### Demo A demonstration of the task, exactly as subjects would experience it but without data collection, is available [here.][1] ### Subjects We expect to exclude roughly 50% of the data we collect. In order to finish with the desired 250 subjects per condition in each of two conditions, we will recruit a minimum of 1000 subjects (due to the automated nature of subject recruitment, we may end up with slightly more than 1000 subjects). We will recruit and screen subjects automatically via Amazon's Mechanical Turk. In order to accept the HIT, subjects will have to be based in the US, have a HIT approval rating of 95% or higher, and have completed at least 100 HITs. Subjects also must not have done a previous experiment in the lab; we will screen for this using TurkGate. ### Materials and stimuli This experiment is programmed in Javascript and is hosted on an external website. The primary task is a multiple object tracking task. The display window is a 700 by 600 pixel rectangle with a mid-gray (#808080) background. A 10 x 10 pixel fixation square in centered in the display, made of a 6 x 6 black square with a white, 2 pixel-wide border. The fixation square is this always visible, even when the shapes in the display pass behind it. There are two sets of objects, one white and one black. Each set has a square (40 by 40 pixels), a triangle (50 pixel base, 50 pixel height), a diamond (56 pixel width by 56 pixel height), and a circle (46 pixel diameter). These objects can move between 66 and 198 pixels per second, and randomly increase or decrease their velocity by 66 pixels per second randomly every 300 to 1000 milliseconds (without exceeding 198 pixels per second or falling below 66 pixels per second). The unexpected object is a 40 by 40 pixel cross with 14 pixel wide arms that moves at 132 pixels per second when it is on screen. The unexpected object can come in one of 12 colors, the hues of which are equally spaced in 30 degree intervals in HSV space. The saturation and value amounts were fixed at 50%, and the hues used were 0, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, and 330: ![the 12 possible colors, shown on the full color wheel][2] ### Procedure Subjects are taken to the experiment after accepting the HIT on Mechanical Turk. An instruction screen informs them how to do the task, and which set of objects they should monitor during the task. Subjects are assigned to track either the white or black objects at random. The experiment proceeds to the tracking task. All objects remain stationary for 1 second to allow subjects to prepare, then move around randomly for 15 seconds. The objects occlude each other as they pass, but always pass behind the fixation square. After each trial, subjects enter their count of the bounces. The unexpected object passes through the display on the third trial. It travels at a fixed vertical distance in the middle of the display, passing behind fixation. The unexpected object emerges behind an invisible occluder set either 70 pixels in from the edge, in the 80% window size condition, or 280 pixels in the 20% window size condition. It disappears behind an invisible occluder on the other side of the display, positioned the same distance from the opposite edge. Whether the unexpected object travels left-to-right or right-to-left is random for each subject. The unexpected object always exits the display 2 seconds before the end of the trial, and so onsets at a different point in the trial. The 80% condition is visible for 5 seconds, and onsets 8 seconds into the trial. The 20% object is visible for 1.5 seconds, and onsets 11.5 seconds into the trial. Although the distance the object travels in the 20% is a quarter of what it is in the 80% condition, because the unexpected object emerges gradually from behind an occluder, there is a fixed period of time during which it is partially visible irrespective of the window size. The time in the 20% condition is therefore slightly more than a quarter of that of the 80% condition. ![The two exposure durations/spans][3] After subjects enter their count for the critical trial, they are probed for noticing. They are asked whether they noticed anything new on the previous trial, and then asked to use a color slider to make a color patch match the hue of the unexpected object (the saturation and value are fixed at the correct values). Subjects then report the unexpected object's shape by selecting an option from a drop-down menu. Subjects are then asked to indicate on a scaled-down version of the display where the object was when they first noticed it. Subjects then complete a series of demographic questions, questions about their vision, a digital version of the Farnsworth D-15 task, questions concerning how smoothly the task ran in their browser, and a question about prior inattentional blindness experience. At the end of the experiment, they are given a completion code they enter on MTurk to complete the HIT. [1]: http://simonslab.com/mot/temporal_mot_col_demo.html [2]: https://mfr.osf.io/export?url=https://osf.io/r7nqb/?action=download&mode=render&direct&public_file=False&initialWidth=848&childId=mfrIframe&parentTitle=OSF%20%7C%20color_wheel.png&parentUrl=https://osf.io/r7nqb/&format=2400x2400.jpeg [3]: https://mfr.osf.io/export?url=https://osf.io/bew4p/?action=download&mode=render&direct&public_file=False&initialWidth=848&childId=mfrIframe&parentTitle=OSF%20%7C%20ex3.jpeg&parentUrl=https://osf.io/bew4p/&format=2400x2400.jpeg