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Past and current research by the Fisheries Research Board of Canada related to olfactory and visual responses in Pacific salmon is reviewed, including comments on some of the sensory and behavioural relations important in migration.An innate ability to perceive highly dilute odours supports the view that olfaction can be instrumental in detecting a distant source, but the problems of following a well directed course indicate likely support from other sensory paths including visual and acoustico–lateralis responses.A threshold visual sensitivity of about 1/300 that of bright moonlight and an ability to orient at night, with view of the sky only, provide evidence that retinal images may be useful as migratory cues as long as turbidity does not interfere.

A psychophysical model that provides separate measures of judgmental standards and sensitivity is utilized to compare an O’s visual sensitivity for vertical and horizontal movement. The analysis indicates no consistent difference in sensitivity; those asymmetries that do exist simply appear to be due to idiosyncratic judgmental standards.

Resume Pour determiner s'il existe une correlation entre la quantite de pigment melanine et la sensibilite visuelle, on a teste un total de 94 personnes de race blanche et 25 negres apres une adaptation a l'obscurite d'une duree de trente minutes avec une lumiere de fixation. Le seuil moyen pour les negres a ete le tiers de celui des blancs dans la fovea. Parmi les blancs on montre que les individus aux yeux noirs possedent un plus bas minimum de lumiere que les individus aux yeux clairs, bien que les differences entre le groupe aux yeux de couleur moyenne et les autres groupes ne soient pas assez suffisantes pour etre statistiquement constantes pour le nombre des cas. En dehors de la fovea les groupes aux yeux plus pigmentes sont toujours superieurs, quoiqu'ils cessent d'etre signifiants comme la region de sensibilite maxima est atteinte. Ces resultats expliquent la faible vision centrale des albinos et leur vision peripherale apparemment normale. La discussion theorique suggere deux hypotheses pour expl...

Spatial discrimination learning and reversal was studied in sham-operated rats and in rats with frontal ablations. The effect of a light which could function as a cue and/or as a reward in the testing situation was examined. In the sham-operated rats it was found that the rewarding property of the light determined its effect on the spatial discrimination. In the frontal rats it was found that both the rewarding and cue properties of the light determined its effect on spatial discrimination. Although frontal rats learned slower and reversed slower than sham rats under conditions in which no light was present or in which light could neither act as a reward nor as a cue, frontal rats were found to reverse faster than sham rats under conditions in which light could act as a cue. It is concluded that an increased sensitivity to visual stimuli in frontal rats can account for conflicting results of previous studies.

Three methods of paraquat analysis have been examined and a suitable procedure for clinical laboratory use is recommended. The method is rapid and can determine down to 0.01 μg paraquation/ml in a 250-ml aliquot of urine. A rapid spot test with visual sensitivity of 1–1.5 μg ion/ml is also described. Some urine levels following oral ingestion of paraquat are reported, but it was not possible to correlate the levels found with severity of poisoning.

"The effect on visual sensitivity of simultaneous stimulation with a tone was measured. No reliable differences were obtained for either the general or the specific color threshold. These results are discussed with reference to the reported observations that visual acuity is increased in the presence of a simultaneously acting auxiliary stimulus. Since the threshold for light is a direct measure of the sensitivity of the retina, the negative results obtained between sound and sight indicate either (1) that the alleged cortical diffusion is obtainable under particular conditions, not covered by these experiments, or (2) that the mechanism of diffusion is of such a nature that sensitivity for light is not primarily affected." (PsycINFO Database Record (c) 2012 APA, all rights reserved)

On changing instantaneously the external light stimulus applied to the eye, the latter does not also change instantaneously its state of adaptation to that corresponding to the new stimulus. No general definition of the state of adaptation of the eye has been given, or, perhaps, can be given. One can, however, imagine quite clearly that, when the eye is viewing some given external distribution of brightness, the concentration of photochemical substances in the various parts of the retina, the nervous messages sent from retina to brain and the consequent reactions in the latter will all be tending towards certain equilibrium values. When the external brightness distribution is changed, these equilibrium values will also change in the direction of a new set of equilibria. Unfortunately, it is difficult to measure any of these things directly and it is necessary to compromise. Amongst quantities more readily measurable the liminal or threshold responses of the eye occupy an important place. These quantities must be closely related to the actual physical state of the visual system and they are of considerable practical significance in themselves. The problem of the change of visual state with time has therefore been approached by measuring the change of visual sensitivity with time. The general experimental problem is to expose the eye to a certain primary or conditioning stimulus for a given period, then suddenly to change to a different stimulus, called for convenience the secondary stimulus, and to make at intervals thereafter a series of threshold measurements, the secondary stimulus remaining steady. This general specification of the problem may be subdivided as follows : 1—Primary and secondary stimuli the same in pattern. ( а ) Primary stimulus greater than secondary. ( b ) Primary stimulus less than secondary. 2—Primary and secondary stimuli different in pattern. This section may also be subdivided according to whether the secondary stimulation corresponds to ( a ) a higher, ( b ) a lower, or ( c ) the same equilibrium value of the visual test on the test area of the retina which is under investigation.

