Luminance summation-contrast reduction as a basis for certain forward and backward masking effects

Abstract

The forced-choice recognition of forms presented at brief durations in a tachistoscope was impaired when a second field luminance occurred concurrently with the form presentation or at brief intervals before or after. The results support the temporal luminance summation hypothesis and its bi-directionality in time. ProblemEriksen & Hoffman (1963) have advanced a temporal luminance summation-contrast reduction hypothesis to account for certain cases of backward and foreward masking in vision. Due to the characteristic of the visual system to sum luminances over time intervals of nearly 100 ms., presentation of an illuminated field at short intervals prior to or following a field containing a form or a display, will have the effect of adding equal luminance to both the figure and ground of the display. This results in reduced figure-ground contrast 'with resulting impaired recognition of the display. Considerable evidence has supported the luminance summation hypothesis (Eriksen & Steffy, 1964; Steffy & Eriksen, 1965;Thompson, 1964) .Sperling (1963) has also reported that the presentation of a homogeneously illuminated (informationless) field at brief delays following a display impairs perception. He interprets the phenomenon in terms of an erasure process that wipes out the brief perceptual memory or storage of the display. He further uses this "erasure" concept in developing a more elaborate model of the perceptual system. Eriksen & Steffy (1964) have pointed out the inappropriateness on logical as well as experimental grounds of the erasure concept, but if it should be found that a homogeneously illuminated field that pre c e des a figure or display by a brief interval has the same impairment on perception as when it follows, the invalidity of an erasure concept would be selfevident. One cannot erase that. which is not yet present.The purpose of this experiment was: (a) to verify Thompson's (1964) findings with different techniques and methodology; and (b) to determine whether the luminance summation effect was symetrical, e.g., that the perceptual masking effect of an illuminated field was essentially the same when it preceded the stimulus at brief intervals as when it followed it. MetbodBy the use of a three field tachistoscope containing an adapting field (FA) and two stimulus fields (F I and F II), it is possible to demonstrate the luminance summation-contrast reduction effect in a straightforward manner. With the FA dark but containing a faintly lumi-

A comparison of forward and backward masking

“…Proof for this view is seen in the finding that th e masking effect is the same when the masking stimulus precedes the tes t stimulus a s when it follows it (Eriksen & Lappin, 1964) . However, this symmetry between forward masking (FM) and backward masking (BM) may not be a gen eral rule; the present study was therefore und ertaken to extend the r ange of conditi ons under which forward and ba ckward masking could be compa r ed .…”

Picture perception: Effects of luminance on available information and information-extraction rate.

“…In some masking experiments, target luminance has been varied (Turvey, 1973;Cheatham, 1952;Kinsbourne & Warrington, 1962a, 1962b and in others, mask luminance has been varied (Eriksen, 1966;Eriksen & Lappin, 1964;Loftus & Ginn, 1984;Spencer & Shuntich, 1970;Thompson, 1966). Irrespective of whether it is target or mask energy that is varied, performance has been found to increase with increases in target-mask energy ratio.…”

Rotating objects to determine orientation, not identity: Evidence from a backward-masking/dual-task procedure

“…Thus, we avoided random-dot masks, because they operate primarily at an early sensory (i.e., monoptic, possible retinal) level by stimulus degradation (Eriksen & Lappin, 1964;Kinsbourne & Warrington, 1962) and do not limit processing time (Turvey, 1973). We also avoided information masks, such as collages of superimposed objects, because these may interfere with recall (Bongartz & Scheerer, 1976).…”