Abstract

Masking is defined as the change in threshold energy eT*(τ) of a test stimulus T induced by a masking stimulus M of energy eM as a function of the relative time τ of occurrence. Masking is maximum when T and M occur simultaneously. A slight decrease in threshold for tests preceding the masking impulse by about 0.1 sec was explained as an alteration in appearance of the subsequent masking flash by a “subthreshold” test flash. Impulse-contrast threshold eT*/eM was investigated for masking impulses M of seven different energies superimposed on five backgrounds B. The increases in test threshold caused by M and by B were found to be independent and a modified Weber’s law (adjusted contrast threshold Cδ*≈0.1) held approximately. This conclusion was supported in a supplementary investigation of Cδ* using a category-rating-scale method.

Impulse masking results were applied to predicting the masking peak at the onset of a long flash by treating the first 60 msec as an impulse. The lowering of thresholds of tests delayed in a long masking flash implied other detection mechanisms (e.g., temporal resolution). Theoretical predictions accounted for 94% and 97% of the variance in two relevant experiments, correctly predicting the effect of masking-flash duration and of background intensity.

In both steady and intermittent light, masking is attributed primarily to fast processes (time constant ≪1 sec) which presumably have a neural rather than a photochemical basis.

© 1965 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. W. S. Battersby and I. H. Wagman, J. Opt. Soc. Am. 49, 752 (1959).
    [CrossRef] [PubMed]
  2. W. S. Battersby and I. H. Wagman, Am. J. Physiol. 203, 359 (1962).
    [PubMed]
  3. R. M. Boynton, J. F. Sturr, and M. Ikeda, J. Opt. Soc. Am. 51, 196 (1961).
    [CrossRef]
  4. M. A. Bouman, Opt. Acta 1, 177 (1954).
    [CrossRef]
  5. B. H. Crawford, Proc. Roy. Soc. (London) B134, 283 (1947).
  6. G. Sperling, Science 131, 1613 (1960).
    [CrossRef] [PubMed]
  7. I. H. Wagman and W. S. Battersby, Am. J. Physiol. 197, 1237 (1959).
  8. H. D. Baker, J. Opt. Soc. Am. 43, 798 (1953).
    [CrossRef] [PubMed]
  9. H. D. Baker, M. D. Doran, and K. E. Miller, J. Opt. Soc. Am. 49, 1065 (1959).
    [CrossRef] [PubMed]
  10. W. S. Battersby, I. H. Wagman, E. Karp, and M. B. Bender, Arch. Neurol. 3, 24 (1960).
    [CrossRef] [PubMed]
  11. R. M. Boynton, Arch. Ophthalmol. II. 60, 800 (1958).
    [CrossRef]
  12. R. M. Boynton, Sensory Communication (John Wiley & Sons, Inc., New York, 1961), p. 739.
  13. R. M. Boynton, W. R. Bush, and J. M. Enoch, J. Opt. Soc. Am. 44, 56 (1954).
    [CrossRef] [PubMed]
  14. R. M. Boynton and G. Kandel, J. Opt. Soc. Am. 47, 275 (1957).
    [CrossRef] [PubMed]
  15. R. M. Boynton and N. Miller, Illum. Engr. 58, 541 (1963).
  16. R. M. Boynton and J. B. Siegfried, J. Opt. Soc. Am. 52, 720 (1962).
    [CrossRef]
  17. W. R. Bush, J. Opt. Soc. Am. 45, 1047 (1955).
    [CrossRef] [PubMed]
  18. G. L. Kandel, doctoral dissertation, University of Rochester (1958). Cited in R. M. Boynton.12
  19. J. W. Onley and R. M. Boynton, J. Opt. Soc. Am. 52, 934 (1962).
    [CrossRef] [PubMed]
  20. L. L. Holladay, J. Opt. Soc. Am. 14, 1 (1927).
    [CrossRef]
  21. B. H. Crawford, Proc. Roy. Soc. (London) B123, 69 (1937).
  22. W. A. H. Rushton, J. Opt. Soc. Am. 53, 104 (1963).
    [CrossRef] [PubMed]
  23. G. Sperling, J. Opt. Soc. Am. 53, 520 (1963).
  24. G. Sperling, presented at the Psychonomic Society, Washington University, St. Louis, September 1962.
  25. G. Sperling, J. Opt. Soc. Am. 52, 603 (1962).
  26. A. W. Volkmann, Sitzber. Kgl. Sächs. Ges. Wiss. (Leipzig), Math.–Phys. 11, 90 (1859).