St~mnzary.-10-element binary patterns of open and blackened circles were tachistoscopically exposed such that 0-10 of the elements appeared on the left of a fixation-cross. The specific orientation relative to fixation was unknown to 0 before exposure. 0 was required to reproduce the pattern of blackened circles on a blank template after each exposure. In each of three experiments a different arrangement of the template for recording responses was used. The usual tendency for greater accuracy for elements at the left was overcome when more than half of the elements had appeared to the left of the fixation-point. The form of response recording afEected rhe results, which were accounted for in terms of visual sensitivity, implicit motor factors, and organizational factors in the memory system of 0. When linear visual patterns are tachistoscopically exposed such that they are bisected by a fixation-point, there is generally greater accuracy of reproduction for those stimulus-elements on the left side of fixacion (Harcum, 1957, 1958; Heron, 1957). This result has occurred when the elements are groups of letters (Heron, 1957) and, sometimes, when they are non-alphabetical (Harcum, 1957, 1958). However, when letter-patterns are exposed totally either to the right or left of the fixation-point, the greater accuracy of reproduction occurs on the right of fixation (Harcum & Jones, 1962; Heron, 1957; Mishkin & Forgays, 1952; Terrace, 1959). With form-stimuli or single letters exposed entirely to the right or left of fixation, reproduction accuracy usually is about equal for target locations both to the left and to the right (Bryden, 1960; Camp, 1960; Heron, 1957; Terrace, 1959). The differences which are sometimes obtained between the alphabetical and non-aphabetical materials are probably due to an inherent directionalicy or polarity associated with letrers of the alphabet (Bryden, 1960), or more simply, it is difficult to read the letters backwards. Three basic factors necessary to explain the above general findings can be associated with the three components of the classical S-0-R sequence, respectively, visual sensitivity or stimulus attensity, memory, and the oculomotor response. These factors are obviously mun~ally interrelated; the distinctions among them are arbitrary for the sake of exposition.

32 children (10 normal readers, 10 non-resistant backward readers, and 12 resistant backward readers) were examined for visual and kinaesthetic sensitivity, as measured by a difference-threshold procedure. Birch's hypothesis that the failure of the visual system to be dominant in sensory systems may lead to reading difficulties was tested. To verify this hypothesis the rank-differences, S's visual minus his kinaesthetic threshold rank, should be larger in backward than in normal readers. Results support the hypothesis In addition, it appeared that the dyslectics differ from normal readers not so much by greater kinaesthetic as by lower visual sensitivity. The existence of a smaller visual dominance in dyslectics may be responsible for kinaesthetic interference in the visual information process in reading.

Binocular visual excitability changes were obtained from two trained observers by presenting a "conditioning" flash of light to one eye and a brief "test" flash to a homologous retinal position in the other. Interval between flashes ranged from –200 msec. (test flash preceding conditioning) to +600 msec. (test following onset of conditioning flash). Results showed that threshold rose when test preceded conditioning flash, reaching a maximum increment of 0.5 log ml at –25 msec. separation. When test was superimposed upon conditioning flash in time, threshold dropped sharply to reach a relatively constant but elevated value for the duration of the conditioning flash. No excitability changes were obtained, however, if the test and conditioning flashes were displaced so as to stimulate adjacent rather than "corresponding" retinal points. These findings indicate that central (retrochiasmal) factors can influence visual sensitivity, the magnitude of this influence varying with the spatial and the temporal relations between successive light flashes. This conclusion is compatible with recent electrophysiological data on excitability changes in the cerebral visual system.

