except that “‘blue” was called as a hue component for wavelengths longer than 600 nm. In her left eye the blue-red

Color Naming and Hue Discrimination in Congenital Tritanopia and T&anomaly

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lo

0

b

1

2

0 MO

003 WAVELENGTH,

boo

boo

so

nm

Frc. 2. Color-naming functions. Top, tritanomal NB, right eye: upper, NB, left eye: lower, tritanomal RB, right eye: bottom, RB, left eye. Legend: e blue, 0 green, 0 yellow, B red and v white (-1.

(violet) response was depressed and narrowed; green replaced blue at short wavelengths and blue replaced green in the middle spectrum. RB. The tritanomal RB gave a normal color naming response in the left eye except for a slight broadening of the green curve. In her right eye, blue partially replaced green in the middle spectrum, and the yellow name curve was displaced 10 nm toward the red. RB called 570 nm white on every presentation although she has no neutral point at that wavelength by matching tests. After her right eye was tested she commented “when I didn’t know what

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the color was I called it blue”. The stimuli when seen by her left eye were “like a different set of colors”. The tritanope was not clearly differentiated from the tritanomals by his color naming performance. His blue-red (violet) response appears smaller than that of the tritanomals, while his yellow response reaches further towards the short wavelengths. The tritanomals did not exhibit any displacement of their color-name curves as might be expected if their anomalous trichromacy represents an alteration system. Hue discrimination

Indices of Nameable Color Difference (I.N.C.D.) were calculated according to the method of SMITH(1971), employing in this case the arbitrary arithmetic adjustment IO/Ash to derive the threshold. Figure 3 represents the hue discrimination curves as T.N.C.D.

6.0

6.0

F

6.0

0 400

-A 450

500 WAVELENGTH,

5.50

600

660

nm

FIG. 3. Wavelength discrimination, I.N.C.D. values and AX thresholds. Top: 0, I.N.C.D., sum of 10 normal observers; v, AAthresholds, tritanope A, WRIGHT(1952). Middle: I.N.C.D., tritanope RP, 0 right eye, n left eye. Bottom: I.N.C.D., tritanomals NB, 0 left eye and RB, A right eye; 0 tritanomal F.F., SCHMIDT(1970).

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against wavelength for both eyes of RP and for NB (left eye) and RB (right eye). Included for comparison are the I.N.C.D. curve of the ten normal observers, and the Ah against X curves for the tritanope A of WRIGHT (1952) and the tritanomal F.F. of SCHIMDT(1970). The I.N.C.D. curve of the normals demonstrates the expected minima in the blue, blue-green and orange, and reinforces the earlier finding (SMITH, 1971) that variation of color naming response is an accurate reflection of hue discrimination. The I.N.C.D. curve in Fig. 3 does not show the anomalous maximum at 520 run that was present in the previously reported (SMITH, 1971) I.N.C.D. curve of normals, due probably to the different group of observers and different experimental conditions. The I.N.C.D. curves of the tritans lack the normals minimum in the blue-green and show good discrimination in the violet and yellow spectral regions with decreasing discrimination into the red. The shape of the tritan I.N.C.D. curve is as expected, except that the discontinuity in the long wavelength blue and blue-green is considerably broader than that in the wavelength discrimination curves of tritans found by j.n.d. techniques. The discontinuity at 540 nm in the I.N.C.D. curve of RP (right eye) reflects his use of the color-name blue-yellow between 530 and 550 nm. The maximum in the I.N.C.D. curve of NB (left eye) at 580 nm reflects her successive use of the color-name yellow at 580-590 nm.