  27. R. Dodge, Psychol. Bull. 4, 10 (1907).
    [CrossRef]
  28. D. Sayre, M. I. T. Radiation Laboratory Series, 19 (McGraw-Hill Book Co., Inc., New York, 1949), p. 195.
  29. Photo Research Corporation, 837 North Cahuenga Blvd., Hollywood, California.
  30. The test stimulus in this and subsequent experiments, though small, definitely is not a point source. As spatial position is not varied and as there are no boundaries near the test, it is probable that the observed test-threshold changes are quite similar (though not exactly equivalent) to those that would have been observed with a point test. Preliminary observations support this assumption.
  31. The pre-adaptation field used in Exp. 2 is larger than the one used in Exp. 1, but as both are substantially larger than the test, their masking effect is similar (see for example, Battersby et al.2).
  32. In an earlier investigation of chromatic interactions in masking, Bush17 failed to note a similar second peak. However, his masking stimulus (560 msec) and test (40 msec) were orders of magnitude longer than those used here.
  33. For a preliminary account of this experiment see G. Sperling, Am. Psychol. 17, 354 (1962).
  34. G. S. Brindley, J. Physiol. 147, 194 (1959).
  35. J. A. Swets, editor, Signal Detection and Recognition by Human Observers: Contemporary Readings (John Wiley & Sons, Inc., New York, 1964).
  36. J. P. Egan, A. I. Schulman, and G. Z. Greenberg, J. Acoust. Soc. Am. 31, 768 (1959).
    [CrossRef]
  37. J. A. Swets, W. P. Tanner, and T. G. Birdsall, Psychol. Rev. 68, 301 (1961).
    [CrossRef] [PubMed]
  38. D. J. Weintraub and H. W. Hake, J. Opt. Soc. Am. 52, 1179 (1962).
    [CrossRef] [PubMed]
  39. J. Nachmias and R. Steinman, J. Opt. Soc. Am. 53, 1206 (1963).
    [CrossRef]
  40. Actually, eT= 0.022eM was presented on catch trials as it was inconvenient to produce eT= 0 without informing the subject. This test stimulus contained about 15 the energy of the previously determined threshold. The identity of the observers’ distribution of responses to the “blank” and to the next-more-intense stimulus ultimately justified its use.
  41. A. Rose, J. Opt. Soc. Am. 38, 196 (1948).
    [CrossRef] [PubMed]
  42. A. Rose, Proc. I.R.E. 30, 295 (1942).
    [CrossRef]
  43. Hl. de Vries, Physica 19, 553 (1943).
    [CrossRef]
  44. M. H. Pirenne and F. H. C. Marriott, in Psychology: A Study of a Science, edited by S. Koch (McGraw-Hill Book Co., Inc., New York, 1959), Vol. I, pp. 288–361.
  45. See above section, Masking by Impulse Flashes, p. 546.
  46. No assumption is made about the time τ at which max eT*(τ) occurs.
  47. G. Sperling, Doc. Ophthalmol. 18, 3 (1964).
    [CrossRef]
  48. W. S. Battersby (private communication).
  49. C. H. Graham and E. H. Kemp, J. Gen. Physiol. 21, 634 (1938).
    [CrossRef]
  50. M. Keller, J. Exptl. Psychol. 28, 407 (1941).
    [CrossRef]
  51. W. R. Biersdorf, J. Opt. Soc. Am. 45, 920 (1955).
    [CrossRef] [PubMed]
  52. R. M. Herrick, J. Comp. Physiol. Psychol. 49, 437 (1956).
    [CrossRef] [PubMed]
  53. H. B. Barlow, J. Physiol. 141, 337 (1958).
  54. H. R. Blackwell, J. Opt. Soc. Am. 53, 129 (1963).
    [CrossRef] [PubMed]
  55. Onley and Boynton’s19 data show instances where increasing masking luminance does not produce increases in thresholds of tests which nominally occurred at 0.0 msec (coincidence of onsets). This result is more likely to have occurred at negative times (test flash preceding) than at 0.0.
  56. H. D. Baker, J. Opt. Soc. Am. 45, 839 (1955), p. 843.
    [CrossRef] [PubMed]
  57. See Ref. 14, p. 284; also Ref. 1, p. 758.

