Stimuli used in this study consisted of images of single objects (150 × 150 pixels for
Experiments 1,
3,
4, and
5, 55 × 55 pixels for
Experiment 2) and object ensembles (a collection of approximately 60 objects within an image; 378 × 378 pixels in size for
Experiments 1,
3,
4,
5, and
6; see
Figures 1 through
6). All of the single objects used were also present in all of the corresponding ensemble images. Images in
Experiments 1,
2,
3,
4, and
5 were constructed using stone beads made from semiprecious gems and photographed using a desktop studio set up (for more details, see Cant & Xu,
2012, experiment 4, and
Cant & Xu, in press). Stimuli were presented in two distinct shapes (a star or a heart for single objects and a collection of stars or hearts for ensembles) and also in two different textures (for single objects: individual surface textures taken from one of two different texture “families” that closely resembled each other; for object ensembles: a heterogeneous mixture of individual surface textures that belonged to one texture “family” and another mixture that belonged to a different, but visually similar, texture “family”). The two texture families were labeled as “texture A” and “texture B” to facilitate responses in the texture-discrimination task in both the single-object and ensemble conditions. For both single objects and ensembles, we used four different exemplars for each shape and texture combination (e.g., four different hearts from texture A, four different stars from texture A, four different hearts from texture B, etc.). The same two shapes and the same two stone textures were used in each experiment (with the exception of
Experiments 3 and
4 in which one new texture replaced one of the textures used in
Experiments 1,
2, and
5; see
Figures 3 and
4). The two shapes were chosen to be distinct to encourage the usage of a local-processing strategy wherein attention to a single object in the ensemble would be sufficient for the observers to successfully perform discriminations of ensemble shape. In contrast, the two types of textures were chosen to be similar to each other to encourage the usage of a global-processing strategy wherein attention to multiple objects in the ensemble would be required for the observers to successfully discriminate one stone texture from the other (with the exception of the textures used in
Experiment 5). All stimuli were presented in full color except for those used in
Experiments 3 and
4, which were presented in gray scale. Images in
Experiment 6 were created using Adobe Photoshop CS6 software (Adobe Systems, San Jose, CA) and MATLAB (Mathworks, Natick, MA). To encourage a global-processing strategy for ensemble shape, 10 unique exemplars of hearts and 10 unique exemplars of stars were created by warping the original heart and star shape contours used in
Experiments 1,
2,
3,
4, and
5. Additionally, five unique ambiguous “mixed” shapes were created and added to the ensembles to further create heterogeneity in ensemble shape perception and thus encourage observers to adopt a more global scope of attention when engaged in the ensemble shape discrimination task. The shape exemplars were filled with the same surface texture patterns used in
Experiments 1,
2, and
5. Furthermore, in
Experiment 6, we matched the hue of the ensembles across textures A and B using Photoshop, and the luminance histograms of the textures were equated using the SHINE toolbox extension for MATLAB (Willenbockel et al.,
2010). Luminance histograms were equated in a pair-wise manner in order to hold luminance constant between textures A and B but maintain heterogeneity of luminance within each ensemble image (see
Experiment 6 and
Figure 6).