**Piloting** <br> We piloted a total of 67 subjects according to the procedure outlined [here][1]. These data will not be analyzed with the data collected from the main experiment; their purpose was to ensure that the task functioned correctly, that the analysis script worked, and to get an estimate of how much data we could expect to exclude to better determine how many subjects to collect. **Subjects** <br> We will aim for usable data from 100 subjects per condition, for a total of 400 subjects after exclusions. Results from our pilot suggest that we can expect to exclude approximately 25% - 40% of all data collected; as such, 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 only be able to access the HIT if they are based in the US and have a HIT approval rating of at least 95% (that is, at least 95% of the HITs they submit end up being approved). **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) squares measuring 60 x 60 pixels. The other half are squares of the same size with a black (#0000000) and white (#FFFFFF) checkerboard pattern consisting of 25 square cells each measuring 12 x 12 pixels. Half of the checkerboards begin the patter with a black square in the upper left corner, and the other half begin with white. A blue (#0000FF) fixation square measuring 11 x 11 pixels is positioned in the center of the display. The unexpected object is either a 60 x 60 black and white checkerboard consisting of 16 cells, each 20 x 20 pixels, randomly assigned to one of two patterns (black in upper left or white in upper left), or a 60 x 60 square tessellation formed from 16 triangles (30 pixel base, 15 pixel height) randomly assigned to one of two possible color layouts. The triangles are arranged such that no two contiguous triangles share the same color. **Condition Assignment** <br> There are four possible conditions resulting from the combinations of attended set (2) x unexpected object type (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][2]. 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, squares 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 squares 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 something 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]: https://osf.io/2bsnr/ [2]: http://simonslab.com/mot/checker_demo.html