1964 (1)

G. Sperling, Doc. Ophthalmol. 18, 3 (1964).
[CrossRef]

1963 (5)

1962 (6)

R. M. Boynton and J. B. Siegfried, J. Opt. Soc. Am. 52, 720 (1962).
[CrossRef]

J. W. Onley and R. M. Boynton, J. Opt. Soc. Am. 52, 934 (1962).
[CrossRef] [PubMed]

W. S. Battersby and I. H. Wagman, Am. J. Physiol. 203, 359 (1962).
[PubMed]

G. Sperling, J. Opt. Soc. Am. 52, 603 (1962).

For a preliminary account of this experiment see G. Sperling, Am. Psychol. 17, 354 (1962).

D. J. Weintraub and H. W. Hake, J. Opt. Soc. Am. 52, 1179 (1962).
[CrossRef] [PubMed]

1961 (2)

J. A. Swets, W. P. Tanner, and T. G. Birdsall, Psychol. Rev. 68, 301 (1961).
[CrossRef] [PubMed]

R. M. Boynton, J. F. Sturr, and M. Ikeda, J. Opt. Soc. Am. 51, 196 (1961).
[CrossRef]

1960 (2)

G. Sperling, Science 131, 1613 (1960).
[CrossRef] [PubMed]

W. S. Battersby, I. H. Wagman, E. Karp, and M. B. Bender, Arch. Neurol. 3, 24 (1960).
[CrossRef] [PubMed]

1959 (5)

I. H. Wagman and W. S. Battersby, Am. J. Physiol. 197, 1237 (1959).

W. S. Battersby and I. H. Wagman, J. Opt. Soc. Am. 49, 752 (1959).
[CrossRef] [PubMed]

H. D. Baker, M. D. Doran, and K. E. Miller, J. Opt. Soc. Am. 49, 1065 (1959).
[CrossRef] [PubMed]

G. S. Brindley, J. Physiol. 147, 194 (1959).

J. P. Egan, A. I. Schulman, and G. Z. Greenberg, J. Acoust. Soc. Am. 31, 768 (1959).
[CrossRef]

1958 (2)

R. M. Boynton, Arch. Ophthalmol. II. 60, 800 (1958).
[CrossRef]

H. B. Barlow, J. Physiol. 141, 337 (1958).

1957 (1)

1956 (1)

R. M. Herrick, J. Comp. Physiol. Psychol. 49, 437 (1956).
[CrossRef] [PubMed]

1955 (3)

1954 (2)

1953 (1)

1948 (1)

1947 (1)

B. H. Crawford, Proc. Roy. Soc. (London) B134, 283 (1947).

1943 (1)

Hl. de Vries, Physica 19, 553 (1943).
[CrossRef]

1942 (1)

A. Rose, Proc. I.R.E. 30, 295 (1942).
[CrossRef]

1941 (1)

M. Keller, J. Exptl. Psychol. 28, 407 (1941).
[CrossRef]

1938 (1)

C. H. Graham and E. H. Kemp, J. Gen. Physiol. 21, 634 (1938).
[CrossRef]

1937 (1)

B. H. Crawford, Proc. Roy. Soc. (London) B123, 69 (1937).

1927 (1)

1907 (1)

R. Dodge, Psychol. Bull. 4, 10 (1907).
[CrossRef]

1859 (1)

A. W. Volkmann, Sitzber. Kgl. Sächs. Ges. Wiss. (Leipzig), Math.–Phys. 11, 90 (1859).

Baker, H. D.

Barlow, H. B.

