To determine that, you would need to decide what are the physical/functional facts about an experience or a feeling? Of course �happiness� and �sadness� are easy, assuming the signs are obvious (smiles, tears etc) and these are assumed by facial expressions. But how do we determine � as we do � that someone is smiling but is not happy. This can be through knowledge of the person and what they are experiencing, facial expression, or sometimes just a �feeling� that summink aint right. So when a girl asks her bloke, do you love me? And he says �yes�. Many factors would help her determine whether that was true, or whether she had any nagging doubts.
How could you verify her doubts, and the smiling sadness without the signs, when they are just human feelings/experiecens? Biotheology and the study of neurons tries to find the answers, sometimes it does, often it doesn�t. Can we all agree what love is? It is everything to everyone. There can be no doubt that love and a religious (subjective) experience are functions that involve neurons, but it is, so far, doubtful they could actually be �verified� as such. Just random brain patterns, which implies something is going on, but not what.
So what we have is qualia, with your qualophiles and your qualophobes. Depending upon a person�s persuasion, you can have those that believe the experience is a phenomenon � sometimes a religious one - and those that just think brain matter is playing up, feeding imagination, or just misinterpreting signals. Sometimes though, attempts at verification is presented in physical form, like a smile or a kiss, some flowers etc. or for religious experiences, things like apparitions experienced by many at once, stigmata and miracles. True verification � in proving these things have actually happened as phenomena or subjective experience - is virtually unfeasible.