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Plaid maskers revisited: asymmetric plaids




A large number of psychophysical and physiological experiments suggest that luminance patterns are independently analysed in channels responding to different bands of spatial frequency. There are, however, interactions among stimuli falling well outside the usual estimates of channels' bandwidths. Derrington & Henning (1989) first reported that, in 2-AFC sinusoidal-grating detection, plaid maskers, whose components are oriented symmetrically about the signal orientation, cause a substantially larger threshold elevation than would be predicted from their sinusoidal constituents alone. Wichmann & Tollin (1997a,b) and Wichmann & Henning (1998) confirmed and extended the original findings, measuring masking as a function of presentation time and plaid mask contrast. Here I investigate masking using plaid patterns whose components are asymmetrically positioned about the signal orientation. Standard temporal 2-AFC pattern discrimination experiments were conducted using plaid patterns and oblique sinusoidal gratings as maskers, and horizontally orientated sinusoidal gratings as signals. Signal and maskers were always interleaved on the display (refresh rate 152 Hz). As in the case of the symmetrical plaid maskers, substantial masking was observed for many of the asymmetrical plaids. Masking is neither a straightforward function of the plaid's constituent sinusoidal components nor of the periodicity of the luminance beats between components. These results cause problems for the notion that, even for simple stimuli, detection and discrimination are based on the outputs of channels tuned to limited ranges of spatial frequency and orientation, even if a limited set of nonlinear interactions between these channels is allowed.

Author(s): Wichmann, FA.
Pages: 57
Year: 2001
Month: March
Day: 0

Department(s): Empirical Inference
Bibtex Type: Poster (poster)

Digital: 0
Event Name: 4. T{\"u}binger Wahrnehmungskonferenz (TWK 2001)
Event Place: T{\"u}bingen, Germany
Organization: Max-Planck-Gesellschaft
School: Biologische Kybernetik

Links: Web


  title = {Plaid maskers revisited: asymmetric plaids},
  author = {Wichmann, FA.},
  pages = {57},
  organization = {Max-Planck-Gesellschaft},
  school = {Biologische Kybernetik},
  month = mar,
  year = {2001},
  month_numeric = {3}