Binocular fusion may be due to interocular inhibitory suppression, an hypothesis difficult to evaluate by phenomenal inspection. A test probe method (reaction time to a light pulse) was used to measure visual sensitivity during binocular rivalry and fusion. The absence of inhibitory effects during fusion fails to support the suppression theory of fusion.

An investigation to determine the possibility of a relationship between visual acuity and phases of the menstrual cycle was undertaken in 4 women (ages 17 to 19) at various stages of their cycles. Visual se nsitivity as measured by the ability to detect a test light was found to be lowest during menstruation progressively increasing until midcycl e (at the approximate time of ovulation) when it leveled off. Sensitivi ty then remained high for the remainder of the premenstrual phase and declined again at menses. A fairly stable level of visual sensitivity was observed in a control group of women taking nonsequential oral contraceptives and in men tested at the same time intervals. These results suggest that visual functions are affected by cyclic hormonal changes. These and other sensory changes increase the probability that coitus would occur at the time of ovulation thus increasing the probability of conception.

To investigate the precise mechanism of control of binocular rivalry, Ss were instructed to attend actively to whichever pattern was momentarily in the nonsuppression phase. Test stimuli were presented tachistoscopically for recognition in either phase of rivalry. Because the differential recognition between nonsuppressed and suppressed phases was no greater for an active condition than for a passive viewing condition, it was concluded that control is not mediated by varying the amplitude of the suppression effect. This result was consistent with control that is exercised by selecting the eye to receive a constant amplitude suppression. In addition, it was found that visual sensitivity of rivalry nonsuppression and nonrivalry were the same for the ocular dominant eye but different for the nondominant eye.

Behavioral measurements of visual sensitivity and color vision were made on a common species of North American ground squirrel ( Citellus beecheyi ) whose retina contains only cone receptors. Several features of visual capacity were assessed: spectral sensitivity (including measures that could reveal the occurrence of a Purkinje shift), tests for the presence of a spectral neutral point, and tests for points of chromaticity confusion. The results indicate that: (a) the spectral sensitivity function peaks at 520 nm in this species and varies somewhat in shape under different conditions of adaptation; (b) no Purkinje shift can be seen; (c) each animal has a distinct neutral point in the region of 505 nm (d) the copunctal point for the California ground squirrel ( C. beecheyi ) is similar to the copunctal point reported for human protanopes. The results were found to agree closely with results obtained previously from two other species of ground squirrels.

While there is a distinction between that intensity of illumination which permits social wasps to forage, and that to which a sessile worker can respond, nevertheless illumination is the most critical of the environmental factors which control the activity of wasps. Low temperatures, high winds, and heavy rain all reduce activity but unless exceptionally severe do not wholly stop it. At dawn, when the critical level of illumination is attained, workers leave the nest, but at dusk they will not leave should the same critical level be due in the course of the foraging flight, after which they could not return. The three species of wasp,Vespula vulgaris, V. rufa, andV. germanica have a common threshold of illumination, although the hornet,Vespa crabro can forage in moonlight at an altogether lower illumination. Honey-bees normally need a still higher illumination than do wasps. In all these species, the thresholds of illumination are related to the length of the compound eyes, so that species with large eyes need less light by which to forage. Moreover, there is a slight difference between the threshold at dawn when workers leave the nest, and that at dusk, when they must needs have sufficient light by which to return. This difference is almost constant for each species, when, as is customary, one measures it on a logarithmic scale. Lastly, the estimates, which these experiments provide, of the threshold illuminations depend stochastically on the number of workers foraging. A correction for this bias is given.

Wright W. VII. - The visual sensitivity of normal and aphakic observers in the ultra-violet. In: L'année psychologique. 1949 vol. 50. pp. 169-177.

Ten experiments are reported. In each the effect of a heteromodal stimulus on visual sensitivity is investigated. With one exception all the stimuli produced a small increase in visual sensitivity. A number of possible explanations of intersensory facilitation are considered.

