Talk:Object substitution masking

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    Reviewer 1

    I think this is very thorough review of OSM. My minor comments are below: In the third paragraph, the sentence:"At the same time, it must be noted that the spatial relationship between the target and the four dots is critical for effective masking, since masking does not occur if the four dots are not centered in the same perceived location as the target (Lleras & Moore, 2003) or if the dots do not surround the target image (Jiang & Chun, 2001)" is misleading because Lleras & Moore found that what matters is the spatio-temporal relationship between mask and target, such that even if the mask (a single dot) is never presented at the location of the target, if observers perceive it to be the same object (because of apparent motion), then the single dot will mask the target, even at a new location. Also, Jiang & Chun did show masking when the dots where not at the target location. A good correction would be: "At the same time, it must be noted that the spatio-temporal relationship between the target and the four dots is critical for effective masking: the dots can mask the target, even if they never overlap with it, as long as participants perceive the dots as having moved from the target location to their current location (Lleras & Moore, 2003). Jiang & Chun (2001) also studied how the spatial arrangement of mask and target modulates the magnitude of the masking effect." Or something along those lines.

    In the psychophysical section: The second paragraph can be spelled out a bit more clearly. After "continuity between the target and mask displays". Add: " in other words, when participants perceive the mask as representing the same object as the target, albeit after undergoing some changes in its featural description". After "when object continuity is broken", insert "(i.e., when observers perceive mask and target stimuli as representing different objects in the world)", masking....

    Reviewer 2

    I absolutely concur with Reviewer 1's remarks about the thoroughness of, and excellent scholarship evident in, Jim Enn's article on object substitution masking. The article is astonishingly complete in its survey of the literature and laudably unbiased in its presentation of different perspectives on object substitution masking. It should serve as an excellent jumping-off point for any researcher interested in pursuing research on object substitution masking. The article is very well written and should be accessible to a wide range of readers, both expert and non-expert. Given that Jim Enns is one of the world's preeminent experts on this topic, not surprisingly, there are no apparent factual errors in this article. One can safely assume that it accurately represents the current state-of-the-art in the area of (object substitution) masking.

    I have only a few minor comments about the introductory paragraphs, which I found to be somewhat less accessible than the remainder of the article. (I have also made some truly minor editorial changes to the article that I will not detail here -- small typos here, missed punctuation there.)

    • Some of the language in the introductory paragraph struck me as perhaps unneccessarily technical for a lay audience. In particular, in the description of the methods employed to elicit object substitution masking, I would simply say that the entire display, including the masking dots, is flashed briefly; and later on, I would simply write that the shapes disappear but the dots remain visible for a little while longer.
    • I would clarify (for the sake of lay readers) that chance is 1/5 in the example shown because there are five different shapes and the subject's task is to report the shape of the target.
    • The last sentence of the first paragraph ("It is as if..."), I might preface with, "In the subjective experience of the participant, ..." Object substitution masking is a highly subjective experience (or, I should say, one of its key features is its characteristic subjective experience of the vanishing of the target; anyone who has participated in these studies will know what I'm talking about) -- as is consciousness, for that matter!
    • I found the remarks about spatiotemporal relationships in the third paragraph to be a little vague for readers not already familiar with the studies described. The current description merely alludes to the crucial factor of object-identity -- which is established by perceived spatiotemporal continuity -- but does not state explicitly that a displaced mask continues to be effective because it retains its identity with the dots in their original location. Also, as I understand the current findings on object substitution masking, as far as spatial separation is concerned, distance does not play a role only to the extent that the mask is still affiliated with "its" particular target. This observation is almost trivial; but I think it is important to be very clear about all the caveats to the statement that object substitution masking is, to some degree, independent of the distance between mask and target -- in contrast to other forms of masking. These caveats are growing increasingly "philosophical" (issues of spatiotemporal object continuity and such) and may elude lay readers without a more detailed explication.

    Reviewer 3

    The Scholarpedia article on object substitution masking (OSM) is one of the best introductions available on this topic, particularly taking into account its succinctness. I have only two suggestions for updating it. First, the definition for OSM is worded so that the following text about the first instances of introducing this experimental paradigm and phenomenon are not precise enough. Namely, there were earlier publications describing the method of presenting masking and maskable (target) parts of the image first simultaneously and then subtracting a part of the target defining image elements -- a simultaneous onset, asynchronous offset procedure. For example, in USA, Cohene and Bechtoldt used this method to show that the remaining part of the image can mask the object that was formed within the context of the full set of image elements (Cohene & Bechtoldt, 1974, 1975). Therefore, I suggest either to change the definition of OSM or to include references to earlier articles. Secondly, selective attention stands as the basic concept to explain OSM. However, it appears that when spatial selective attention is pre-cued to target location well ahead of the target-plus-mask display by central pre-cues (not from the location close to or at the target position), the OSM cannot be easily eliminated (Luiga & Bachmann, 2007). Thus it should be important to limit the variety of spatial selective attention which can help overcome OSM effects to the locally pre-cued mode of operation.


    Cohene, L.S., & Bechtoldt, H.P. (1974). Visual recognition as a function of stimulus offset asynchrony and duration. Perception & Psychophysics, 15, 221-226.

    Cohene, L.S., & Bechtoldt, H.P. (1975). Visual recognition of dot-pattern bigrams: an extension and replication. American Journal of Psychology, 88, 187-199.

    Luiga, I., & Bachmann, T. (2007). Different effects of the two types of spatial pre-cueing: what precisely is "attention" in Di Lollo's and Enns' substitution masking theory? Psychological Research, 71, 634-640.

    actions to Reader 3's comments

    Action 1 (edit to include the Cohene & Bechtoldt, 1974, 1975 refs) Mar07-08

    Common onset masking refers to the visual masking of one part of an image by another part of the same image that remains visible after the first part has been turned off (Bischof & Di Lollo, 1995; Cohene & Bechtoldt, 1974, 1975; Di Lollo, Bischof & Dixon, 1993). The specific combination of a four dot mask with common onset masking was introduced by Di Lollo et al. (2000)….

    Action 2 (edit to include the Luiga & Bachmann (2007) ref Mar07-08

    These findings were interpreted as evidence for two fundamentally different masking mechanisms: reduced visibility because of a disturbed object formation process in the first 100 milliseconds of processing, and reduced visibility because of an object substitution process that occurs when the display changes before spatial attention has become focused on a single object. However, four dot masking still occurs when attention is directed voluntarily, rather than aided by a cue with an abrupt onset, leaving it for future studies to establish exactly which aspects of spatial attention are critically involved (Luiga & Bachmann, 2007).

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