H. B. Barlow, J. Physiol. 141, 337 (1958).

Battersby, W. S.

W. S. Battersby and I. H. Wagman, Am. J. Physiol. 203, 359 (1962).
[PubMed]

W. S. Battersby, I. H. Wagman, E. Karp, and M. B. Bender, Arch. Neurol. 3, 24 (1960).
[CrossRef] [PubMed]

I. H. Wagman and W. S. Battersby, Am. J. Physiol. 197, 1237 (1959).

W. S. Battersby and I. H. Wagman, J. Opt. Soc. Am. 49, 752 (1959).
[CrossRef] [PubMed]

W. S. Battersby (private communication).

Bender, M. B.

W. S. Battersby, I. H. Wagman, E. Karp, and M. B. Bender, Arch. Neurol. 3, 24 (1960).
[CrossRef] [PubMed]

Biersdorf, W. R.

Birdsall, T. G.

J. A. Swets, W. P. Tanner, and T. G. Birdsall, Psychol. Rev. 68, 301 (1961).
[CrossRef] [PubMed]

Blackwell, H. R.

Bouman, M. A.

M. A. Bouman, Opt. Acta 1, 177 (1954).
[CrossRef]

Boynton, R. M.

Brindley, G. S.

G. S. Brindley, J. Physiol. 147, 194 (1959).

Bush, W. R.

Crawford, B. H.

B. H. Crawford, Proc. Roy. Soc. (London) B134, 283 (1947).

B. H. Crawford, Proc. Roy. Soc. (London) B123, 69 (1937).

de Vries, Hl.

Hl. de Vries, Physica 19, 553 (1943).
[CrossRef]

Dodge, R.

R. Dodge, Psychol. Bull. 4, 10 (1907).
[CrossRef]

Doran, M. D.

Egan, J. P.

J. P. Egan, A. I. Schulman, and G. Z. Greenberg, J. Acoust. Soc. Am. 31, 768 (1959).
[CrossRef]

Enoch, J. M.

Graham, C. H.

C. H. Graham and E. H. Kemp, J. Gen. Physiol. 21, 634 (1938).
[CrossRef]

Greenberg, G. Z.

J. P. Egan, A. I. Schulman, and G. Z. Greenberg, J. Acoust. Soc. Am. 31, 768 (1959).
[CrossRef]

Hake, H. W.

Herrick, R. M.

R. M. Herrick, J. Comp. Physiol. Psychol. 49, 437 (1956).
[CrossRef] [PubMed]

Holladay, L. L.

Ikeda, M.

Kandel, G.

Kandel, G. L.

G. L. Kandel, doctoral dissertation, University of Rochester (1958). Cited in R. M. Boynton.12

Karp, E.

W. S. Battersby, I. H. Wagman, E. Karp, and M. B. Bender, Arch. Neurol. 3, 24 (1960).
[CrossRef] [PubMed]

Keller, M.

M. Keller, J. Exptl. Psychol. 28, 407 (1941).
[CrossRef]

Kemp, E. H.

C. H. Graham and E. H. Kemp, J. Gen. Physiol. 21, 634 (1938).
[CrossRef]

Marriott, F. H. C.

M. H. Pirenne and F. H. C. Marriott, in Psychology: A Study of a Science, edited by S. Koch (McGraw-Hill Book Co., Inc., New York, 1959), Vol. I, pp. 288–361.

Miller, K. E.

Miller, N.

R. M. Boynton and N. Miller, Illum. Engr. 58, 541 (1963).

Nachmias, J.

Onley, J. W.

Pirenne, M. H.

M. H. Pirenne and F. H. C. Marriott, in Psychology: A Study of a Science, edited by S. Koch (McGraw-Hill Book Co., Inc., New York, 1959), Vol. I, pp. 288–361.

Rose, A.

Rushton, W. A. H.

Sayre, D.

D. Sayre, M. I. T. Radiation Laboratory Series, 19 (McGraw-Hill Book Co., Inc., New York, 1949), p. 195.

Schulman, A. I.

J. P. Egan, A. I. Schulman, and G. Z. Greenberg, J. Acoust. Soc. Am. 31, 768 (1959).
[CrossRef]

Siegfried, J. B.