DISCUSSION The Mans

in this experiment behaved like those of WALLS (1964) and named their subjective spectrum with a number of hue names. They also showed the same degree of inter- and intra-subj~t variation in their responses. It is of course impossible to know just what hue is actually seen by a color defective when he attaches a color name to a particular wavelength stimulus. Nevertheless, it is a reasonable assumption that when a color defective uses two or more color names and applies them in a discriminatory manner he is perceiving two or more different sensations, whatever color they may in fact appear to him. Different sensations does not necessarily imply different hues, especially in tritanopia where the use of a multiplicity of color names is suggested by the elaborate wavelength discrimination curve. Tritanopic confusion lines converge to the blue corner of the chromatic&y diagram where they cross the spectral locus close together (THOMSONand WRIGHT, 1953), providing excellent wavelength discrimination in that area. Several color names should be employed to describe spectral stimuli from that violet area. The tritanope has poor wavelength discrimination in his isochromatic zone between violet and green-blue, entailing the use of a single color name to describe that portion of the spectrum. Through the green and green-yellow to the neutral point is increasingly desaturated, and several color names should describe this change. The immediate long wavelen~ side of the neutral point is also desaturated, but decreasingly so into the red. The tritanope should use differences in color name to describe this change in saturation before adopting a single color name to describe the long wavelength spectrum. The areas of desaturation about the neutral point correspond with good wavelength di~~ination. Clearly, good color-naming is to be expected of tritanopes, and in general the tritanope RP color-named in the expected manner. He used several color names in the violet, called only blue through his isochromatic zone, introduced green and yellow to describe the saturation changes about the neutral area, and called only red into the long-wavelen~h spectrum. The sharply discriminatory manner in which the color name yellow was used in

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the correct spectral region might suggest that it represents, as it does in normals, a hybrid hue resulting from the synthesis of red and green. Alternatively, an argument can be made that the apparent perception of yellow is merely the misuse of the name yellow to describe a neutral or white perception. The latter argument is supported by the fact that tritanopes will often call the matched field of white to the spectral stimulus that defines their neutral point as yellow, yellow-green or even light brown. However, RB (right eye), an incomplete tritanope, clearly differentiated the neutral stimulus white at 570 mn from the yellow color she reported at 590-600 nm. The yellow name response of the other tritans also peaked at or longer than 580 mn. Furthermore, as W~LS (1955,1964) points out, while the tri~nopic neutral zone (to Illuminant B) occurs at about 570 nm the minimum in the tritanopic hue discrimination curve occurs at 590 nm, a point called yellow by normals as well as tritans. Perhaps, if the neutral zone in tritanopia is the point of maximum desaturation, reflecting the intersection point of two fundamental response curves, the yellow color-naming response reflects the spectral area where the gradient of desaturation change is steepest. The data of COLE eb d. (1966) indicates that the rate of change of purity threshold is indeed highest at the immediate long wavelength side of the neutral point. Yellow must therefore be the name applied to the rapid change of saturation level of the hue red, andin no way represents hybrid hue or a neutral perception. The gradient of saturation change on the other, short wavelength side of the neutral point is apparently insufficient to generate a perception change that can be so dramatically described by change of color name. As can be predicted, good color-naming occurs in tritanopia, and certainly it is not necessary to hypothesize such possibilities as residual cones of the type supposedly missing to explain it. Of interest is the report of bluishness at wavelengths longer than 600 nm by the almost normal right eye of NB. The atypical t&nope SK who puzzled Walls in 1964 also reported the appearance of bluishness in the red region of the spectrum. Walls co~ented that the perception of bluishness beyond 600 nm is inexplicable for a normal observer, never mind for a tritanope whose blueness receptors are supposedly missing. However the purple spectral locus bounds a confusion area for tritanopes, and the report of bluishness in a red stimulus is not that unexpected, especially in an incomplete tritanope like NB. Like Walls’ tritanopes, the tritanope in this study did not employ the name white, even around his neutral point, although the incomplete tritanopes tended to. A possible explanation might be that dichromats do not see whiteness or desaturation as “spoiling” a color as normals do, but see it instead as an integral part of the color itself. That is, because dichromats use saturation levels as a cue in almost every color they perceive, they might be unable to separate the desaturant whiteness from the color, because to them that whiteness is innate to the color. Incomplete tritanopes presumably rely less on saturation as a cue, and are therefore able to differentiate, to some degree, desaturant whiteness from hue itself. Such an explanation is consistent with the findings of this color-naming study. The inability to appreciate desaturation and the comparatively reduced red response in the violet are the only distinct differences between the color-naming of the tritanope and the tritanomals, although the subject numbers are too small and responses too variable to delineate significant differences. The tritanomals showed no appreciable shift of the loci of spectral hues along the spectrum in the way RUBIN(1961) has shown they do in red-green anomalous trichromacy; this is further evidence that tritanomaly is better termed incomplete tritanopia, the result of a partial reduction rather than an alteration system. This study demonstrates that the

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relatively elaborate hue discrimination curve of tritans is reflected in their ability to subjectively differentiate the spectrum by name. However, they may still see the spectrum in terms of only two hues, red and green (usually called “blue”), identifying two other areas

as “green”and “yellow” by saturation changeinthegreenand red hues. The I.N.C.D. curves derived from the color naming of the normals and the tritans accurately represent the hue discrimination of those observers as measured by traditional wavelength difference methods, strong argument for the validity of the derivation technique. The manner in which the tritan I.N.C.D. curves qualitatively parallel the tritan wavelength discrimination curves measured by WRIGH-I (1952) suggest that the derivation of hue discrimination from colornaming can be a useful diagnostic tool in dyschromatopsia.

