are easiest to distinguish. A shadow that forms an important part of the hidden face may be obvious on one screen and less noticeable on another. Excessive brightness can reduce some differences between pale regions, while very dark settings can make shadow details harder to distinguish. This is another reason two people can have different experiences with exactly the same puzzle without the difference indicating anything significant about their intelligence.
Attention and fatigue can matter too. Someone who has spent a long time concentrating on a screen may overlook an