1. Visual sensitivity to movement in depth was measured as a function of the relative distances through which the left and right retinal images moved. This relative distance (left:right ratio) provides a sensitive cue to the direction along which a target moves in three-dimensional space. 2. Gazing at a target which moved along a fixed direction in space produced a gross reduction of visual sensitivity to movements in depth along that direction. For other directions of movement, visual sensitivity was not affected. 3. Sensitivity to depth movement rapidly rose almost to the preadaptation level within the first 20–60 sec after removing the adapting target, but recovery was not complete until 100–300 min had elapsed. 4. Any adapting target whose left:right ratio fell within a definite range gave similar reductions of visual sensitivity to movements in depth. There were five such ranges. 5. The effects of adapting to movement in depth suggest that eight mechanisms underlie depth perception. These mechanisms are ‘tuned’ to the direction of movement in three-dimensional space. Four mechanisms are wholly concerned with movements along directions very close to the line which cuts midway between the eyes, and do not respond to movements whose direction departs by more than 1·5° from the preferred direction. 6. Neural mechanisms ‘tuned’ to different left:right ratios could provide a physiological basis for sensing the direction in which an object moves in three-dimensional space.

ENIGMA is a term not customarily associated with realist painters. Nevertheless, Edouard Manet's Mademoiselle Victorine in the Costume of an Espada ( 862), in The Metropolitan Museum of Art (Figure I),1 must be regarded as an enigmatic work. Before a Goyesque backdrop of a bullfighting scene stands the full-length figure ofVictorine Meurend, Manet's favorite model in 1862 and for several years thereafter, dressed in Spanish male costume and posed as though for a photographer. The brilliantly and realistically rendered figure, obviously painted before the model, testifies to Manet's visual sensitivity and manual dexterity, but in its relation to the background scene violates the laws of linear perspective in a manner so obvious as to seem deliberate. Indeed, the artificiality of the whole arrangement, noted by critics in 1863 and frequently since, can best be interpreted as the result of a carefully constructed interplay of colors and values, responding more to abstract pictorial exigencies than to the visual experience of spatial relationships. Alternating bands of dark and light in the background serve to silhouette op

Measurements of ΔI as a function of retinal area illuminated have been obtained at various levels of standard intensity I1, using "white" light and light of three modal wave-lengths (λ465, 525, 680), for monocular stimulation and for simultaneous excitation of the two eyes ("binocular"), using several methods of varying (rectangular) area and retinal location, with control of exposure time. For data homogeneous with respect to method of presentation, log ΔIm = -Z log A + C, where ΔI = Ĩ2 – I1, A is area illuminated, and C is a terminal constant (= log ΔIm for A = 1 unit) depending on the units in which ΔI and A are expressed, and upon I1. The equation is readily deduced on dimensional grounds, without reference to specific theories of the nature of ΔI or of retinal area in terms of its excitable units. Z is independent of the units of I and A. Experimentally it is found to be the same for monocular and binocular excitations, as is to be expected. Also as is expected it is not independent of λ, and it is markedly influenced by the scheme according to which A is varied; it depends directly upon the rate at which potentially excitable elements are added when A is made to increase. For simultaneous excitation of the two eyes (when of very nearly equivalent excitability), ΔĪB is less than for stimulation of either eye alone, at all levels of I1, A, λ. The mean ratio (ΔĪL + ΔĪR)/2 to ΔIB was 1.38. For white light, doubling A on one retina reduces ΔIm in the ratio 1.21, or a little less than for binocular presentation under the same conditions. These facts are consistent with the view that the properties of ΔI are quantitatively determined by events central to the retina. The measure σ1ΔI of organic variation in discrimination of intensities and ΔIm are found to be in simple proportion, independent of I1, A, λ (and exposure time). Variability (σ1ΔI) is not a function of the mode of presentation, save that it may be slightly higher when both retinas are excited, and its magnitude (for a given level of ΔIm) is independent of the law according to which the adjustable intensity I2 is instrumentally controlled.

THE human visual system responds with transient losses of sensitivity when background light levels are suddenly increased or decreased. Crawford1 measured the early threshold changes in humans by means of a small circular test flash presented before, during and after presentation of a larger diameter adapting light. He found that threshold increased just before the onset of the adapting light, reached a peak shortly after onset, and then decreased during the subsequent 0.5 s. Immediately before the offset of the adapting light, threshold increased slightly, peaked at offset and then returned to its original level. Other investigators have reported essentially the same results under various conditions2–4. The increase in visual sensitivity during the first few seconds of light adaptation and the peaked loss of sensitivity at the offset of the adapting light are in the wrong direction as predicted by bleaching of the photopigments. Consequently, Baker5 suggested that neural factors account for the early change in visual adaptation. Unfortunately, the question of mechanisms involved to account for these rapid changes in visual sensitivity cannot be answered from psychophysical experiments since the response range cannot be assessed during these periods.

