Not Every Angle
Your sense of tilt is several times finer near vertical than it is at forty five degrees. Not today, not because you are tired. Always. This measures the size of it on your own eyes.
Two round patches of stripes, side by side, for four tenths of a second. One of them is rotated a little further clockwise than the other. Your job is to say which one, every time.
Half the pairs sit near vertical or horizontal. Half sit near the diagonals. Same difference in tilt, same patches, same second of viewing. The only thing that changes is where on the circle the pair happens to be sitting.
The tilt difference goes down to a degree and a half, which is the width of a pencil line held at arm's length. You will get some of those wrong, and that is the measurement, not a failure.
- 0️⃣ Three practice pairs with the answer shown afterwards, so the question is unambiguous before anything counts.
- 1️⃣ Forty eight pairs, shuffled. Four tilt differences, six pairs each in each of the two classes.
- 2️⃣ One question every time: which patch is further clockwise. Arrow keys work, and so do F and J.
- 3️⃣ Guessing scores fifty percent, so the curve tells you where guessing stopped.
- 4️⃣ The headline is a ratio: the smallest tilt you can call on the diagonals, divided by the same number at vertical.
- 🔬 Nothing here is drawn. A pixel grid has its own vertical and horizontal, and a rasteriser would hand you a fake cardinal advantage. Every patch is computed pixel by pixel from a cosine, so no orientation gets a crisper representation than any other.
- 🎯 The headline is a ratio of two numbers measured on the same eyes, same screen, same minute. Your distance, your display and your patience sit in both and cancel.
- 🎲 The reference orientation is jittered a few degrees on every single pair, so no exact alignment ever repeats.
- 🪞 Which side carries the further clockwise patch is random, and how often you pressed left is printed with your result.