The observations not only suggest that you have free will (a useful thing to know in other, perhaps more earth-shaking situations), but reveal some additional interesting characteristics of this attribute.
There is some chance that when you first saw the figure together with the two buttons, you did not in fact immediately see the arrows pointing in the direction in which you had decided to see them pointing. What this indicates is that the power of free will does not extend to determining what you see; what you see at any given time is determined by actions of your brain which you cannot fully control (and of which you are not aware). What you were, however, able to do is to withhold action until you did see the arrows pointing in the direction you had previously chosen. What this indicates is that one part of your brain (the part that contains YOU) is capable of observing the variable inputs of another part of your brain (the part that is responsible for what you see) and deciding whether or not to act based on the perception offered at any given time. This may be a less potent "free will" than you might have wished tou had but, if you think about it for a while, its actually not bad at all.
That IS sort of interesting. Can we run through it again please?