Sperling, G.

G. Sperling, Doc. Ophthalmol. 18, 3 (1964).
[CrossRef]

G. Sperling, J. Opt. Soc. Am. 53, 520 (1963).

For a preliminary account of this experiment see G. Sperling, Am. Psychol. 17, 354 (1962).

G. Sperling, J. Opt. Soc. Am. 52, 603 (1962).

G. Sperling, Science 131, 1613 (1960).
[CrossRef] [PubMed]

G. Sperling, presented at the Psychonomic Society, Washington University, St. Louis, September 1962.

Steinman, R.

Sturr, J. F.

Swets, J. A.

J. A. Swets, W. P. Tanner, and T. G. Birdsall, Psychol. Rev. 68, 301 (1961).
[CrossRef] [PubMed]

Tanner, W. P.

J. A. Swets, W. P. Tanner, and T. G. Birdsall, Psychol. Rev. 68, 301 (1961).
[CrossRef] [PubMed]

Volkmann, A. W.

A. W. Volkmann, Sitzber. Kgl. Sächs. Ges. Wiss. (Leipzig), Math.–Phys. 11, 90 (1859).

Wagman, I. H.

W. S. Battersby and I. H. Wagman, Am. J. Physiol. 203, 359 (1962).
[PubMed]

W. S. Battersby, I. H. Wagman, E. Karp, and M. B. Bender, Arch. Neurol. 3, 24 (1960).
[CrossRef] [PubMed]

I. H. Wagman and W. S. Battersby, Am. J. Physiol. 197, 1237 (1959).

W. S. Battersby and I. H. Wagman, J. Opt. Soc. Am. 49, 752 (1959).
[CrossRef] [PubMed]

Weintraub, D. J.

Am. J. Physiol. (2)

W. S. Battersby and I. H. Wagman, Am. J. Physiol. 203, 359 (1962).
[PubMed]

I. H. Wagman and W. S. Battersby, Am. J. Physiol. 197, 1237 (1959).

Am. Psychol. (1)

For a preliminary account of this experiment see G. Sperling, Am. Psychol. 17, 354 (1962).

Arch. Neurol. (1)

W. S. Battersby, I. H. Wagman, E. Karp, and M. B. Bender, Arch. Neurol. 3, 24 (1960).
[CrossRef] [PubMed]

Arch. Ophthalmol. II. (1)

R. M. Boynton, Arch. Ophthalmol. II. 60, 800 (1958).
[CrossRef]

Doc. Ophthalmol. (1)

G. Sperling, Doc. Ophthalmol. 18, 3 (1964).
[CrossRef]

Illum. Engr. (1)

R. M. Boynton and N. Miller, Illum. Engr. 58, 541 (1963).

J. Acoust. Soc. Am. (1)

J. P. Egan, A. I. Schulman, and G. Z. Greenberg, J. Acoust. Soc. Am. 31, 768 (1959).
[CrossRef]

J. Comp. Physiol. Psychol. (1)

R. M. Herrick, J. Comp. Physiol. Psychol. 49, 437 (1956).
[CrossRef] [PubMed]

J. Exptl. Psychol. (1)

M. Keller, J. Exptl. Psychol. 28, 407 (1941).
[CrossRef]

J. Gen. Physiol. (1)

C. H. Graham and E. H. Kemp, J. Gen. Physiol. 21, 634 (1938).
[CrossRef]

J. Opt. Soc. Am. (19)

J. Physiol. (2)

G. S. Brindley, J. Physiol. 147, 194 (1959).

H. B. Barlow, J. Physiol. 141, 337 (1958).

Opt. Acta (1)

M. A. Bouman, Opt. Acta 1, 177 (1954).
[CrossRef]

Physica (1)

Hl. de Vries, Physica 19, 553 (1943).
[CrossRef]

Proc. I.R.E. (1)

A. Rose, Proc. I.R.E. 30, 295 (1942).
[CrossRef]

Proc. Roy. Soc. (London) (2)

