Abstract
Studies have attempted to explain ambiguous states between complete awareness and unawareness by the notion of partial awareness (Kouider et al., 2010). This account proposes that access to some levels of representations in a hierarchy is independent of access to other levels, and that such access causes partial awareness. However, the account considering only the hierarchical access cannot explain partial awareness experienced in each level, especially gradually occurring phenomenal experiences in low levels. Here, we tested a hypothesis based on the parallel processing of spatial frequency (SF). Specifically, independent access to some SF information could cause gradual phenomenal experience in low levels. In two experiments we used a novel method in which a state of phenomenal experiences gradually changed for a long time. Stimulus displays were presented very briefly (about 12 ms per frame) and repeatedly with an inter-stimulus interval (ISI), ranging from 0 to 20 frames. As the ISIs increased, the probability of stimulus detection was lowered. Experiment 1a showed two superimposed sinusoidal gratings, each of which had a specific SF and orientation. Participants were asked to keep reporting the orientation of the gratings and showed that the duration of orientation detection over that of the stimulus presentation decreased with the ISIs but that the decrease was smaller for lower SF stimuli. Experiments 1b and 2 used more natural stimuli having broad SF spectrums, such as letters (a large E made of small Es) and scenes (dog, cat, car and truck pictures), respectively. We again found that participants detected poorly as the ISIs increased. However, this poor detection was lessened when the large Es and superordinate categories (animal vs. vehicle), requiring lower SF analysis, were reported. These results suggest that some SF information can be independently accessed, which may cause gradual phenomenal experiences in low levels of hierarchical representations.
Acknowledgement: This research was supported by the Brain Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (NRF-2017M3C7A1029658).