Perception, 1986, volume 15, pages 657- 666

Walter Stanley Stiles 1901 - l985

Stanley Stiles (as he liked to be known) was born on 15 June 1901 and died on 15 December 1985. He was one of the most distinguished visual scientists of our century.

Stiles was educated at the Polytechnic Secondary School, Regent Street, London. He entered University College London, with an Andrew Scholarship in 1918 and graduated in physics in 1920. After continuing at University College for two years as a Demonstrator under Sir William Bragg, he spent the year 1922- 1923 reading mathematics at St John's College, Cambridge. He joined the National Physical Labora- tory in 1925, and-though often tempted to move when promotion was slow during the nineteen forties-remained there until his retirement in 1961. He was created OBE in 1946 for his wartime work on visibility, visual search, and the defensive use of dazzle. He was elected to the Royal Society in 1957, and was awarded the Tillyer Medal of the Optical Society of America in 1965. He served as General Secretary of the Commission Internationale de l'ficlairage from l928 to 193 1, was Chairman of the Colour Group of Great Britain from 1949 to 1951, and was President of the Illuminating Engineering Society from 1960 to l 96 1.

Above all, Stiles was a great psychophysicist. G Brindley, when introducing in his textbook the distinction between Class A and Class B observations, took Stiles as the prototype of those psychophysicists who base their arguments only on Class A observations, that is, on matches and thresholds. In his published work Stiles almost always eschewed Class B observations, in which the subject must describe the quality or intensity of his sensations. In his Foreword to Pirenne's Vision and the Eye (1948) he applauds the author for "the avoidance of arguments founded on introspective descriptions of sensations, which are notoriously difficult to interpret correctly". His psychophysical doctrine is well captured in an exchange with Dr R Hunt that has been preserved for us by the editors of the Helmholtz Memorial Symposium held at Driebergen [J J Vos, L F C Friele, and P Walraven, 1972 Color Metrics (Soesterberg: Institute for Perception TNO), page 118)l:

"Hunt: I think Dr Stiles should explain how he can study colours and dispense with sensations.

Stiles: You put a man down behind a colorimeter, you guide his hand to three knobs and let him go ahead.

Hunt: This tells you everything?

Stiles: Of course not. But you ask him to make certain settings based on the appearance of the colorimeter field. You draw your conclusions from the relations between the stimuli exposed in the fields, and the settings he makes. In expressing these relations it is not necessary to claim one is 'measuring a sensation' or in fact to 'regard a sensation' as having any particular meaning as scientific term. Of course, the word 'sensation' may be used colloquially to explain to the observer what you want him to do."

In his own experimental work, Stiles showed us how powerful could be the conclusions drawn from a structured set of Class A observations. In the increment-threshold technique, novel when he introduced it in 1929 but now part of the standard armoury of psychophysics, a brief test flash serves as a probe to determine the sensitivity of the retina at a particular point in time and space. An important variant of the technique was

his two-colour method, in which a monochromatic increment is delivered on a mono- chromatic field. This method has been widely used to test the presence and sensitivity of individual classes of receptor in normal and abnormal vision.

But the most important of Stiles's contributions to visual psychophysics was the model that lay behind his use of the two-colour method. His concept of a 'mechanism' has subsequently been extended to other sensory dimensions, such as spatial frequency, and it is now commonplace in visual science to test for the existence of 'channels' that are independent in adaptation and in detection. Pamela Fowler, who worked as Stiles's assistant from 1947 until his retirement, recalls above all his reluctance ever to discard an anomalous reading: however aberrant a data point might seem at the time, there had to be a reason for the aberration and the anomaly might later prove significant. Stiles was always the first to point out departures of his own data from his model. These scruples were rewarded. For many anomalies and minor inflexions in Stiles's early increment-threshold results have since turned out to be important phenomena in their own right.