B. H. Crawford, Proc. Roy. Soc. (London) B134, 283 (1947).

B. H. Crawford, Proc. Roy. Soc. (London) B123, 69 (1937).

Psychol. Bull. (1)

R. Dodge, Psychol. Bull. 4, 10 (1907).
[CrossRef]

Psychol. Rev. (1)

J. A. Swets, W. P. Tanner, and T. G. Birdsall, Psychol. Rev. 68, 301 (1961).
[CrossRef] [PubMed]

Science (1)

G. Sperling, Science 131, 1613 (1960).
[CrossRef] [PubMed]

Sitzber. Kgl. Sächs. Ges. Wiss. (Leipzig) (1)

A. W. Volkmann, Sitzber. Kgl. Sächs. Ges. Wiss. (Leipzig), Math.–Phys. 11, 90 (1859).

Other (16)

G. Sperling, presented at the Psychonomic Society, Washington University, St. Louis, September 1962.

D. Sayre, M. I. T. Radiation Laboratory Series, 19 (McGraw-Hill Book Co., Inc., New York, 1949), p. 195.

Photo Research Corporation, 837 North Cahuenga Blvd., Hollywood, California.

The test stimulus in this and subsequent experiments, though small, definitely is not a point source. As spatial position is not varied and as there are no boundaries near the test, it is probable that the observed test-threshold changes are quite similar (though not exactly equivalent) to those that would have been observed with a point test. Preliminary observations support this assumption.

The pre-adaptation field used in Exp. 2 is larger than the one used in Exp. 1, but as both are substantially larger than the test, their masking effect is similar (see for example, Battersby et al.2).

In an earlier investigation of chromatic interactions in masking, Bush17 failed to note a similar second peak. However, his masking stimulus (560 msec) and test (40 msec) were orders of magnitude longer than those used here.

J. A. Swets, editor, Signal Detection and Recognition by Human Observers: Contemporary Readings (John Wiley & Sons, Inc., New York, 1964).

Actually, eT= 0.022eM was presented on catch trials as it was inconvenient to produce eT= 0 without informing the subject. This test stimulus contained about 15 the energy of the previously determined threshold. The identity of the observers’ distribution of responses to the “blank” and to the next-more-intense stimulus ultimately justified its use.

R. M. Boynton, Sensory Communication (John Wiley & Sons, Inc., New York, 1961), p. 739.

G. L. Kandel, doctoral dissertation, University of Rochester (1958). Cited in R. M. Boynton.12

M. H. Pirenne and F. H. C. Marriott, in Psychology: A Study of a Science, edited by S. Koch (McGraw-Hill Book Co., Inc., New York, 1959), Vol. I, pp. 288–361.

See above section, Masking by Impulse Flashes, p. 546.

No assumption is made about the time τ at which max eT*(τ) occurs.

W. S. Battersby (private communication).

See Ref. 14, p. 284; also Ref. 1, p. 758.

Onley and Boynton’s19 data show instances where increasing masking luminance does not produce increases in thresholds of tests which nominally occurred at 0.0 msec (coincidence of onsets). This result is more likely to have occurred at negative times (test flash preceding) than at 0.0.

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (16)

Fig. 1
Fig. 1

Schematic diagram of a three-field tachistoscope. Subscripts refer to the individual stimulus fields. ALS, adjustable light shield; FL, fluorescent lamp (end view); FM, front-surface mirror; L, gas-discharge flash lamp; LS, light shield; NDF, neutral density filter; R, reflecting surface; S, stimulus field; W, adjustable neutral density logarithmic wedge; W′, balancing wedge.

Fig. 2
Fig. 2

Electrical circuit for operating fluorescent lamps to produce rectangular pulses of light.

Fig. 3
Fig. 3

Oscilloscope traces of light pulses produced by Sylvania SDCW, 14W fluorescent lamps. Ordinate is the same for each trace; the time base has been reduced by 10× for right figure. The slight 60-cps ripple in right figure is an artifact.

Fig. 4
Fig. 4

Photometric calibration of gas-discharge lamps. The gas-discharge lamp illuminates the disk (illustrated at right) while the fluorescent lamp illuminates the concentric annulus. The time relation between the two flashes is illustrated at left.

