**Subjects** <br> We will aim for usable data from 100 subjects per condition, for a total of 400 subjects after exclusions. We will recruit 600 subjects. Subjects will be recruited through Amazon's Mechanical Turk service and will receive $0.10 in exchange for completing the experiment. Subjects will be required to have a 95% HIT approval rate and to be based in the US, consistent with prior experiments in this study. **Stimuli** <br> The stimuli consist of eight objects presented against a light blue (#58ACFA) background measuring 666 x 546 pixels. Half of these objects are gray (#808080) rectangles measuring 64 x 32 pixels. The other half are 16 pixel-radius gray circles. A blue (#0000FF) fixation square measuring 11 x 11 pixels is positioned in the center of the display. The unexpected object is a dark gray (#404040) rectangle that can either be vertical (64 x 32 pixels) or horizontal (32 x 64 pixels). **Condition Assignment** <br> There are four possible conditions resulting from the combinations of attended set (2) x unexpected object orientation (2). Upon starting the experiment, the script counts how many subjects have completed the study so far and takes that number modulo 4. Each number 0-3 corresponds to one of the attended object x unexpected object color combinations. **Procedure** <br> A demonstration of the task may be viewed [here][1]. After accepting the HIT on Amazon's website, subjects will be redirected to an external website running the experiment in Javascript. _Instructions._ Subjects are instructed that they will see a set of objects move and bounce around, and that they will be asked to track one group of these objects and count how many times they bounce off the sides of the display window. <br> _Noncritical Trials._ Two trials. Subjects are told which set of objects, rectangles or checkerboards, they should monitor; they are also instructed to keep their eyes fixed on the blue square in the center. Then the trial begins, and the rectangles and checkerboards bounce (roughly 5-8 times per object) around the display at randomly varying velocities for 17 seconds. Objects always pass behind the fixation square. Subjects are asked to enter the number of bounces they counted after each trial. <br> _Critical Trial._ The critical trial proceeds just like the noncritical trials. After 5 seconds, the unexpected object appears and travels across the experiment window from right to left, passing behind the fixation square. It remains on screen for 6750 ms. The trial terminates after 17 seconds total. Subjects are asked to report their count, and then are asked whether they saw an additional object that had not been present on the previous trials. Then they are asked to select the shape and color of the object from a set of pre-determined options, or to guess if they did not notice anything. <br> _Demographic Questions._ Subjects are asked to select their age range, gender, whether their vision needs correction and if they were wearing it during the experiment, the status of their color vision, the number contained in Ishihara Plate 9, whether they experienced any problems with playback, and whether they had prior experience with a similar inattentional blindness task. After submitting their final response, subjects are presented with a completion code and told to return to Mechanical Turk to enter the code and receive payment. [1]: http://simonslab.com/mot/shades_demo.html