Among the other scientific achievements for which Stiles will be remembered are his discovery, with B H Crawford, of the directional selectivity of the cones, and the change in colour of monochromatic lights when the point of pupil entry is displaced; his concept of the 'equivalent background'; his discovery, with M Aguilar, that the rods saturate at photopic levels; his line-element analyses of colour discrimination; his demonstration, with R M Boynton and M Ikeda, of inhibitory interactions between test flashes of different wavelength-perhaps the first use of Class A experiments to demonstrate opponent processes; and his measurements, with J M Burch, of the large- field colour matches of over fifty observers, measurements that served as the main basis for the CIE 10-deg standard adopted in 1964.

Intermittently from 1928 onwards, and more systematically after 1944, Stiles kept a series of notebooks that constitute an intellectual and scientific journal('). Pamela Fowler vividly remembers the ever-present pot of paste kept on his desk for the purpose of sticking jottings, cuttings and correspondence into the notebooks. In his lifetime the notebooks became a legend, and internal detail indicates that he intended them to survive him. R A Weale [ l986 Nature (London), 319 6231 has described how, during the war, Stiles would amass the notebooks under his arm whenever air-raid sirens sounded. There is indeed much in the notebooks that was published only long afterwards or was never published at all. Here are a few examples: (i) March 1932. Notes on the relationship between the number of quanta absorbed at absolute threshold and the slope of the psychometric function. (Initially Stiles had the mistaken idea that the slope would depend on the wavelength; but this error was corrected by 1934.) (ii) March 1945. Increment-threshold measurements on a cone monochromat. For the condition X = 480 nm, p = 600 nm, at high field intensities, there appeared to be two distinct thresholds for the short-wave test flash, a lower one where it was visible as a patch darker than the field and an upper one where it was visible as a patch brighter than the field; in the interval, the target was of "equal density with the field". (iii) January 1947. First proposal for a test-additivity experiment. Targets of 490 and 690 nm would be used to isolate the rods and cones respectively and a weak blue-green background would be added "to knock out with certainty rod vision of A = 690".

The notebooks, with their many tables, provided a basis for Color Science (1967, 1982), which Stiles wrote in collaboration with Giinter Wyszecki and which will long

( l) After his death, Mrs Stiles deposited the notebooks, and other papers, with the Archive Room of the Cambridge Psychological Laboratory. The material is registered with the National Registry of Archives and can be examined on prior application to the Librarian, Department of Experimental Psychology, Downing Street, Cambridge.

Walter Stanley Stiles 1901 - 1985 659

remain a definitive handbook in the field. Wyszecki was one of Stiles's closest friends, and at the time of his own death, Stiles was at work on a memoir of Wyszecki. The friendship between Stiles and William Rushton-although its public legacy was less tangible-was also critical in the development of visual theory. From Stiles, Rushton drew the Principle of Univariance, which is explicit but unnamed in Stiles's "Spectacle makers" paper of 1948 and which provided the bedrock for so many of Rushton's experiments. And it was Rushton, during the 1960s, who did much to draw attention to Stiles's obscurely-published papers on ^-mechanisms. The esteem in which these two visual scientists held each other is witnessed by the many letters from Rushton that Stiles has pasted into his notebooks, sometimes beside his draft reply.

If a man is to be remembered by his friends, then it is proper that his rivals too should be recorded. There was one rival who did bother Stiles, and that was the brilliant Dutch physicist, Hessel de Vries. During the 1940s, de Vries independently worked on issues and methods that were close to those that concerned Stiles: the quantum nature of vision, the effect of temperature on sensitivity to long-wave light, the derivation of cone sensitivities by the two-colour method, Weber fractions and the line- element, the anomalies of the blue mechanism. Two of the devices that became part of the modern Stilesian canon-the auxiliary field and the field-additivity test-were first introduced by de Vries. It must indeed have been disturbing to Stiles to hear so many of his own ideas elliptically expressed in the paper that de Vries gave to the Optical Con- gress in Paris in 1946. In later years Stiles always changed the topic when de Vries was introduced into conversation, but in his final retrospective essay (printed in this issue of Perception) he acknowledges both the cleverness of de Vries and the discomfort he felt about him.

