A new Mooney test.

Since its introduction in 1957, the Mooney test has continued to see active use in studies of visual perception, in studies using brain imaging, and in clinical research. Mooney's original version is of limited length, however, and was designed to be administered by time-consuming personal interview. We have developed a new, extended version of the Mooney test that is suitable for online testing and for use in a test-retest paradigm. The Mooney-Verhallen Test (MVT) comprises 144 trials, takes on average less than 10 min to complete, and has a Spearman-Brown-corrected test-retest reliability of ρ = .89. We outline our methods for developing the stimuli and for selecting the final stimulus set, and we present the results from two rounds of testing on two independent samples of 374 participants and 505 participants, respectively. The test is freely available for scientific use.RJV is grateful for funding received from the Prins Bernhard Cultuurfonds, the Hendrik Muller Fonds, the Grindley Fund, and the Cambridge Philosophical Society.This is the author accepted manuscript. The final version is available from Springer via http://dx.doi.org/10.3758/s13428-015-0666-

Cerebral iconics: How are visual stimuli represented centrally in the human brain?

In the case of some sensory attributes (e.g., luminance), differential thresholds increase with the spatial separation between the stimuli to be compared, but in other cases (e.g., spatial frequency, hue) thresholds vary little whether the stimuli are close together or separated by 10 degrees of arc. To this latter class of sensory attributes, we here add two dimensions: Speed of motion and chromatic purity. Stimuli were presented too briefly for an eye movement and could fall at any positions on an imaginary circle centered on the fixation point. What neural mechanisms underlie discrimination in such tasks? We doubt discrimination depends on a large array of dedicated "comparator neurons," one for each possible pair of positions in the visual field and for each sensory attribute. Instead we suggest that information about local sensory properties is carried to the cortical site of comparison by neural connections that resemble the man-made Internet insofar as the same physical substrate from moment to moment carries different information in a symbolic code

Is discrimination enhanced at a category boundary? The case of unique red.

Is chromatic discrimination enhanced at the boundary between different hues? In previous studies, we gave a positive answer for the case of the locus of unique blues and yellows, the boundary that divides color space into reddish and greenish hues. But we did not find enhancement at the locus of unique green, the boundary between yellowish and bluish hues. In the present study, we examined discrimination near the locus of unique red. In interleaved experimental runs, we obtained (1) discrimination thresholds using a four-alternative spatial forced choice and (2) phenomenological judgments of the locus of unique red. When measurements were made along lines parallel to the locus of unique blues and yellows in a MacLeod-Boynton diagram, the locus of minimal thresholds coincided approximately with the locus of unique red; however, this was not the case when measurements were made along lines orthogonal to the locus of unique blues and yellows. To account for these and earlier results, we suppose that the neural channel that determines the discrimination threshold will sometimes coincide with the channel that determines the perceptual hue equilibrium and sometimes will not. If a given point in chromaticity space is a unique hue, then it is expected to remain a unique hue independently of the direction in which measurements are made; however, discrimination thresholds almost certainly will depend on different underlying channels when measurements are made in different directions through the same point in chromaticity space.This is the author accepted manuscript. The final version is available from the Optical Society of America via http://dx.doi.org/10.1364/JOSAA.33.00A26

Syringe labels seen through the eyes of the colour-deficient clinician

In the hospital environment, a common use of colour is to distinguish between variants of a piece of equipment, for example blood tubes or sizes of cannula. There is little guidance on which colours should be used in constructing a safe and helpful colour code, and the choice is generally left to manufacturers. A rare exception to this is the labelling of syringes in critical care areas, for which clear and well thought out guidance is provided in the UK.1This guidance is backed by the Royal College of Anaesthetists, the Association of Anaesthetists of Great Britain and Ireland, the Royal College of Emergency Medicine, the Intensive Care Society, and the Faculty of Intensive Care Medicine. Similar guidelines are issued in the USA,2 and there is also an ISO (International Organization for Standardization) standard.3 For the individual with normal colour vision, there is little scope for confusion with such labels, as they use a mixture of colour, hatching, and reversal of font and background colour. There is evidence that syringe labelling systems can enhance the safe use of medication.4National Institute for Health Research (NIHR) Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology

Superior discrimination for hue than for saturation and an explanation in terms of correlated neural noise.

The precision of human colour discrimination depends on the region of colour space in which measurements are made and on the direction in which the compared colours-the discriminanda-differ. Working in a MacLeod-Boynton chromaticity diagram scaled so that thresholds at the white point were equal for the two axes, we made measurements at reference points lying on lines that passed at 45° or -45° through the white point. At a given reference chromaticity, we measured thresholds either for saturation (i.e. for discriminanda lying radially along the line passing through the white point) or for hue (i.e. for discriminanda lying on a tangent of a circle passing through the reference point and centred on the white point). The discriminanda always straddled the reference point in chromaticity. The attraction of this arrangement is that the two thresholds can be expressed in common units. All that differs between saturation and hue measurements is the phase with which the short-wave signal is combined with the long-/middle-wave signal. Except for chromaticities very close to the white point, saturation thresholds were systematically higher than hue thresholds. We offer a possible explanation in terms of correlated neural noise.This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by Royal Society Publishing

'The last channel': vision at the temporal margin of the field.