Previous studies of saccadic suppression do not rule out the possibility that the phenomenon may be affected by, or produced by, shifts of the Os’ criteria for reporting a flash. The present study, using a presumably criterion-free measure (d’), demonstrates a decrease in visual sensitivity beginning as much as 150–200 msec prior to a voluntary saccade. It is suggested that criterion-free measures of visual sensitivity be used in future studies of the saccadic suppression.

THE dorsal ocelli of adult insects are present in some representatives of almost all orders except Collembola and Ephemeroptera1. Despite their wide occurrence among orders of insects, most hypotheses of their function have usually been ad hoc (for summaries of theories, see refs. 2–4). The physiological nature of the organs, their diversity throughout thousands of species, and their complex role in the integration of behaviour have not yet been thoroughly explored. Knowledge about these organs has begun to accumulate, and recent behavioural works on bees5,6 and on wasps7 give rise to the possibility that the ocelli may be associated more closely with visual perception than was previously thought. This communication is a preliminary report of the possibility that the ocelli act as visual sensitivity adjusters.

The study examined the effect of a continuous 1,000-Hz 80-dB accessory tone upon the detectability of a visual stimulus presented to the peripheral retina. All Ss received the primary visual stimulus both with and without an accessory auditory stimulus. Detection of the visual stimulus was measured by means of a forced-choice indicator. The presence of the accessory tone significantly decreased the percentage of light detections. An unexpected finding was that incorrect responses were unequally distributed among the four observation intervals. It was concluded that continuous intense accessory auditory stimulation inhibits visual sensitivity.

THE isolated retina is a useful preparation for studying many aspects of visual sensitivity. Photochemical changes following exposure to light may be studied directly, and concomitant electrical events may be monitored with gross and micro-electrodes. The photopigment is also not appreciably regenerated during an experiment, and loss of sensitivity following light exposure shows a clear relationship to visual pigment concentration.

The present research studied the effects for two-choice, discrete-trial, pattern-discrimination learning of changes in the stimulus-information content of both the positive and negative stimulus cues. The major findings suggest that, with experienced primates, there exists a relation between equal increments in positive and negative stimulus information and discrimination learning that is strikingly similar to the classical psychophysical relationship between stimulus intensity and JNDs.

The biological importance of the daily light-dark-cycle for man has received insufficient investigation, especially since the importance of natural and artificial light as a Zeitgeber of the circadian system has been proved in animal experiments. The periodic variation in the responsiveness of the circadian system to the Zeitgeber stimulus is an important endogenous precondition for the efficiency of the Zeitgeber.

When a target's retinal disparity changes with a pulsed waveform, the target appears to execute a pulsed movement in depth. Visual sensitivity to such disparity changes was plotted as a function of pulse duration. These curves resembled low-pass filter characteristics. For a given direction of movement in depth, different sensitivity curves were obtained for targets located in front of and behind the plane of binocular fixation. However, depth sensitivities were similar for pulses directed from either locationtowards the fixation plane or directed from either locationaway from the plane. This suggests that movements in depth directed towards and away from the fixation plane are handled by different neural mechanisms in man in accord with single-neuron evidence in cat and monkey.

The threshold for a small spot of light rises as it approaches the edge of an illuminated area and gradually falls in the dark. The threshold rise on the illuminated side of the edge was found to be dependent on the intensity of the illuminated field, absent at low in tensity. Short duration flashes of both edge and test spot abolished the threshold elevation on the illuminated side of the edge regardless of field intensity. While the threshold rise may be associated with lateral inhibitory effects, the fall in the dark was shown to be due to stray light in the eye.

Albino rats were exposed to 440 foot candles of either continuous light (LL) or cyclic light (LD) for 12 weeks. Then the 75% visual difference threshold was measured by means of an adaptive behavioral psychophysical technique. The difference threshold of the LL rats was 2.2 log units higher than that of the LD rats, indicating that visual sensitivity was greatly reduced following exposure to constant light. In addition, an electrophysiological measure, the early receptor potential, was employed to assess the functional capability of retinal receptor cells in LL and LD rats to respond to light. The mean response of the LL retinas was 10 μV and that of LD retinas 165 μV. These data indicate that when the albino rat is exposed to constant light there is a significant decrease in visual sensitivity. The observed loss of sensitivity is probably due to a reduction in the number of rod outer segments and in the level of rhodopsin.