During the war, as a result of his service on the Vision Committee, Stiles came to know Kenneth Craik. When Craik was killed in a road accident on the eve of VE Day, Stiles was prompted to a characteristic note in his journal, a note that we are surely intended to read and one that says something about both men:

"10.5.45. Learnt today that K. J. W. Craik was knocked down and killed in a road accident in K. P. [King's Parade] Cambridge. Craik had an active, brilliant mind and unlimited energy. Much of his war work has been necessarily of rather sketchy and slapdash character but he would in all probability have produced work of the finest quality in psychology had he lived. Personally, Craik was most likeable and he seemed to take no pleasure in the gossip and backchat against persons which has unfortunately played a part in the Vision Cttee's activities. We got on well enough, although I felt sometimes that he maintained to me a reserve not apparent in his relations with the younger men (Goldie, Robertson etc). Perhaps I fell short of his high standards or possibly, being human, he felt that our lines of work were so close that he and I must necessarily be rivals despite the great difference of age. He is a loss to science."

Owing to his mathematical prowess, his reserved nature, and the uncompromising precision that he brought to scientific argument, Stiles was a formidable figure for many visual scientists. From his assistants he expected a formal manner of address. But he showed himself a man of great kindness in the guidance and tactful encouragement he gave to younger workers. On public occasions, he enjoyed the rare talent of being able to express exactly the right sentiment with exactly the right words. He shared 57 years of marriage with his wife, Pauline ('Polly'), the daughter of Judge Henrik Brendstrup, of Hillerod, Denmark. Polly herself died on 6 April 1987.

Although he was celebrated for avoiding subjective description in his scientific work on colour, Stiles privately delighted in the richness of our internal palette. Occasionally he did allow himself to record the appearances of the stimuli in his colorimeter (see the paper by Pugh and Kirk in this issue, and plate l ) , and in his retirement he became an accomplished amateur painter. During his working life, however, he had little taste for

conventional hobbies or sports. He enjoyed holidays spent with his father at Groombridge in Sussex, and with Polly's family in Denmark. But his main recreations were cerebral. He read widely in modern history, literature and philosophy, admiring Pope, H G Wells, Trollope, Galsworthy, and Eddington. He was a member of the British Psychological Society and records listening to papers by Burt, Thouless, and Eysenck at the Oxford meeting of 1943.

Above all, it was with mathematics that Stiles occupied his spare hours, filling many ledgers with notes. In his wartime journal he wrote:

'Repairs to binding of Caratheodory's 'Real Functions' and Hardy's 'Pure Maths', two books the study of which has given me more pleasure than any other works of science."

He had left Cambridge prematurely in 1923 after securing only a second class in Part I of the Mathematics Tripos. This always rankled with him, and passages in his notebooks reveal his recurrent doubt as to whether he should leave the backwater of visual science and pursue a career in mathematics or theoretical physics. In July 1944 he wrote of our field:

"The phenomena are so numerous and apparently incoherent and the difficulties of reproducing results are so great that the interest of any theory can be only very limited. The unreal' world of pure mathematics is so much better behaved. Researches on vision entail a lot of hack work-an enormous pudding of rather unsatisfactory observation with one small plum of scientific interest."

But, on this occasion as on others, the doubts passed: by October of 1944 he could write

"Back at work on threshold apparatus. Something of a thrill again to probing the mysteries of retina1 sensitivity"

and by Christmas (despite the night-time distraction of flying bombs and his daytime duties as Chairman of the Goggles Subcommittee) he had established the variation of the cone sensitivities across the fovea, the low acuity of the short-wave mechanism, the slow adaptation of that mechanism to long-wave fields, and the variation between observers in its sensitivity.

