Week 8. Are there differences between physical and filled-in surfaces?
– Definitely different, just problem of measurement. –
Hunjae Lee (VCC Lab)
Physical and filled-in surfaces are unlikely to be same when we consider the absolutely different stimuli; one is from physically external existence and another is kind of internal made image besides the debates about the mechanism or the stage of filled in. How could they are be same with this literally different premise? So if we cannot discriminate between them, it is probably due to the phenomenological sameness, for example, lack of awareness and also because of the pure measurement that cannot show the different quality between surfaces.
Although summing up the papers that are assigned in this week is not that helpful to answer this question, it can provide adequate explanation to why we cannot be aware the difference somehow. First of all Dennett’s idea that our brain doesn’t fill in but finding out omitted stimuli (so we don’t need to suppose representation of filled-in surfaces) turned to be wrong in spite of his provocative remarks. According to several studies there are representations for filled-in stimuli generated by the brain for sure (Yantis, 1998; Awater et al, 2005; Meng, 2005). Furthermore, the cortical distances in area V1 and V2/V3 for the blind-spot eye and fellow eye seems to be same, supporting active completion hypothesis as a mechanism of filling in (Awater et al, 2005). And ‘filling in’ looks like automatic, preattentive activity at the earliest stages of cortical processing with data show enhanced activities and neural filling-in in area V1/V2 (Meng, 2005). Filled-in surface that not only provokes representation but also shows automatically processing from early stages tempts us to think them identical.
However still is the possibility that they are different in some aspects. The average response latencies in V1 were ~12ms slower for stimuli presented to the blind-spot eye as compared with the fellow eye (Matsumoto & Komatsu, 2005), weak firing for blind spot at V1 but the stronger neural filling-in response in higher area such as V2 reflect that there are neural differences between physical and filled-in surfaces (Awater et al, 2005), whatever the mechanism is (top down or bottom up).
It is kind of a measurement. Simpler and better way to reveal the differences is to see behavioral differences with a specific task. Polat et al (2007) show subjective (c in Signal Detection Theory) and object aspects (d’ in SDT also) of filled-in surface that can vary with predictability of the task. It is needed to compare this result with the data from physical surfaces. My works on going inherited from former lab members is more concrete to see the different quality between them. For example, distracters that are in filled-in surfaces have less effect on detecting target compared with them in physical surfaces (Adopted from the class material of information processing theory, 2009). And the pilot data from the task that is try to discriminate the different ability of depth perception in periphery area raise the possibility that depth perception is somewhat possible with filled-in surfaces but more impared than physical surfaces. (See the supplement)
References
Dennett, D. (1992). Filling in versus finding out: A ubiquitous confusion in cognitive science, in Pick, Van den Broek, Eds. Cognition, Conception, and Methodological Issues. American Psychological Association.
Yantis, S. & Nakama, T. (1998). Visual interactions in the path of apparent motion. Nature Neuroscience, 1(6), 508-512
Awater, H., Kerlin, J. R., Evans, K. K., & Tong, F. (2005). Cortical representation of space around the blind spot. J Neurophysiol, 94(5), 3314-3324.
Meng, M., Remus, D. R., & Tong, F. (2005). Filling-in of visual phantoms in the human brain. Nature Neuroscience, 8, 679-685.
Polat, U. and D. Sagi (2007). The relationship between the subjective and objective aspects of visual filling-in. Vision Research, 47 (18), 2473-2481.
Matsumoto, M & Komatsu, H. (2005). Neural responses in the macaque V1 to bar stimuli with various length presented on the blind spot. J Neurophysiol, 93, 2374–238
Chong S.C. (2009). Blind spot: the class material of information processing theory, Yonsei University, Korea.
Supplement for Week 8. Are there differences between physical and filled-in surfaces?
Hunjae Lee (VCC Lab)
è Distracters that are filled-in have less effect on detecting target compared with them in physical surfaces. Adopted from the class material of information processing theory, 2009
è The upper line indicates ‘disparity condition’ while bottom line is ‘no disparity’. The task of participant was to report whether sinusoidal depth pattern has seen or unseen. And the data are below. (From Participant SC) d’ was higher in physical surfaces than blind spot.
References
Chong S.C. (2009). Blind spot: the class material of information processing theory, Yonsei University, Korea.