Humans and animals are said to have binocular vision if they possess two spatially separated eyes, but with overlapping visual fields that together provide a coherent view of the external world. Two eyes offer a range of advantages over one—for example, a wider field of view, stereopsis, and binocular summation. To achieve stereopsis, the visual system detects disparities in the positions of objects in the two eyes. However, humans are also sensitive to interocular (between-eye) differences in dimensions other than position—for example, in contrast or hue (Cohn, Leong, & Lasley,
1981; Cormack, Stevenson, & Schor,
1991; Stevenson, Cormack, Schor, & Tyler,
1992; Yoonessi & Kingdom,
2009; Formankiewicz & Mollon,
2009; Malkoc & Kingdom,
2012; Jennings & Kingdom,
2016; Georgeson, Wallis, Meese, & Baker,
2016). Such differences have been termed interocular (de)correlations (Cormack et al.,
1991; Stevenson et al.,
1992), dichoptic differences (e.g., Yoonessi & Kingdom,
2009; Malkoc & Kingdom,
2012), and binocular luminance disparities (Formankiewicz & Mollon,
2009). Here we term them interocular differences (IDs). An ID in contrast or hue can generate an impression of luster, and several previous studies have argued that a luster cue enables the ID to be detected (Formankiewicz & Mollon,
2009; Yoonessi & Kingdom,
2009; Malkoc & Kingdom,
2012; Jennings & Kingdom,
2016). Some recent studies have suggested models for the detection of IDs in hue and in contrast, based on luster (Georgeson et al.,
2016; Jennings & Kingdom,
2016).