Down to tempo as much as anything.The ear doesn't really notice dissonances if they happening fast, but starts thinking about them and rationalising them in to the harmony if it has time to cogitate. Play your example sequence reaonably briskly, and you'll just hear a little melody floating over an A7 chord. Play it very slowly and heavily(particularly on six wind or bowed instruments or voices) and that F natural on the second beat will sound like some kind of augmentation of the chord.
A secondary factor is the ear accepts movement logical movement in a part as not implying harmony change(by logical movement I mean something with a pronounced pattern, eg a rising or falling scale, chromatic or diatonic for example).So in this case, because we have a rising chromatic scale, we dont feel the harmony is changing. Like if you play a C chord on a guitar, in a bum-ching bum-ching sort of way, and lower the bass as you go, C/B/A/G. Now, in conventional harmonic lingo, when you hit the A in the bass you might think you are playing an Amin7 chord. But you arent, really. Your ear will inform you you are still playing a C chord, just embellished with a walking bass line.
In general, what you've got there is an A7, I would say!