A comparison of forward and backward masking

Abstract

F i g. 2 . Racognitton t hre shol ds for forward and backward mask ing as a fun ction of masking sti muli and interstimulus in terv al s . circular pattern (visual angle = 65'). The masking stimuli, which were al so ne gative prints, transmitted an equal amount of luminance flux; their luminance was 4.2 ft L . The duration of the letters and masking stimuli was held constant at 2 msec .AteachISlemployed (5, 30 , 60 , and 100 msec .) the intensity of the letter was increased in 0.1 log unit steps by the useof Kodak neutral density filters until Ss correctly identified th e letter. Stimuli were presented to the dark adapted eye.Half of each session was devoted to FM, and the other half to BM, with the order reversed each day . Masking stimuli were r andomized in blocks of 8, ISIs in blocks of 4, with thresholds for 2 letters taken at each lSI per session . Over a period of 10 sessions 20 thresholds were obtained for each of the 24 cond itions. ResultsThe results for two Ss, illustrated in Fig. 2, show the following; (1) The amount of interference is greater with FM than with BM. Anal ysis of variance showed this difference to be significant beyond the .01 level. The data indicate that the differences are slight at the short ISIs but in crease with increasing lSI. The interaction between lSI and masking order was also significant for AbstractDifferences between forward and backward masking were studied by employing a disk, a r ing anda pattern as masking stimuli and letters a s test stimuli. The results show th at interferen ce is greater in forward than in backward masking. Interferen ce wa s found to decrease monotonically with increa sing interstimulus intervals (lSI) in all cases. Of the three masking stimuli, the ring produced the le ast interference and the pattern the most. Problem

Word superiority over isolated letters: The neglected case of forward masking

“…As discussed earlier, this finding is consistent with previous comparisons of the effects of forward and backward pattern masks (e.g., Kietzman et al, 1971;Michaels & Turvey, 1979;Schiller, 1966;Schiller & Smith, 1965;Smith & Schiller, 1966;Sperling, 1960Sperling, , 1965Turvey, 1973), which indicates that the different degrees of masking observed in Experiment 2 were not a quirk of that particular experiment. Moreover, as contemporary accounts of the WLP assign no special importance to particular exposure durations in backward-masked displays, there is no principled reason why the longer exposure durations necessitated by the use of forward pattern masks should detract from the finding that similar forms of the WLP were obtained under backward-and forward-masked conditions.…”

“…Previous research suggests that pattern masks are generally more disruptive in forward-masked displays (e.g., Kietzman, Boyle, & Lindsley, 1971;Michaels & Turvey, 1979;Schiller, 1966;Schiller & Smith, 1965;Smith & Schiller, 1966;Sperling, 1960Sperling, , 1965Turvey, 1973); a preliminary investigation of the forward-and backwardmasked displays planned for Experiment 2 revealed a similar difference between masking conditions. Specifically, when the same exposure durations were used for words and isolated letters in forward-and backward-masked displays, overall performance with forward masks was barely better than chance (55%), while performance with backward masks came close to perfection (96%).…”

Sensory registration and informational persistence.

“…Uncircled letters Rowl have employed a circle or ring to cue letter report (e.g., Di Lollo, 1978;Eriksen & Collins, 1964Eriksen, Collins, & Greenspon, 1967;Schiller & Smith, 1965); Kahneman (1968) has suggested that target energy may determine the form of the masking function produced by a circle mask, with high energy needed to obtain the U-shaped function found by Averbach and Coriell.…”

Parameters of visual simultaneity and of metacontrast and paracontrast of successively presented letters

“…"1 When the two stimuli are not equal in energy, monotonic curves are found. Metacontrast increases with both increasing intensity (Alpern, 1953;Schiller, 1966) and duration of S2 (the mask) (Alpern, 1953;Blane-Garin, 1966 and complernentarily with both decreasing luminance (Fehrer & Smith, 1962) or duration of S, (the target) (Alpern, 1953;Schiller & Smith, 1965;Blane-Garin, 1966. Paracontrast increases with the duration of S. (Blane-Garin, 1968).…”

“…Do metacontrast and paracontrast ha ve equal effects on letter perception? Though Eriksen and Collins (1965) and Eriksen (1966) assumed these effects were symmetric, most authors, since Stigler (1910), have found that metacontrast was more important than paracontrast when duration and luminance of S, and S2 were equal (Alpern, 1953;Schiller & Smith, 1965;Blane-Garin, 1966.…”