Any complete account of Stanley Stiles must record his indifferent health. Over many years he suffered from migraine, from a stomach ulcer, and from tinnitus; and he

Plate 1 (see facing page). A rough chalk drawing stapled into Stiles's notebook for 23.1.55. The coloured discs are clearly intended to represent the appearance of Maxwell's spot when metameric colour matches are made for a 10-deg field. The faint five-digit number chalked against each disc indicates, as a wavenumber, the variable component in the match. The conditions thus are as follows:

in upper field in lower field

When a perfect match has been achieved for the outer parts of the field, an inhomogeneity- Maxwell's spot-remains in the centre.

was a frequent victim to colds and influenza. During the 1940s he sometimes conducted research 'by remote control' from his sickbed, his assistant, Kenneth Spring, bringing results to him in the evening. Dr Spring recalls

"I remember taking the letter from No. 10, offering the OBE, up to him in bed-where, as usual, he was puffing his pipe."

Perhaps because he published in obscure places, perhaps because he was not working in a university department, perhaps because he was too far ahead of his time, Stiles did not attract in his middle years the recognition that was his due. It is striking that interest in his X-mechanisms reached its peak during the 1970s, a decade after he had retired. In September 1985, shortly before his death, a symposium was held in his honour in Pefiiscola, Spain. The present issue of Perception has evolved from that symposium.

John Mollon Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB. UK

Bibliography F Rinne's Crystals and the Fine Structure of Matter translated by W S Stiles from the German

(London: Methuen, 1924) "Recent measurements of the effect of glare on the brightness difference threshold" in Commis-

sion Internationale de I'Eclairage, Septiime Session: Recueil des Travaux et Compte Rendu des Seances (Teddington: The National Physical Laboratory, 1928) pp 220-238

"On the intensity of the scattered light from an unpolarized beam" Philosophical Magazine 7 204 (1929)

"Glare and visibility in artificially lighted streets" Illuminating Engineer (London) 22 195 - 199, 233-241 (1929)

'Talbot's Law, fatigue and non-linearity in photoelectric cells" Philosophical Magazine 7 812-820 (1929)

"The effect of glare on the brightness difference threshold" Proceedings of the Royal Society of London, Series B 104 322-351 (1929)

The Effect of Glare on the Brightness Difference Threshold Illumination Research Technical Paper No 8 (London: H M Stationery Office, 1929)

T h e scattering theory of the effect of glare on the brightness difference threshold" Proceedings of the Royal Society of London, Series B 105 13 1 - 146 ( 1929)

'Talbot's Law in photoelectric cells" (with T H Harrison), Philosophical Magazine 8 64-65 (1929)

'The nature and effects of glare" Illuminating Engineer (London) 22 304-309 (1929) A brightness difference threshold meter" Illuminating Engineer (London) 23 279-280 (1930) "The international aviation lighting meeting in Berlin" The Aeroplane 38 882- 886 (1930) Thermionic Emission Radio Research Special Report No 11 (London: H M Stationery Office,

1931) Appraisal of Streetlighting Installations (with C Dunbar), Illumination Research Technical Paper

No 13 (London: H M Stationery Office, 1931) T h e evaluation of glare in streetlighting installations" Illuminating Engineer (London) 24

162- 166, 187- l 8 9 (1931) Proceedings of the International Illumination Congress 1931 edited by W S Stiles (London: Interna-

tional Illumination Congress, 1932) "Mass experiments in streetlighting" in Proceedings of the International Illumination Congress 1931

Ed. W S Stiles (London: International Illumination Congress, 1932) pp 576-583 T h e street lighting requirements of different types of street" (with J F Colquhoun) in

Proceedings of the International Illumination Congress 1931 Ed. W S Stiles (London: Interna- tional Illumination Congress, 1932) pp 584- 591

"Equivalent adaptation levels in localised retina1 areas" (with B H Crawford) in Report of a Joint Discussion on Vision by the Physical and Optical Societies (London: The Physical Society, 1932) pp 194-211