The human visual field, on the temporal side, extends to at least 90° from the line of sight. Using a two-alternative forced-choice procedure in which observers are asked to report the direction of motion of a Gabor patch, and taking precautions to exclude unconscious eye movements in the direction of the stimulus, we show that the limiting eccentricity of image-forming vision can be established with precision. There are large, but reliable, individual differences in the limiting eccentricity. The limiting eccentricity exhibits a dependence on log contrast; but it is not reduced when the modulation visible to the rods is attenuated, a result compatible with the histological evidence that the outermost part of the retina exhibits a high density of cones. Our working hypothesis is that only one type of neural channel is present in the far periphery of the retina, a channel that responds to temporally modulated stimuli of low spatial frequency and that is directionally selective.Evelyn Trus

Speed and the coherence of superimposed chromatic gratings.

On the basis of measurements of the perceived coherence of superimposed drifting gratings, Krauskopf and Farell (1990) proposed that motion is analysed independently in different chromatic channels. They found that two gratings appeared to slip if each modulated one of the two 'cardinal' color mechanisms S/(L+M) and L/(L+M). If the gratings were defined along intermediate color directions, observers reported a plaid, moving coherently. We hypothesised that slippage might occur in chromatic gratings if the motion signal from the S/(L+M) channel is weak and equivalent to a lower speed. We asked observers to judge coherence in two conditions. In one, S/(L+M) and L/(L+M) gratings were physically the same speed. In the other, the two gratings had perceptually matched speeds. We found that the relative incoherence of cardinal gratings is the same whether gratings are physically or perceptually matched in speed. Thus our hypothesis was firmly contradicted. In a control condition, observers were asked to judge the coherence of stationary gratings. Interestingly, the difference in judged coherence between cardinal and intermediate gratings remained as strong as it was when the gratings moved. Our results suggest a possible alternative interpretation of Krauskopf and Farell's result: the processes of object segregation may precede the analysis of the motion of chromatic gratings, and the same grouping signals may prompt object segregation in the stationary and moving cases.J.B. was supported by a Research Fellowship from Gonville and Caius College, and L.S. by the Amgen Scholars Programme.This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by Elsevier

A population study of binocular function.

As part of a genome-wide association study (GWAS) of perceptual traits in healthy adults, we measured stereo acuity, the duration of alternative percepts in binocular rivalry and the extent of dichoptic masking in 1060 participants. We present the distributions of the measures, the correlations between measures, and their relationships to other psychophysical traits. We report sex differences, and correlations with age, interpupillary distance, eye dominance, phorias, visual acuity and personality. The GWAS, using data from 988 participants, yielded one genetic association that passed a permutation test for significance: The variant rs1022907 in the gene VTI1A was associated with self-reported ability to see autostereograms. We list a number of other suggestive genetic associations (p<10(-5)).This work was supported by the Gatsby Charitable Foundation (GAT2903). J.B. was supported by a fellowship from Gonville and Caius College.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.visres.2015.02.01

An online version of the Mooney Face Test: phenotypic and genetic associations.

The Mooney Face Test is a widely used test of face perception, but was originally designed to be administered by personal interview. We have developed a three-alternative forced-choice version for online testing. We tested 397 healthy adults between the ages of 18 and 42 (M=24 years). There was a wide range of performance (64-100% correct; M=89.6%). We observed a significant sex difference favoring males (.31 standard deviation; p =.004). In addition, independently of sex, higher 2D:4D digit ratios were significantly associated with higher scores (ρ=.14, p=.006). A genome-wide association study (GWAS) for a subset of 370 participants identified an association between Mooney performance and a polymorphism in the RAPGEF5 gene (rs1522280; p=9.68×10(-8)). This association survives a permutation test (p=.031).This is the author's accepted manuscript. The final version of this paper is published by Elsevier in Neuropsychologia here: http://www.sciencedirect.com/science/article/pii/S0028393214002747

The Oxytocin Receptor Gene ( OXTR) and Face Recognition.

A recent study has linked individual differences in face recognition to rs237887, a single-nucleotide polymorphism (SNP) of the oxytocin receptor gene ( OXTR; Skuse et al., 2014). In that study, participants were assessed using the Warrington Recognition Memory Test for Faces, but performance on Warrington's test has been shown not to rely purely on face recognition processes. We administered the widely used Cambridge Face Memory Test-a purer test of face recognition-to 370 participants. Performance was not significantly associated with rs237887, with 16 other SNPs of OXTR that we genotyped, or with a further 75 imputed SNPs. We also administered three other tests of face processing (the Mooney Face Test, the Glasgow Face Matching Test, and the Composite Face Test), but performance was never significantly associated with rs237887 or with any of the other genotyped or imputed SNPs, after corrections for multiple testing. In addition, we found no associations between OXTR and Autism-Spectrum Quotient scores.This work was supported by Gatsby Charitable Foundation Grant GAT2903