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. 2018 Oct 15;8:15237. doi: 10.1038/s41598-018-33567-9

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© The Author(s) 2018

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

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Second-order orientation stimulus: behavioral tasks and performance. (a) Second-order orientation stimulus. A 2D uniform distribution centered at zero was added to a base luminance (c) to generate a white noise stimulus. The same 2D uniform distribution was modulated by a 2D sinusoid and added to a base luminance to generate a second-order orientation stimulus. The orientation seen in the stimulus is second-order, because it is based on the local contrast of the bands of the grating without any difference in the local mean luminance of the bands of the grating. (b–d) All task conventions were the same as in Fig. 1, except that the peripheral stimuli were second-order orientation patches rather than visual motion patches. (e) Block Design: All three tasks were presented in a block design identical to that used in the motion version of the task (Fig. 1).