"Comment on visual phenomena and quantum theory" in Report of a Joint Discussion on Vision by the Physical and Optical Societies (London: The Physical Society, 1932) pp 326 - 327

Walter Stanley Stiles 1901 - 1985

G Castelfranchi's Recent Advances in Atomic Physics translated by W S Stiles and J W T Walsh from the Italian (London: J and A Churchill, 1932)

"The luminous efficiency of rays entering the eye pupil at different points" (with B H Crawford) Proceedings of the Royal Society of London, Series B 112 428 -450 (1 933)

"The liminal brightness increment as a function of wavelength for different conditions of the foveal and parafoveal retina" (with B H Crawford) Proceedings of the Royal Society of London, Series B 113 496-530 (1933)

The Evaluation of Glare from Motor Car Headlights (with C Dunbar), Illumination Research Technical Paper No 16 (London: H M Stationery Office, 1934)

''Yellow-blue ratio and personal errors in heterochromatic photometry" Philosophical Magazine 17 660-668 (1934)

"The liminal brightness increment for white light for different conditions of the foveal and parafoveal retina" (with B H Crawford) Proceedings of the Royal Society of London, Series B 116 55- 102 (1934)

"Comparison of the revealing powers of white and coloured headlight beams in fog" Illuminating Engineer (London) 28 31 3 - 31 9 (1 935)

"Bewertung von Autoscheinwerfern hinsichtlich der Blendungsfreiheit" Die Lichttechnik 12 17-22 (1935)

''A brightness difference threshold meter for the evaluation of glare from light sources" (with B H Crawford) Journal of Scientific Instruments 12 177 - 185 ( 1935)

"Glare" Reports on Progress in Physics 3 3 1 0 - 3 1 7 ( 1936) "Problems of headlight illumination: dazzle and fog" Engineering 143 50-52 (1937) Visibility of Light Signals with Special Reference to Aviation Lights (with M G Bennett and

H N Green), Aeronautical Research Committee Reports and Memoranda No 1793 (London: H M Stationery Office, 1937) 68 pages

'The luminous efficiency of monochromatic rays entering the eye pupil at different points and a new colour effect" Proceedings of the Royal Society of London, Series B 123 9 0 - 118 (1937)

"Luminous efficiency of rays entering the eye pupil at different points" (with B H Crawford) Nature (London) 139 246 (1937)

"Visibility in fog" The Electrical Review (London) 121 782 - 783 (1 937) T h e effect of a glaring light source on extrafoveal vision" (with B H Crawford) Proceedings of

the RoyalSociety of London, Series B 122 255-280 (1937) The Use of Coloured Light for Motor Car Headlights Illumination Research Technical Paper No 20

(London: H M Stationery Office, 1937) Review of Grimsehls Lehrbuch der Physik revised by R Tomaschek, volume 2, part 2 Proceedings

of the Physical Society, London 50 620 ( 1938) Review of Grimsehls Lehrbuch der Physik revised by R Tomaschek, volume 2, part 1 Proceedings

of the Physical Society, London 50 977 ( 1938) Review of Die Physik des 20 Jahrhunderts by P Jordan Proceedings of the Physical Society, London

50 977 (1938) Review of The Perception of Light by W D Wright Science Progress 34 163 (1939) Review of Grimsehls Lehrbuch der Physik by R Tomaschek, volume 1, part 1 Proceedings of the

Physical Society, London 51 559 ( 1939) T h e directional sensitivity of the retina and the spectral sensitivities of the rods and cones"

Proceedings of the Royal Society of London, Series B 127 64- 105 (1939) "Variation with temperature of the electrical resistance of carbon and graphite between 0' and

900°C (with L J Collier and W G A Taylor) Proceedings of the Physical Society, London 51 147-152 (1939)

"The directional sensitivity of the retina" Science Progress (London) 33 676 -689 (1939) Review of Introductory Quantum Mechanics by V Rojansky Proceedings of the Physical Society,

