Skip to main content
    • Aa
    • Aa

The gap effect is exaggerated in parafovea


In central vision, the discrimination of colors lying on a tritan line is improved if a small gap is introduced between the two stimulus fields. Boynton et al. (1977) called this a “positive gap effect.” They found that the effect was weak or absent for discriminations based on the ratio of the signals of long-wave and middle-wave cones; and even for tritan stimuli, the gap effect was weakened when forced choice or brief durations were used. We here describe measurements of the gap effect in the parafovea. The stimuli were 1 deg of visual angle in width and were centered on an imaginary circle of radius 5 deg. They were brief (100 ms), and thresholds were measured with a spatial two-alternative forced choice. Under these conditions we find a clear gap effect, which is of similar magnitude for both the cardinal chromatic axes. It may be a chromatic analog of the crowding effect observed for parafoveal perception of form.

Corresponding author
Address correspondence and reprint requests to: Marina Danilova, Pavlov Institute of Physiology, Nab. Makarova 6, St. Petersburg 199034, Russia. E-mail:
Linked references
Hide All

This list contains references from the content that can be linked to their source. For a full set of references and notes please see the PDF or HTML where available.

Bouma, H. (1970). Interaction effects in parafoveal letter recognition. Nature226, 177178.

Boynton, R.M., Hayhoe, M.M., & MacLeod, D.I.A. (1977). The gap effect: Chromatic and achromatic visual discrimination as affected by field separation. Optica Acta24, 159177.

Brindley, G.S. (1954). The summation areas of human colour-receptive mechanisms at increment threshold. Journal of Physiology124, 400408.

Cottaris, N.P. & De Valois, R.L. (1998). Temporal dynamics of chromatic tuning in macaque primary visual cortex. Nature395, 896900.

Dacey, D.M. & Lee, B.B. (1994). The “blue-on” opponent pathway in primate retina originates from a distinct bistratified ganglion cell type. Nature367, 731735.

Danilova, M.V. & Mollon, J.D. (2003). Comparison at a distance. Perception32, 395414.

Danilova, M.V. & Mollon, J.D. (2006). The comparison of spatially separated colours. Vision Research46, 823836.

Eskew, R.T. (1989). The gap effect revisited: Slow changes in chromatic sensitivity as affected by luminance and chromatic borders. Vision Research29, 717729.

Eskew, R.T. & Boynton, R.M. (1987). Effects of field area and configuration on chromatic and border discrimination. Vision Research27, 18351844.

Eskew, R.T., Stromeyer, C.F., Picotte, C.J., & Kronauer, R.E. (1991). Detection uncertainty and the facilitation of chromatic detection by luminance contours. Journal of the Optical Society of America A8, 394403.

Hess, R.F. & Jacobs, R.J. (1979). A preliminary report of acuity and contour interactions across the amblyope's visual field. Vision Research19, 14031408.

Hilz, R.L., Huppmann, G., & Cavonius, C.R. (1974). Influence of luminance contrast on hue discrimination. Journal of the Optical Society of America64, 763766.

Krauskopf, J., Williams, D.R., & Heeley, D.W. (1982). Cardinal directions of color space. Vision Research22, 11231131.

Levi, D.M., Hariharan, S., & Klein, S.A. (2002). Suppressive and facilitatory spatial interactions in peripheral vision: Peripheral crowding is neither size invariant nor simple contrast masking. Journal of Vision2, 167177.

MacLeod, D.I.A. & Boynton, R.M. (1979). Chromaticity diagram showing cone excitation by stimuli of equal luminance. Journal of the Optical Society of America69, 11831186.

McKeefry, D.J., Parry, N.R.A., & Murray, I.J. (2003). Simple reaction times in color space: The influence of chromaticity, contrast, and cone opponency. Investigative Ophthalmology and Visual Science44, 22672276.

Montag, E.D. (1997). Influence of boundary information on the perception of color. Journal of the Optical Society of America A14, 9971006.

Parkes, L., Lund, J., Angelucci, A., Solomon, J.A., & Morgan, M. (2001). Compulsory averaging of crowded orientation signals in human vision. Nature Neuroscience4, 739744.

Pelli, D.G., Palomares, M., & Majaj, N.J. (2004). Crowding is unlike ordinary masking: Distinguishing feature integration from detection. Journal of Vision4, 11361169.

Regan, B.C., Reffin, J.P., & Mollon, J.D. (1994). Luminance noise and the rapid determination of discrimination ellipses in colour deficiency. Vision Research34, 12791299.

Rentschler, I. & Fiorentini, A. (1974). Meridional anisotropy of psychophysical spatial interactions. Vision Research14, 14671473.

Sankeralli, M.J. & Mullen, K.T. (2001). Bipolar or rectified chromatic detection mechanisms. Visual Neuroscience18, 127135.

Sharpe, L.T. & Wyszecki, G. (1976). Proximity factor in color-difference evaluations. Journal of the Optical Society of America66, 4049.

Smith, V.C. & Pokorny, J. (1975). Spectral sensitivity of the foveal cone photopigments between 400 and 500 nm. Vision Research15, 161171.

Smithson, H.E. & Mollon, J.D. (2004). Is the S-opponent chromatic sub-system sluggish?Vision Research44, 29192929.

Stiles, W.S. (1949). Increment thresholds and the mechanisms of colour vision. Documenta Ophthalmologica3, 138163.

Stockman, A. & Sharpe, L.T. (2000). The spectral sensitivities of the middle- and long-wavelength-sensitive cones derived from measurements in observers of known genotype. Vision Research40, 17111737.

Tansley, B.W. & Boynton, R.M. (1976). A line, not a space, represents visual distinctness of borders formed by different colors. Science191, 954957.

Traub, A.C. & Balinkin, I. (1961). Proximity factor in the Judd color difference formula. Journal of the Optical Society of America51, 755760.

Vassilev, A., Mihaylova, M.S., Racheva, K., Zlatkova, M., & Anderson, R. (2003). Spatial summation of S-cone ON and OFF signals: Effects of retinal eccentricity. Vision Research43, 28752884.

West, M., Spillmann, L., Cavanagh, P., Mollon, J., & Hamlin, S. (1996). Susanne Liebmann in the critical zone. Perception25, 14511495.

Wetherill, G.B. & Levitt, H. (1965). Sequential estimation of points on a psychometric function. British Journal of Mathematical and Statistical Psychology18, 110.

Wolford, G. & Chambers, L. (1984). Contour interaction as a function of retinal eccentricity. Perception and Psychophysics36, 457460.

Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

Visual Neuroscience
  • ISSN: 0952-5238
  • EISSN: 1469-8714
  • URL: /core/journals/visual-neuroscience
Please enter your name
Please enter a valid email address
Who would you like to send this to? *



Full text views

Total number of HTML views: 1
Total number of PDF views: 1 *
Loading metrics...

Abstract views

Total abstract views: 70 *
Loading metrics...

* Views captured on Cambridge Core between September 2016 - 26th May 2017. This data will be updated every 24 hours.