1) They are talking about "light-emitting books" and used iPads, so what they really did test wasn't E-Readers (with E-Ink screens), it was tablets/smartphones.
2)
the e-reader—which was turned up to maximum brightness—provided additional illumination.
Why wouldn't you let the participants choose a brightness they liked, keep track of it and see how that affects sleep.
Two things bother me about this:
1) They are talking about "light-emitting books" and used iPads, so what they really did test wasn't E-Readers (with E-Ink screens), it was tablets/smartphones.
2)
Why wouldn't you let the participants choose a brightness they liked, keep track of it and see how that affects sleep.