BOWON,

REFERENCES R. M. and GORDON, J. (1965). Bezold-Brucke hue shift measured by colour-naming technique.

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R. M., SCHAFER,W. and Nm, M. E. (1964). Hue-wavelength relation measured by colournaming method for three retinal locations. Science, N. Y. 146,666668. Bm, R. W., HANES,R. M. and BARTLEION,G. J. (1963). Colour: A Guide to Rasic Facts and Concepts. Wiley, London. COLE,B. L. (1965). Characteristics of tritanopia. Thesis. University of Melbourne. COLE,B. L., HENRY,G. H. and NA’IIIAN,J. (1966). Phenotypical variations of tritanopia. Vision Res. 6, 301-313. COLE, B.

L. and WATKINS, R. D. (1967). In crement thresholds in tritanopia. Vision Res. 7,939947. Cox, J. (1961). Unilateral colour deticiency, congenital and acquired. J. opt. Sot. Am. 51,992-999. GRAHAM,C. H. and Hsu, Y. (1958). Colour defect and colour theory. Science, N. Y. 127,675-682. GRAHAM,C. H., Hsu, Y. and Sv, F. F. (1967). Visual discriminations of a subject with acquired unilateral tritanopia. Vision Res. 6 469-479. HENRY, G. H., COLE,B. L. and NATHAN,J. (1964). The inheritance of congenital tritanopia with the report of an extensive pedigree. Ann. hum. Genet. 27,219-231. HOLMGREN, F. (1880). Ueber die subjective farbenempfindung der farbenblinden. Centralbl. f: med. Wiss. 18,898-900.913-916. INGLING, C.

R., SCHEIBNER, H. M. 0. and BOYNTON, R. M. (1970). Colour naming of small fovea1 fields.

Vision Res. 10, 501-511.

JUDD,D. B., PLAZA,L. and FARNSWOR~B, D. (1950). Tritanopia with abnormally heavy ocular pigmentation. J. opt. Sot. Am. 40,833-841. msmc, P. K. (1968). Colour names of very small fields varying in duration and luminance. J. opt. Sot. Am. 58, 849-852. KRAUSKOPF,J.

and SREBRO, R. (1965). Spectral sensitivity of colour mechanisms: derivation from fluctuations of colour appearance near threshold. Science, N. Y. 150, 1477-1479. LINKSZ,A. (1964). An Essay on Colour Vision and Clinical Cotbur-vision Tests, p. 122. Gnme h Stratton, New York. Ru~I~N,M. L. (1961). Spectra1 hue loci of normal and anomalous trichromats. Am. J. Ophthul. 52,166-172. RUSH~>N,W. A. H. (1966). Densitometry of pigments in rods and cones of normal and colour defective subjects. Znvestve. Ophthal. 5233-241. SCHEIBNER, H. M. 0. and BOWON, R. M. (1968). Residual red-green discrimination in dichromats. J. opt. Sot. Am. 58,1151-1158. SCHMIDT,1. (1970). On congenital tritanomaly. Vision Res. 10,717-743. SLOAN. L. L. and WOLLACH. L. (1948). A case of unilateral deuteranooia. J. out. Sot. Am. 38. 502-509. Sr.nr~,. D. P. (1971). Derivation’of wavelength discrimination from colour-n&ning data. Vision Res. 11, 739-742. THOMSON, L. D. and WRIGIFT,W. D. (1953). The convergence of the tritanopic confusion loci and the derivation of fundamental response functions. J. opt. Sot. Am. 43, 890-894. WALLS,G. L. (1955). A branched-pathway schema for the color vision system and some of the evidence for it. Am. J. Ophthal. 39. No, 2. pt. 11. 8-23. WALLS,G. L. (1958). Graham’s theory of dolour blindness. Am. J. Optom. 35,449-X0. WALLS.G. L. (1959). Peculiar colour blindness in neculiar neonle. A.M.A. Archs. Oohthal. 62. 13-32. WALLS;G. L. (1964). Notes on four tritanopes. Vision Res.-4,3-16. WEITZMAN, D. 0. and KINNEY, J. A. S. (1967). Appearance of color for small, brief, spectra1 stimuli, in the central fovea. J. opt. Sot. Am. 57,665-670.