London 52 277-278 (1940) Review of Test for Night Vision designed by W D Wright Proceedings of the Physical Society,

London 53 492 (1941) Review of Visibility in Meteorology by W E Knowles Middleton Proceedings of the Physical Society,

London 54 72- 73 (1942) "The effectiveness of lighting: its numerical assessment" (with W D Wright, K J W Craik, and

S J MacPherson) Transactions of the Illuminating Engineering Society 8 4 3 - 5 3 (1 943) "A mean scotopic visibility curve" (with T Smith) Proceedings of the Physical Society, London 56

251 -255 (1944) "Current problems of visual research" (abridged from a lecture given before the Physical

Society, 24 May, 1944) Nature (London) 154 290 - 294 (1944)

"Current problems of visual research" Proceedings of the Physical Society, London 56 329 - 356 (1 944)

"Photometer for measuring the scotopic candlepowers of self-luminous ophthalmic test objects" British Journal of Ophthalmology 28 629-637 (1944)

"Colour vision of the fovea centralis" Nature (London) 155 177 (1944) Review of What is Life? by E Schrodinger Proceedings of the Physical Society, London 57 146

(1945) Review of The Measurement of Colour by W D Wright Proceedings of the Physical Society, London

57 368 (1945) 'A modified Helmholtz line element in brightness-colour space" Proceedings of the Physical

Society, London 58 41 - 65 ( 1946) "The basic sensation curves of the three-color theory" Journal of the Optical Society of America

36 491 -492 (1946) "Separation of the 'blue' and 'green' mechanisms of foveal vision by measurements of increment

thresholds" Proceedings of the Royal Society of London, Series B 133 418 - 434 (1 946) "Wartime problems of glare and dazzle" British Medical Bulletin 5 50- 52 (1947) 'Mechanism of colour vision" Nature (London) 160 664 - 666 ( 1947) 'Binocular colour matching: an essay review of W D Wright's Researches on Normal and Defective

Colour Vision" Science Progress (London) 35 342 - 346 ( 1947) 'Colour phenomena in the perception of fine detail" Nature (London) 160 880-881 (1947) Review of Retina1 Structure and Colour Vision by E N Willmer Proceedings of the Physical Society,

London 59 5 l 8 (1 947) Review of Researches on Normal and Defective Colour Vision by W D Wright Proceedings of the

Physical Society, London 59 326 - 327 ( 1947) 'Mr. T. Smith, F.R.S." Nature (London) 162 987 (1 948) "The physical interpretation of the spectral sensitivity curve of the eye" in Transactions of the

Optical Convention of the Worshipful Company of Spectacle Makers (London: Spectacle Makers' Company, 1948) pp 97- 107

'The directional and spectral sensitivities of the retinal rods to adapting fields of different wavelengths" (with F Flamant), Journal of Physiology (London) 107 187 - 202 (1 948)

'Colour terminology" Nature (London) 162 54-55 (1948) "The visibility of targets in a naval searchlight beam" (with W D Chesterman) in Symposium on

Searchlights (London: Illuminating Engineering Society, 1948) pp 75 - 102 'Apparent shape and size of the pupil viewed obliquely" (with K H Spring) British Journal of

Ophthalmology 32 347 - 354 (1948) "Variation of pupil size with change in the angle at which the light stimulus strikes the retina"

(with K H Spring) British Journal of Ophthalmology 32 340 - 346 (1 948) 'The determination of the spectral sensitivities of the retinal mechanisms by sensory methods"

Nederlands Tijdschrift voor Natuurkunde 15 125 - 145 ( 1 949) "Increment thresholds and the mechanisms of colour vision" Documenta Ophthalmologica 3

138- l 6 3 (1949) "Comments on Wald's derivation of the spectral absorption of the macular pigment" Docurnenta