Fig. 5
Fig. 5

Masking response eT*(τ) to a 250-msec flash. Lower figure illustrates procedure. First traces indicate time sequence of masking stimulus lM(t), lowest trace indicates test lT(tτ). The arrow and broken baseline indicate a variable time τ of occurrence of test. Spatial arrangement of stimuli is illustrated at far left; dashed outline of test indicates it is superimposed on masking disk. Upper figure illustrates results. Ordinate gives test threshold energy eT* in log units of attenuation relative to arbitrary reference. Abscissa gives time base τ relative to masking-stimulus onset (refer to lower figure). Positive times indicate test occurrences after masking-stimulus onset. The last seven data points at far right are the same as those at far left.

Fig. 6
Fig. 6

Masking responses eT*(τ) to three impulse flashes of different energies. Lowest figure illustrates procedure (see Fig. 5). Pre-adaptation field B terminated at −300 msec; masking impulse M occurs at time 0.0; time of test T is variable. Spatial arrangement of stimuli illustrated at far right, not to scale. Upper figures illustrate results. The dashed vertical line at time 0.0 indicates the masking flash. An increase in test threshold [eT*(M+B)>eT*(B)] is indicated by ordinate values greater than zero, a decrease [sensitization, eT*(M+B)<eT*(B)] is indicated by negative ordinate values. The short horizontal parallel lines (−75, −100, −125, −150 msec, observer SMS; −200 msec, observer MWH) indicate the range within which all three curves lie.

Fig. 7
Fig. 7

Masking by red and green impulse flashes. Lowest figure illustrates procedure and spatial geometry. (Pre-adaptation field B is not indicated.) Upper figures indicate thresholds. Bar markers indicate the scale. Each curve has been moved up or down an arbitrary amount. Spectral composition of the various masking–test-field combinations is indicated at right by color names (R = red, G = green).

Fig. 8
Fig. 8

Masking prior to a 10-msec flash. Lower figure illustrates procedure and spatial arrangement of stimuli. Pre-adaptation stimulus terminated at −300 msec is not indicated. Upper figure illustrates absolute thresholds eT*(τ) of five observers. Each curve has been displaced up or down an arbitrary amount for ease of comparison.

Fig. 9
Fig. 9

Comparison of four masking procedures. Spatial geometry of the stimulus is illustrated schematically at left. The temporal sequence is illustrated on the right. The left-to-right dimension represents time, the depth dimension represents spatial position along a diameter of the stimulus, and the vertical dimension represents luminance. The height of the test indicates its energy eT at threshold. (a) Defining conditions for impulse contrast, Cδ. (b) Defining conditions for threshold: masking response to an impulse M (“impulse response”). Four possible temporal positions are indicated for the test flash, but only one test occurs on a particular trial. Heights of the test increments are drawn proportional to their thresholds. Below, a graph of these test heights plotted against their time of occurrence defines the threshold-masking response eT*(τ) (see Fig. 6 for data). (c) Conditions for measuring contrast threshold against a variable background (see Fig. 10). (d) Conditions investigated by Boynton and Kandel. The effect of varying background luminance on eT* was determined (see Table I).

Fig. 10
Fig. 10

Test threshold as a function of masking-impulse energy and background luminance, data for two observers. Points with same background luminance are connected. The 41 pre-adaptation refers to a 0.25-sec field of 41 ft-L terminated 0.3 sec before masking flash. When points fall too close together to be graphed individually, the range is indicated by parallel horizontal dashes. Control-threshold levels (masking flash omitted) are indicated by the horizontal lines. The energies eM of the three masking impulses of Exp. 2 are indicated on the abscissa and the obtained test thresholds at simultaneity eT*(τ = 0) are indicated by crosses (see Fig. 6). The values of eT/eM corresponding to the average adjusted contrast threshold Cδ* of the data are indicated (for method of calculation see text and Fig. 11.)

Fig. 11
Fig. 11

Threshold changes induced by impulse masking flashes added to five different backgrounds. The ordinate is the logarithm of the increase in test thresholds in ft-L×msec {log[eT*(M + B)−eT*(B)]}; top scale refers to observer SMS; bottom to MWH. Points with same backgrounds are connected. Points for which the difference in thresholds is less than 40% (0.15 log units) are connected by dotted lines. Best-fitting line of unity slope is indicated.

