Do we perceive the world differently if we need to evaluate our percept? - an EEG study Jessica Knoetzele , Joos, Ellen; Kornmeier, Juergen (Perception And Cognition Group, Institute for Frontier Areas of Psychology and Mental Health, Freiburg, BADEN WUERTTEMBERG Germany) C4
The information available to our senses is limited and to varying degrees ambiguous, making multiple interpretations possible. Our perceptual system has to construct the most probable interpretation to provide stable and reliable percepts. Depending on the sensory information's quality, this perceptual decision can become difficult. Moreover, the reliability of such a perceptual decision can also vary considerably. Recent studies indicate the existence of a meta-perceptual evaluation system, rating the reliability of perceptual decisions. In the current study, we investigated, whether the necessity to explicitly report the reliability of a perceptual decision changes processing of the observed stimulus. We presented ambiguous and unambiguous Necker lattices in random order. In Condition 1, participants indicated the perceived 3D lattice orientations. In Condition 2, participants reported in an additional second response the confidence of their perceptual decision. Reaction times are overall longer in condition 2 (with confidence report) compared to condition 1 (without confidence report). Further, already 100 ms after lattice onset the ERP amplitudes start to differ between conditions 1 and 2. This amplitude difference is reflected in an occipital difference starting at 104 ms (E1), a frontopolar component at 172 ms (E2), a parietal P300-like signal at 324 ms (E3), and a temporally sustained positivity lasting for more than 400 ms (E4). The a priori knowledge about a second evaluation task in condition 2 may amplify visual processing units (E1). Perceptual decision and top-down evaluation steps may start immediately after the lattice-gestalt construction, at 172 ms (E2). The evaluation result needs to be kept in working memory until the evaluation response, 1600 ms after stimulus onset (E4). In summary, the necessity to rate our perceptual decisions starts to alter perceptual processing remarkably early and slows down perceptual processing. We seem to perceive the world differently if we need to evaluate our percepts or to say it in terms of quantum cognition: Measuring the perceptual system's outcome changes its functioning.