Ophthalmologica 3 135 - 136 ( 1949) "Investigation of the scotopic and trichromatic mechanisms of vision by the two-colour

threshold technique" Revue d'optique 28 215-237 (1949); reprinted in Reunions dlOpticiens tenues a Paris en Octobre 1946 Eds P Fleury, A Marechal, and C Anglade (Paris: Editions de la Revue d'optique, 1950)

Review of Optique Physiologique Tome 2: Lumikre et Couleurs by Y Le Grand Nature (London) 166 1047 (1950)

"Sensibilidad de bastones y conos en la parafovea" (with J Cabello) Anales de la Real Sociedad Espaiiola de Fisica y Quimica, Serie A: Fkica 46 25 1 - 282 ( 1950)

Review of Recent Advances in the Physiology of Vision by H Hartridge Proceedings of the Physical Society, London, Section B 63 828-829 (1950)

Review of Stereoptics by L P Dudley Journal of Scientific Instruments 28 356 (1951) Review of Eyes in Industry by D A Campbell, W J B Riddell, and A Salusbury MacNalty Science

Progress 39 762-763 (1951) Review of Les Theories Photochimiques Classiques et Quantiques de la Vision et ['Inhibition Nerveuse

en Vision Liminaire by E Baumgardt Nature (London) 168 758 ( 195 1 ) 'Spectral reflexion factor of the cat's tapetum" (with R Gunter and H G W Harding) Nature

(London) 168 293 (1951)

Walter Stanley Stiles 1901 - 1985 665

"The eye, brightness and illuminating engineering" Transactions of the Illuminating Engineering Society 17 241-282 (1952)

"Colour vision: a retrospect" Endeavour 11 33-40 (1952) Review of Colour in ~heory and Practice Ed. H D Murray British Journal of Applied Physics 3 396

(1952) 'Visual properties studied by subjective measurements on the colour-adapted eye" British

Medical Bulletin 9 41 - 49 (1 953) "Further studies of visual mechanisms by the two-colour threshold technique" in Colloquio sobre

Problemas Opticas de la Vision volume 1 (Madrid: Union Internationale de Physique Pure et Appliquke, 1953) pp 65 - 103

"Visual factors in lighting" Illuminating Engineering (New York) 49 77- 91 (1954) "Saturation of the rod mechanism of the retina at high levels of stimulation" (with M Aguilar)

Optica Acta 1 59-65 (1954) "Review of Vision through the Atmosphere by W E K Middleton Proceedings of the Physical

Society, London, Section B 67 166 - 167 (1 954) "The basic data of colour-matching: 18th Thomas Young Oration" Yearbook of the Physical

Society, London 44 - 65 (1955) "Colour specification: possible revision of the C.I.E. system" Nature (London) 176 95-97

(1955) "Interim report to the Commission Internationale de l'ficlairage, Zurich, 1955, on the National

Physical Laboratory's investigation of colour-matching" (with an Appendix by W S Stiles and J M Burch) Optica Acta 2 168- l 8 1 (1955)

"Remarks on the line-element" Farbe 4 275 -279 (1955) "Colour vision" Nature (London) 180 1395 - 1397 (1957) "The average colour-matching functions for a large matching field" in National Physical Labora-

tory (UK) Symposium No 8: Visual Problems of Colour volume 1 (London: H M Stationery Office, 1958) pp 209 -247

Review of The Measurement of Colour 2nd edition, by W D Wright Nature (London) 181 1297-1298 (1958)

Review of Light, Colour and Vision by Y Le Grand Proceedings of the Physical Society, London 71 871 -872 (1958)

Review of The Reproduction of Colour by R W Hunt Nature (London) 184 1092 (1959) "Color vision: the approach through increment-threshold sensitivity" Proceedings of the National

Academy of Sciences of the USA 45 100 - 1 14 ( 1959) 'N.P.L. colour-matching investigation: final report (1958)" (with J M Burch), Optica Acta 6

