This is a rider provoked by the meritorious paper. It concerns the central issue – the origin and nature of the hypotheses triggering the predictive processing. Gregory (Reference Gregory2009) in his studies of illusions suggested that previous experience influences such hypotheses. Segall et al. (Reference Segall, Campbell and Herskovits1966) entertained this notion and tested proneness to illusions of cultural groups differing in experience of carpenteredness and openness of the environment, an approach followed by other cross-cultural researchers (Deręgowski Reference Deręgowski, Shapiro and Todorovic2017). There are, however, well known instances when the origin of the hypotheses does not quite match such paradigm. That is, rather than illusions illustrating the role of underlying hypotheses on producing the percept based upon expectations furnished by past experience, there are cases where the percept that arises from the illusion directly contradicts that to which we have become accustomed – even to the extent that we accept as our percept a form that violates known rules of perception. For example, the Necker cube fluctuates in depth, although the main depth cue it presents is that of oblique segments which can be seen as either receding to the left or to the right on the background of the paper, which furnishes no definite depth cues. Removal of this inert background does not remove the tendency to hypothesise, as the following observations concerning Zagloba's puzzle described below show.
A funnel looked into monocularly is seen for what it is: its converging walls receding towards the spout. After a short time, such percept changes spontaneously – perceptual inversion occurs and the funnel is no longer seen as a funnel, but as a tepee whose outer walls are the inner surface of the funnel and whose smoke outlet at the top is the funnel's spout (Deręgowski Reference Deręgowski2014). Moreover, if an insect, say a spider, were to walk from the rim of the funnel directly towards the spout, the direction of its journey would also be inverted, so that when walking downwards towards the spout it would appear to be walking upwards, but – and here is the rub – it would appears to grow smaller as it got closer to the observer. (Analogous observations apply to the spider walking towards the rim and the observer, it would on inversion appear to be moving away and yet to grow larger.) These apparent changes of perceived size are entirely contrary to the observer's daily experiences. Such violations in illusion are not unique to the example described above, with similarly nonsensical interpretations arising when we watch others walking around within Ames’ room (Ittelson Reference Ittelson1952) – they appear to grow taller or shorter as they move within it – or when we view Ames’ window (de Heer & Papathomas Reference de Heer, Papathomas, Shapiro and Todorovic2017) through which a rod has been placed at right angles to the trapezoidal window and observe that as the stimulus rotates, the window and the rod that transects it appear to counter-rotate in a way that they cannot. Although the perceptual mechanisms that underlie the above examples differ, they collectively question the notion that perceptual hypotheses are direct derivatives of experience, unless it can be accepted that such derivatives may not only be facsimiles of experience, but also experiences loosely conceived as enantiomorphs. If so, then the bounds of such “enantiomorphic” regions need to be defined.
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This is a rider provoked by the meritorious paper. It concerns the central issue – the origin and nature of the hypotheses triggering the predictive processing. Gregory (Reference Gregory2009) in his studies of illusions suggested that previous experience influences such hypotheses. Segall et al. (Reference Segall, Campbell and Herskovits1966) entertained this notion and tested proneness to illusions of cultural groups differing in experience of carpenteredness and openness of the environment, an approach followed by other cross-cultural researchers (Deręgowski Reference Deręgowski, Shapiro and Todorovic2017). There are, however, well known instances when the origin of the hypotheses does not quite match such paradigm. That is, rather than illusions illustrating the role of underlying hypotheses on producing the percept based upon expectations furnished by past experience, there are cases where the percept that arises from the illusion directly contradicts that to which we have become accustomed – even to the extent that we accept as our percept a form that violates known rules of perception. For example, the Necker cube fluctuates in depth, although the main depth cue it presents is that of oblique segments which can be seen as either receding to the left or to the right on the background of the paper, which furnishes no definite depth cues. Removal of this inert background does not remove the tendency to hypothesise, as the following observations concerning Zagloba's puzzle described below show.
A funnel looked into monocularly is seen for what it is: its converging walls receding towards the spout. After a short time, such percept changes spontaneously – perceptual inversion occurs and the funnel is no longer seen as a funnel, but as a tepee whose outer walls are the inner surface of the funnel and whose smoke outlet at the top is the funnel's spout (Deręgowski Reference Deręgowski2014). Moreover, if an insect, say a spider, were to walk from the rim of the funnel directly towards the spout, the direction of its journey would also be inverted, so that when walking downwards towards the spout it would appear to be walking upwards, but – and here is the rub – it would appears to grow smaller as it got closer to the observer. (Analogous observations apply to the spider walking towards the rim and the observer, it would on inversion appear to be moving away and yet to grow larger.) These apparent changes of perceived size are entirely contrary to the observer's daily experiences. Such violations in illusion are not unique to the example described above, with similarly nonsensical interpretations arising when we watch others walking around within Ames’ room (Ittelson Reference Ittelson1952) – they appear to grow taller or shorter as they move within it – or when we view Ames’ window (de Heer & Papathomas Reference de Heer, Papathomas, Shapiro and Todorovic2017) through which a rod has been placed at right angles to the trapezoidal window and observe that as the stimulus rotates, the window and the rod that transects it appear to counter-rotate in a way that they cannot. Although the perceptual mechanisms that underlie the above examples differ, they collectively question the notion that perceptual hypotheses are direct derivatives of experience, unless it can be accepted that such derivatives may not only be facsimiles of experience, but also experiences loosely conceived as enantiomorphs. If so, then the bounds of such “enantiomorphic” regions need to be defined.