PsychoPy Task Design Notes

Display Coordinate

In PsychoPy, coordinates of stimuli are set in a plane with a maximum distance from center as 1 unit. After some testing, it appears that for a face display of size (0.25, 0.25) to be fully visible on screen, it cannot be more than 0.35 (approximately) units away from the center. Accordingly, the radius of the stimuli display circle is set at 0.35. With eight face displays in total, there should be two faces displayed along the x-axis (± 0.35, 0), and two faces displayed along the y-axis (0, ± 0.35).

Circle with center coordinates of (0, 0) and a radius of 0.35 can be expressed in this formula: (x-0)^2 + (y-0)^2 = radius^2 = 0.352 = 0.1225

To calculate the coordinates of the other four faces, the (x, y) solutions for the following formulas are calculated:

x^2 + y^2 = 0.1225

X^2 = y^2

The coordinates are (± sqrt[0.1225/2], ± sqrt[0.1225/2]), which rounds to (± 0.2474874, ± 0.2474874).

Counterbalancing

1. During the happy/angry task, one item is counterbalanced: whether participants will view the happy OR angry block first.

2. During the happy&angry task, one item is counterbalanced: whether “negative” OR “positive” will be presented on the left of the visual analog scale during participant response.

Scale

The scale is created in PowerPoint (file on Box SCP Lab/Studies/Robust Averaging/Psychopy). When exporting the images from PowerPoint, select export as PNG and scale the image as 2880*1620. This will create images that match the resolution of the current scales.