– CB & AB is studying insufficient visual awareness, not whole consciousness. –
Hunjae Lee (VCC Lab)
In order to study consciousness, a good idea is finding a phenomenon that we fail to be conscious under certain circumstances. Both change blindness (CB) and attentional blink (AB) are such methods that reveal the limitations of human visual perception. CB and AB take advantages in this respect above. Suppose that we can divide our behavioral performance which reflects our conscious experiences into some stages below.
① Good performance with consciousness. |
② Bad performance with consciousness |
③ Not that bad performance with unconsciousness |
④ Bad performance with unconsciousness |
Table 1. Stages of behavioral performance
CB and AB are useful to reveal the characteristics of visual awareness via analyzing between ①② and ③④ / ① and ② / sometimes even ③ and ④. Because simple dichotomy, that is detecting T2 stimuli and change or not, helps us to understand the role of attention and the visual representation with capacity of visual working memory. We can hypothesize various theories of CB and AB and test it with manipulating the size, category, modality of stimuli, the time delay between T1 and T2, object complexities, number of items and so on. For example, approximately 500ms looks like a key of consciousness of T2 in AB (Shapiro, K.L. et al, 1997). And even though they regard consciousness as reportablity of stimuli, the difference neural activity between T2 missed as compared to no T2 trials tell us something about stage ③ and ④ (Kranczioch, C. et al., 2005).
But there are some obstacles of CB and AB to be solved. Besides difficulty of explaining ③, ④ in table 1, theorizing them to clarify our visual processing seems to be hard. The task performance of CB is vulnerable to subjectivity like expectation of the observer even though when the observer gives full attention to stimuli (Austin, E. L., & Enns, J. T., 2003). In the line with this result, the possibility that an expert for a certain stimuli can easily detect the change makes this problem more difficult. Even more, Zelinsky, G.(2003) raise another problem in theorizing CB. He argue that there is no critical study that defeat unlimited-capacity parallel model against bottleneck theories. I suggest that some studies about VWM which uses the parameter ‘similarity’ like (eg., Awh et al, 2007) need to be replicated with his method evaluating similarity directly between different stimuli.
Second, they cannot represent whole conscious experiences. Cross modal experiments with RSVP paradigm usually show AB not occurred. Considering auditory or tactile senses contribute to our fruitful consciousness, visual awareness is still not enough to explain it. Furthermore, more important problem is the fact that both memory and attention are not necessities of consciousness. Attention seems to be independent of visual awareness (Shin et al, in Press). And CB can be a kind of memory task, comparing two different stimuli, but we are sure conscious every moment.
References
Austin, E. L., & Enns, J. T. (2003). Change detection in an attended face depends on the expectation of the observer. Journal of Vision, 3, 64-74.
Awh, E., Barton, B., & Vogel, E. (2007). Visual working memory represents a fixed number of items, regardless of complexity. Psychological Science, 18, 622-628
Shapiro, K. L. et al. (1997). The attentional blink. Trends in Cognitive Sciences, 1, 291-296.
Kranczioch, C. et al. (2005). Neural correlates of conscious perception in the attentional blink. Neuroimage, 24, 704-714.
Shin, K., Stolte, M., & Chong, S. C. (in Press). The effect of spatial attention on invisible stimuli. Attention, Perception, & Psychophysics.
Simons, D. J., & Ambinder, M. S. (2005). Change blindness: theory and consequences. Current Directions in Psychological Science, 14, 44-48.
Zelinsky, G. (2003). Detecting changes between real-world objects using spatiochromatic filters. Psychonomic Bulletin & Review, 10, 533-555.