Fig. 12
Fig. 12

Confidence of detection in three different backgrounds as a function of test energy eT. Masking flash energy eM was 72 600 ft-L×msec. Vertical bars (observers SMS,MWH) represent thresholds measured in Exp. 5 (see Fig. 10 and text for details.) The results of “catch” trials are plotted above Φ which has been displaced slightly to the left on the abscissa. Its true contrast is the same as for the adjacent set of connected data points. The ordinate values above Φ are based on 50 trials each, other points 10 trials each.

Fig. 13
Fig. 13

A sample of data obtained by category rating of near “threshold” stimuli. Background luminance is 0.37 ft-L. On the average, the energy difference between adjacent test ranks is 38%. Each point represents one judgment by observer MWH. The horizontal line separates “yes” (detection) from “no” (nondetection) judgments. The connected vertical lines represent the median test energy which elicited each judgment category of response.

Fig. 14
Fig. 14

Consistency of judgmental criteria. Data are shown for three observers. Each point represents the median energy of the tests (average of the three background conditions) which elicited each judgment category. Vertical bars divide “yes” (detection) and “no” (nondetection) judgments.

Fig. 15
Fig. 15

Effect of masking-stimulus luminance and duration on peak test threshold, max eT*(τ). Ordinate is logarithm of increase in test-threshold energy (mL×5 msec) induced by masking stimulus: log[max eT*(τ) − min eT*(τ)]. Abscissa is logarithm of masking-flash duration in msec×flash-luminance in mL, using effective duration of 60 msec for flashes of 60 msec or longer, it is ∫060lM(t)dt. Upper scale refers to observer IHW, lower scale to observer WSB. Equations of regression lines: IHW, logCδ* = −0.551+0.152 log eM, (r = 0.985); WSB, logCδ* = −0.830+0.190 × log eM, (r = 0.993). Best-fitting lines of slope one (not shown): Cδ* = 0.65 (IHW); Cδ* = 0.43 (WSB). Data from Battersby and Wagman (see Ref. 10, Fig. 4, p. 756).

Fig. 16
Fig. 16

Effect of masking-stimulus luminance on test threshold (test occurs at nominal +12.5 msec after onset of masking stimulus, see text.) Masking stimuli of apparent brightness equal to a comparison standard are coded with points of same shape, as indicated. Background pre-adaptation was varied from 1 to 1000 mL (Obs. JS) and from 1 to 8900 mL (Obs. JO). Points of equal brightness are arranged from left to right in order of increasing pre-adaptation luminance. Equations of regression lines (not indicated): JS, logCδ* = −1.0.20 + 0.011 logeM(r = 0.987); JO, logCδ* = −1.207 + 0.033 logeM (r = 0.985). Data from J. Onley and R. M. Boynton (see Ref. 19, p. 938).

Tables (1)

Tables Icon

Table I Comparison of test threshold luminances (mL) with the masking stimulus “on” lT*(M + B) and without the masking stimulus lT*(B). Bm = log[lT*(M + B)/lT*(B)] − 2.15 is Boynton and Kandel’s estimate of neural masking response. Masking response as calculated in text is given in the last column, log[lT*(M + B) − lT*(B)]. Masking stimulus = 38 mL, duration = 560 msec; pre-adaptation background B extinguished 280 msec before onset of M. Data from Boynton and Kandel (Ref. 14, p. 278), average of three subjects.

Equations (7)

Equations on this page are rendered with MathJax. Learn more.

e T = 0 - l T d t d λ
e M ( x , y ) = - l M ( x , y ) δ ( t ) d t .
C δ * = [ e T * ( M + B ) - e T * ( B ) ] / e M .
C δ * · e M = max e T * ( τ ) .
log e M             and             log [ e T * ( M + B ) - e T * ( B ) ]
max e T * ( τ ) = C ¯ δ * 0 60 l M ( t ) d t .
- δ ( t ) d t = 1.