A demonstration of the experiment, exactly as a subject would experience it but without any data collection, can be viewed [here][1]. **Subjects** <br> We will aim for usable data from 100 subjects per condition, for a total of 400 subjects after exclusions. Results from a previous study suggest that we can expect to exclude approximately 30 - 40% of all data collected; as such, we will recruit 600 subjects. Subjects will be restricted to US residents. In a pilot experiment, 78% of all non-US workers had to be excluded (largely due to self-reported technical issues), while only 23% of US workers had to be excluded. Subjects will be recruited through Amazon's Mechanical Turk service and will receive $0.30 in exchange for completing the experiment. **Stimuli** <br> Because subjects will complete the experiment on their own devices, screen size and viewing distance cannot be controlled. Distances are therefore given in pixels. After the instruction screen, the game loads and begins to run. The interactive part of the display consists of a dark gray (#777777) "road," 600 x 500 pixels, between two medium gray "sidewalks" (#c1c1c1) on the far left and right, 150 x 500 pixels. On the left sidewalk is a 220 x 220 pixel image of a cartoon basket of seeds, and on the right sidewalk is a 220 x 220 pixel image of a cartoon barn. The player controls a purple (#800080) pentagon, oriented so that it points either right or left depending on which direction the player can travel, 40 pixels high and 40 pixels wide from edge to point that moves at 180 pix/s. Blue (#0000FF) triangle "pedestrians" (30 pixel base, 30 pixel height) spawn once every 400 ms, positioned randomly within the sidewalks, and travel either top-to-bottom or bottom-to-top at a randomly chosen speed of either 60 pixels per second or 120 pix/s. There can be up to 10 pedestrians onscreen at once. At the same time, red (#FF0000) circle (22 pixel radius) "cars" spawn continuously in the road, traveling top-to-bottom at a randomly chosen speed of 60, 120, 180, or 240 pix/s. There can be up to 10 cars onscreen at once. If the player has picked up a seed, a small circle (8 pix radius) of a randomly-chosen color (#FFD700, #F08080, #FFA07A, #20B2AA, or #87CEFA) appears on their avatar. When they transport a seed to the barn, a flower (100 x 100 pix) of the same color as the seed appears underneath the barn for 4 seconds. The unexpected object is a green (#008000) 40 by 40 pixel diamond. In the top-left corner of the screen is a counter displaying how many flowers are left to plant, and in the top-right is a score counter that increments each time the player deposits a seed. **Condition Assignment** <br> Subjects can be assigned to one of four conditions, each of which corresponds to a possible unexpected object location (near and in front; near and behind; far and in front; or far and behind). Subjects are assigned uniformly at random to these conditions. **Procedure** <br> After accepting the HIT on Amazon's website and having their worker ID confirmed as new by TurkGate [(Goldin & Darlow, 2013)][2], subjects will be redirected to an external website running the experiment in Javascript. _Instructions._ <br> Subjects are given the following instructions: <br> >You will be playing a game! Please close all other browser windows to make this game run as smoothly as possible. >You will control a purple shape with the left and right arrow keys. This shape only moves in one direction at a time and points in the direction it can go. If it's pointing left, you can move left with the left arrow key only. If it's pointing right, you can move with the right arrow key only. >You will start on the sidewalk next to a basket of seeds. Touch the basket to pick up a seed and carry it across the road to the farm on the other side to plant it. >You are safe on the sidewalks, but if you get hit by a car while trying to cross the road, you'll be sent back to the sidewalk you started crossing from and will have to start your crossing over again. >The faster you carry a seed across the road, the more points you get. You'll have 5 flowers to plant in total. Try to score as highly as you can. Good luck! _Gameplay._ Once off the instruction screen, the game begins. Subjects start on the left side of the screen at a fixed vertical distance of 300 pixels (relative to the road), pointing towards the seed basket; they can only move right-to-left until they touch the seed basket, at which point their avatar points towards the right and they can only move left-to-right. Subjects "plant a flower" when carry a seed across the road and touch the barn on the opposite side. They earn points equal to 50000 divided by the number of ms they took to cross, or 1, whichever number is larger. They have to plant 5 flowers in total. If the come into contact with a car, their position is reset to the middle of the sidewalk from which they began crossing. The unexpected object appears at one of two possible, randomly-chosen points. It can show up on the 7th crossing, when subjects are carrying their 4th seed across the road, or on the 8th crossing, when they are returning to the seed basket to pick up the 5th and final seed. We thus randomize whether "in front" and "behind" corresponds to left and right or vice-versa. The probe spawns when the player crosses the midpoint (450 pixels) and shows up 113 pixels away in the near case or 338 pixels away in the far case. The probe spawns at the same vertical height as the player, and in the "in front" condition, the probe appears in the player's path in the direction it can move, and in the "behind" condition it appears behind the player, in the direction they cannot travel. The probe is visible for 2 seconds. _Unexpected Object Appearance Judgments._ After they finish the game, subjects are asked several questions about the unexpected object regardless of professed noticing: * Whether or not they noticed anything new that was not a game object * Whether the new object was moving * In which direction the object was moving * What color the object was * What shape the object was _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/game/crossing_demo.html [2]: https://github.com/gideongoldin/TurkGate/wiki/Installation