Higher Octane gasoline is for higher compression engines (like sport bikes and sport cars) which compress the air/fuel mixture to a higher degree, thereby causing the vapors to explode/detonate prematurely, this is the knocking. The higher octane gas, which is more resistant to combustion, is recommended for use in these engines for that purpose, to resist the premature detonation/knocking. It doesn't help a lower compression engine, since the combustion resistance is not necessary.
Before I knew this, I would occasionally try the higher octane in my bike, and found that in cold weather, the bike was harder to start with the higher octane gas... probably due to its combustion resistant properties... I can't say for sure, but switching to 87 octane again, it would always start up fine.
So really nothing is gained by higher octane gas if your bike doesn't ping (pre-detonate) with the lower octane gas.