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WEITZMAN,D. 0. and KINNEY, J. A. S. (1969). Effect of stimulus size, duration and retinal location upon the appearance of colour. J. opt. Sot. Am. 59,64&643. WRIGHT, W. D. (1952). The characteristics of tritanopia. J. opt. Sot. Am. 42, 509-521.

Abstract-The color naming performance of one congenital tritanope and two congenital tritanomals was investigated. They were required to apply one or more of the names blue, green, yellow, red and white to spectral stimuli (400-650 nm) exposed for 364 msec. They employed all four color names with the use of blue and green being most different from normal. The tritans did not report the spectrum as markedly desaturated, even in the yellow. Index of Nameable Color Difference (I.N.C.D.) curves derived from the color-naming data closely resemble the tritan wavelength discrimination function measured elsewhere by traditional wavelength difference methods.

R&urn&--On Ctudie chez un tritanope congenital et chez deux tritanomaux congenitaux les resultats pour nommer les couleurs. 11sdevaient appliquer un ou plusieurs des noms bleu, vert, jaune, rouge et blanc ti des stimuli spectraux (400 % 650 nm) exposes pendant 364 ms. 11s emploient tous les quatre noms de couleurs, t’utilisation de bleuet de vert &ant la plus differente de la normale. Les tritans ne dtSsignent pas le spectre comme nettement dtsature, miZme dam ie jaune. Les courbes d’Index des Noms de Couleurs Differentiels (I.N.C.D.) d&iv&s de ces experiences rappellent la fonction de discrimination en longueurs d’onde mesun& autre part chez les tritans par les mtthodes traditionnelles de differences de longueurs d’onde. Zu~rn~~~-~ wurde das F~~n~ne~u~sverm6gen von einem von Geburt an Tritanopen und zwei von Geburt an Tritanomalen untersucht. Sie sollten die Rezeichnungen blau, grtln, gelb, rot und weil3 auf fiir 364 ms angebotene spektrale Reize (400-650 nm) anwenden. Sie verwendeten alle vier Farbbezeichnungen, wobei blau und griin am staksten vom Normalen abweichend benutzt wurden. Kurven, die den Unterschiedsindex des Farbenbenennbarkeitsvermogens beschreiben (I.N.C.D.), und die von den Farbbenennungsdaten abgeleitet wurden, Bhneln stark den Farbunterschiedskurven von Tritanopen, die an anderer Stelle mit t~ditionellen WeIlenl~~en-Unte~~edsmethod~ gemessen wurden. Pesmw+-EbLna riccnenonana cnoco6nocrb ria’JbrBarb uaera OAHUMHa6snonareneM c spoxAemIoft TpsiTaHomiett B AayMa HaGnroAaTenahfx c apoxwemioti rp5irawoMamie2t. WI npeAnaranocb HCIIOA~~OB~T~ oAno HJIH 6one-e ~3 ~a.%am& UB~TOB: cmisii& 3enewil, z%enTbI#, xpacnbrtt R 6em&-no ortiomeiimo K cnexrpa.nbrrbtM c%fMynaM (400-650 HM), npenansnlieMbIM Ha 364 MCkXC. &IH HCIIOAb3OKiJIH BCe 4 HaaBaHHa uBeTOB,iIpEiYeM CHHS~ U 3eJleffbIB uan6onee macro ormnawcb OT HophSI.&% ~~HoM~bI He xa~~epH3o~n~ CneKTp saMeMoneHacMme~M,A~e3~~bIXn~ax. KpHBble Index of Nameable Color Difference (I.N.C.D.), nonylreHHbIe Ha OCHOB~ namibtx nOHa3BanrtH,~BeTOB,~bMa~OAHMC~yHI(UHe~UBeTOpa3nHYeHWR TpHTaHOIIOBHTp~TaHOManoB,onpe~enemio~ panee o6blwrbIhw MeToAahm pa3nwieHHa cneRpanbHbIx H3nyremik