Isolated perfused retinas of albino rats were exposed to brief saturating flashes of white light which bleached about 50 percent of the rhodopsin present. Transient photoproducts of the reaction could be detected for about 30 minutes. The b-wave threshold increased by some 3 logarithmic units immediately after the flash and remained stable at this level thereafter. This suggests that the longer-lived intermediate products of rhodopsin photolysis do not influence scotopic visual sensitivity.

Test-stimulus thresholds were determined as a function of the interval separating the masking- and test-stimuli onsets as a darkened area in the visual field was exposed binocularly once each 750±5 ms for a duration of 21, 42, or 188 ms. Increased test-stimulus thresholds were observed following the onset of the masking stimulus and were directly related to the duration of the dark interval. These results demonstrated that when the eyes are briefly exposed to a dark interval, transient fluctuations in visual sensitivity occur. Such sensitivity changes, which are likely of neural origin, affect the magnitude of masking effects.

THE physiological function of the tapetum in the eyes of animals of nocturnal habit is uncertain. However, it may fairly be assumed that by reflecting light incident on the retina back through the layer of end-organs, the tapetum reduces in some measure the absolute threshold for vision1. Since the tapetum is coloured, spectral sensitivities determined from absolute thresholds will also be modified. Murr2, working on the light sense of the domestic cat, attributed differences in the wave-length of maximum visual sensitivity to differences in tapetum colour. In particular, he suggested that there occur changes of this kind during the life of the animal.

Conditioning stimuli of differing luminances, which appear equally bright because of the effects of previous light adaptation, may produce essentially equivalent on-responses, as evaluated by the temporal changes in the threshold of a superimposed test flash. The magnitude of these responses is directly related not to the actual luminance of the conditioning stimulus in each case, but to its brightness. Over a fairly wide range of conditions of light adaptation and brightness, constant brightness is accompanied by constant changes in log visual sensitivity, as assessed both by an increment threshold and the conditioning-stimulus-test-flash-threshold techniques.Only at intermediate sensitivity levels is there any evidence for a simple “filter factor” model for the light-adaptation mechanism. The visual response at the extremes of the sensitivity range appears to approach physiological limits which render a simple model of the effects of light adaptation untenable.

In this paper, I plan to talk about the latest in a series of experiments on visual masking which were done over the past several years at Rochester. Peter Schiller’s very lucid presentation (P. H. Schiller, this volume) provides an excellent background for this, and gives one something to think about in the electrophysiological domain, which might be helpful in trying to explain our results. The present experiment was actually carried out by Robert Kintz, a graduate student at Rochester.

The spectral sensitivity between 448 nm and 655 nm of a dark-adapted bush baby, Galago crassicaudatus agisymbanus, Coquerel, was determined by an automated behavioural method. The animal was trained to work continuously, unattended, in a modified Y-maze with a food reward, going to a stimulus light whose intensity was subject to negative feed-back from the animal's success. Digital counters recorded correct and wrong runs at each intensity level, and a threshold was derived from the frequency-of-seeing curve. The mean absolute behavioural threshold of the bush baby was 0.13 log units less sensitive than the corresponding human threshold, and the most sensitive results about 0.5 log units more sensitive than the human. The behavioural spectral sensitivity results support the conclusion (Dartnall et al., 1965) drawn from the ERG spectral sensitivity, that fluorescence as well as tapetal reflectance contributes to the visual sensitivity of the bush baby.

This report describes two experiments with electroluminescent aircraft instrument lighting. In the first experiment, white electroluminescent, green electroluminescent, and red incandescent lighting were compared for their effects on dark-adapted, scotopic absolute and acuity thresholds, using a simulated T-38 instrument panel for light exposure. In the second experiment, white, green, and yellow electroluminescent and red incandescent light were compared in terms of legibility of a transilluminated letter-acuity chart. Exposure to red incandescent lighting at 0.05 ft.-l. produced the lowest absolute and acuity thresholds, with white and green electroluminescent producing higher thresholds in that order. Although threshold differences between lighting colors were statistically significant, the absolute differences in visual sensitivity were small for practical purposes. Luminances required for equal legibility of transilluminated letters of various sizes were about the same for red incandescent, and white, green, and yellow electroluminescent lamps. Electroluminescent lighting of aircraft instruments is discussed.