How do photons "decide"? I was reading that when horizontally polarized light hits a vertical Polaroid all the light is blocked out. But when the Polaroid is off the vertical, some but not all photons "decide" to jump into the new plane of polarization. Could this be a "road less traveled" kind of effect?
If a run of two or three photons make the jump then conditions are affected in such a way, that the next photon is less likely to make the jump. Then as one or more photons get blocked, conditions cool down a bit increasing the likelihood that another run of jumps will occur: a mechanism of so called "deciding".
 A: There is no such mechanism. The probability for a photon to pass through a polarizer at an angle $\theta$ is $\cos^2(\theta)$, regardless of what has happened before, and regardless of how many photons "at once" try to pass through it. As Bell's theorem tells us, the quantum world is really random (or non-local).
A: If that happened, we would be able to detect it by looking at correlations between successive photons' "decisions."
That is, suppose you represent each pair of consecutive photons (1 and 2, 2 and 3, 3 and 4, etc.) with $+1$ if they both made the same "decision" or $-1$ if one went through the polarizer and the other didn't. Take the average of these numbers for all pairs and call it $C$. If a run of photons making the same decision changed the probability for the following photons, $C$ would be greater than zero. In reality, it comes out to zero, meaning that each photon doesn't change its behavior depending on what the one before it did. So we have clear experimental evidence that this modification of probabilities doesn't happen.
