Purchase this article with an account.
Nicolaas Prins; Evidence for linear summation of information across orientation channels in texture perception. Journal of Vision 2007;7(9):971. doi: 10.1167/7.9.971.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Rotating an orientationally narrow-band texture is akin to increasing contrast in one ‘off-orientation’ channel while decreasing contrast in the opposing off-orientation channel. Varying the amplitude of rotation primarily affects the contrast amplitudes in the off-orientation channels, while the locations on the orientation continuum of the off-orientations remain relatively stable. As such, an orientation-modulated (OM) texture, in which alternating regions are rotated in opposite directions, contains four distinct contrast deviations relative to its unmodulated counterpart. Each of these four deviations could serve as a cue to detect the modulation. In the experiments reported here, textures were created in which the four cues are combined in a variety of ways. The cues were added to an unmodulated ‘base texture’. The addition of cues was performed in the Fourier domain, resulting in a lack of perceived transparency between the base texture and the added cues. Rather, an increase of contrast in one off-orientation channel, for example, leads to a perceived increase of overall contrast and a slight shift in the perceived global orientation in the texture region. Depending on the particular combination of cues, either the texture's overall orientation, overall contrast, or both are modulated. Results indicated that cues within the same orientation channel always sum linearly. It was also found, somewhat surprisingly, that cues sum linearly across orientation channels as well, but only when cues are combined such that the resulting texture is modulated in overall contrast. All other combinations lead to probability summation of cues. Finally, a difference between the naive, inexperienced observers and the author was observed, in that the author displayed probability summation of cues under all conditions. Control experiments explored the source of this observed difference.
This PDF is available to Subscribers Only