Approximate Number Sense Test

1. Stimuli and trials

1. Program the experiment in Psychopy, MATLAB, or something similar (a free version can also be downloaded for non-commercial uses at www.panamath.org).
2. Design all trials in the experiment to look more or less the same.
   1. Divide the display in half. Use a grey background.
   2. One side of the display shows a collection of blue circles.
   3. The other side shows a collection of yellow circles.
3. Draw the circles in different sizes, as shown in the sample trial (Figure 1).
   
   Figure 1. Schematic depiction of a single trial of the approximate number sense test. On each trial, the participant reports whether he saw more blue or yellow dots.
4. The key manipulation involves the number of yellow and blue circles. There should always be more of one kind than the other. The difference should be characterized in terms of a ratio: 2:1, 1.75:1, 1.5:1, 1.35:1, 1.25:1, and 1.15:1.
5. Instruct the program to produce 20 trials with each ratio.
   1. Randomly select the larger color.
   2. Randomly select the smaller number of circles.
   3. Select the larger number to make the desired ratio.
   4. Draw yellow circles on one side of the display.
   5. Draw blue circles on the other side.
   6. Randomly choose the radius of each circle between 1° (of visual angle) and 3.5°.
6. On each trial, a display appears for 500 ms. After it disappears, the participant presses the ‘Y’ key if they think they saw more yellow dots, or the ‘B’ key if they think they saw more blue dots.
7. Provide feedback after each trial with a screen that displays either “Correct!” or “Incorrect.”