In this experiment, you'll be performing a memory and search task.

On each trial, you'll see a bunch of objects flash on the screen briefly. You'll have to remember these images and detect changes in them.

When the objects disappear, their positions will change. Then, they'll reappear, and you'll have to say which object changed. There will always be one object that is present in the second array but absent in the first!

Your job: Find which object changed as fast as possible.

Once you've found the object that changed, press SPACE on your keyboard (the space bar).

After pressing SPACE, the images will all change to large "X"s, and you'll use your mouse to click on the image that changed.

In other words, you'll search for the object that changed; once you find it, you'll press SPACE; and then you'll click on the object that changed.

Before we begin, we'll go over this more to be sure the instructions are clear.

Click the ENTER key on your keyboard to proceed!

Just to make sure the instructions are clear, we'll go through a simple example here.

Recall that your task is to find the thing that changed as quickly as possible.

On a real trial, the images will appear and disappear quickly. After the grid disappears, you'd be presented with an array of objects, and you'd try to find what changed as fast as you can.

Suppose this was the array of objects. Your job would be to remember those objects and detect any changes.

In a real trial, that array would appear and disappear quickly. Then, suppose this new array appeared.

Your job would be to find the object that changed. Once you've found that object, you would press SPACE. Then, all the locations that had images would change to be big "X"s, like this:

When these "X"s appear, use your mouse to click on the "X" that marks the object that changed (i.e., if the object in the top left corner was not present in the first array, but was in the second, click on the "X" in the top left corner).

Click on the correct "X" now. Then, a button will appear. Pressing that button will allow you to begin the real experiment.