1-26 (1959) "The trichromatic scheme" in Mechanisms of Colour Discrimination Ed. Y Gallifret (London:

Pergarnon Press, 1960) pp l 8 7 - 195 "Lighting and research" Transactions of the Illuminating Engineering Society 26 53 - 65 (1 96 1 ) 'The colour change of monochromatic light with retina1 angle of incidence" (with J M Enoch)

Optica Acta 8 329-358 (1961) "Adaptation, chromatic adaptation, colour transformation" Anales de la Real Sociedad Espahola

de Fisica y Quimica, Serie A: Fisica 57 149 - 175 ( 196 1 ) "Field trials of color-mixture functions" (with G Wyszecki) Journal of the Optical Society of

America 52 58-75 (1962) "Counting metameric object colours" (with G Wyszecki) Journal of the Optical Society of America

52 313-328 (1962) "The directional sensitivity of the retina" Annals of the Royal College of Surgeons of England 30

73-101 (1962) "Dr John W. T. Walsh" Light and Lighting (September) p 293 (1962) Obituary of John William Tudor Walsh Journal of the Institute of Electrical Engineers 8 483

(1962) Review of Sight, Light and Work by H C Weston Science Progress 5 1 129 (1 963) 'N.P.L. colour-matching investigation: addendum on additivity" Optica Acta 10 229 - 232 ( 1963) 'Interactions among chromatic mechanisms as inferred from positive and negative increment

thresholds" (with R M Boynton and M Ikeda) Vision Research 4 87 - 117 (1964) 'Foveal threshold sensitivity on fields of different colors" Science 145 1016 - 1017 (1964) Color Science (with G Wyszecki) (New York: Wiley, 1967) "Mechanism concepts in colour theory" (Newton Lecture) Journal of the Colour Group 11

106-123 (1967)

"Intersections of the spectral reflectance curves of metameric object colours" (with G Wyszecki) Journal of the Optical Society of America 58 32 - 40 ( 1968)

"Interrelations among Stiles' n-mechanisms" (with M Ikeda and T Uetsuki) Journal of the Optical Society of America 60 406 - 41 5 (1 970)

T h e line element in colour theory: a historical review" in Proceedings of the Helmholtz Memorial Symposium on Colour Metrics, Driebergen, Netherlands, September 1971 (Soesterberg, The Netherlands: AIC Holland, c/o Institute for Perception TNO, 1972) pp 1 - 25

"Rod intrusion in large-field colour-matching" (with G Wyszecki) Acta Chromatica (Japan) 2 155-163 (1973)

"Colour-matching data and the spectral absorption curves of visual pigments" (with G Wyszecki) Vision Research 14 195-207 (1974)

'Counting metameric object color stimuli using frequency-limited spectral reflectance functions" (with G Wyszecki and N Ohta) Journal of the Optical Society of America 67 779 -784 (1977)

"Early threshold observations of transient tritanopia" Appendix to "An anomaly in the response of the eye to light of short wavelengths" by J D Mollon and P G Polden Philosophical Transactions of the Royal Society of London, Series B 278 207 -240 (1977)

Mechanisms of Colour Vision: Selected Papers of W.S.Stiles F.R.S. with a New Introductory Essay (London: Academic Press, 1978)

'The two-colour threshold method and IT mechanisms: historical note" in Colour Vision Deficiencies V Ed. G Verriest (Bristol: Hilger, 1980) pp1 11 - 114

"High-level trichromatic color matching and the pigment-bleaching hypothesis" (with G Wyszecki) Vision Research 20 23 - 37 (1980)

Foreword to Vertebrate Photoreceptor Optics Eds J M Enoch and F L Tobey Jr (Berlin: Springer, 1981)

Color Science 2nd edition (with G Wyszecki) (New York: Wiley, 1982) "Reflections on the past and comments on the present" Perception 15 667 -672 ( 1 986)

0 1986 a Pion publication printed in Great Britain