I'm really not up on what's going on, or has ever gone on, in determination of IQ measurement, so my comments are purely off the top of my head. What you've said sounds like an interesting concept, and I think IQ could be related to reaction time but perhaps not directly measured according to reaction time, because I think reaction time can also be affected by other variables, like emotional health or a person's general emotional state at the time of testing. Efficient decision making on a larger scale seems to me to be a result of a person's emotional health, so I wonder if it wouldn't also be related on a smaller scale as well.

The proposed reading/tone experiment would test a person's level of concentration, how well the person could focus. If the person had a jumpy temperament, then he/she would probably do poorly. Conversely, I've known people who grew up in small quarters with large families, which taught them very early how to block out distracting noises so they could concentrate. This may say something about their intelligence that they were able to do this, although someone who grew up in a smaller family in which this particular skill wasn't so important might never be able to block out distracting noises as well as the person from the larger family.

I'm sure there's much in what you've said that I'm missing, though. Please let me know what you think.