Texture Discrimination

We do many experiments (both visual and auditory) aimed at figuring out what sorts of variations in physical energy are spontaneously discriminated by human observers.

In the visual realm, human observers spontaneously sense the differences between various sorts of texture.  One of our research goals is to determine the dimensions of human sensitivity to such texture differences.  We have empirically analyzed some specific classes of texture.  For example, we have done many experiments using randomly scrambled mixtures of different grayscales (Chubb, Econopouly & Landy, 1994; Chubb, Landy & Econopouly, 2004).  Textures in this class differ not in spatial structure but only in the relative proportions of different grayscales they contain.  As we have demonstrated, this space of textures is (like human color vision) perceptually three-dimensional.  Any two grayscale scrambles appear identical if they are equated in grayscale mean, grayscale variance and in one other statistic that we call “blackshot.”  Roughly speaking, the blackshot of a grayscale scramble is the proportion of its elements whose grayscale is very close to the blackest black.  It is possible to produce grayscale scrambles with dramatically different histograms whose physical differences pass completely unnoticed by human vision; all you need to do is make sure the two scrambles are equated in their mean, variance and blackshot.

In the auditory domain, we are currently conducting experiments analogous to the scramble experiments in order to analyze the dimensions of human sensitivity to tonal variations.  These experiments use rapid, random sequences of briefly windowed pure tones.  Here are some examples of the stimuli we use (called “twitters”). Major1 Major2 Minor1 Minor2

Additional References

  1. Drew, S., Chubb, C & Sperling G. (2010)
  2. Nam, J-H, Solomon, J.A., Morgan, J.M., Wright, C.E. & Chubb, C.  (2009)
  3. Chubb, C, Nam, J-H, Bindman, D.R., Sperling, G. (2007)
  4. Victor, J. D., Chubb, C., Conte, M. M. (2005)
  5. Chubb, C., Talevich, J. (2002)
  6. Nam, J-H., Chubb, C. (2000)
  7. Chubb, C., Nam, J-H. (2000)
  8. Chubb, C. (1999)