Contrast amplification in global texture orientation discrimination.

Journal Article (Journal Article)

We show that adding a low-contrast texture stimulus that is far below its own detection threshold to an ambiguously oriented high-contrast texture can produce an easily perceived global orientation. When such a low-contrast (e.g., 0.1%) test texture and a high-contrast (e.g., 2%) amplifier texture are interleaved, the effective strength for global orientation detection closely approximates the product of the two contrasts. Therefore, adding two ambiguous textures, an amplifier texture at 5x its threshold contrast for global orientation discrimination and a test texture at 1/5x its threshold contrast, produces threshold global orientation discrimination, that is, 5x amplification of the below-threshold test texture. The observed 5x amplification factors are larger than facilitation effects reported in other pattern tasks. Amplification is 11x when orientation discrimination thresholds are compared to absolute detection thresholds. For second-order textures, maximum contrast amplification is about 2.5x. A contrast gain control model is presented that accounts for 90% of the variance in observed d' for texture patterns of differing geometries, exposure durations, and component contrasts. In the model, very low-contrast orientations are represented by power functions of their contrasts, with an exponent greater than two. As the contrast of an amplifier texture increases beyond about 4%, feed-forward gain control exerted by the amplifier ultimately nullifies the amplification effect and produces masking.

Full Text

Duke Authors

Cited Authors

  • Appelbaum, LG; Lu, Z-L; Sperling, G

Published Date

  • July 26, 2007

Published In

Volume / Issue

  • 7 / 10

Start / End Page

  • 13.1 - 1319

PubMed ID

  • 17997682

Electronic International Standard Serial Number (EISSN)

  • 1534-7362

Digital Object Identifier (DOI)

  • 10.1167/7.10.13


  • eng

Conference Location

  • United States