Interesting question Bucky!
I think on a date eye contact is usually a signal of intimacy and interest. If you were in a meeting with your boss you might look at their chin or your shoes as a sign of submission, but people would never do this is in a date. On a date eye contact is more about intimacy, interest, rewarding good convesation, etc. Therefore I expect more eye contact in the successful case.
What else does eye contact signal? It also says something about interest in the topic. I do observe that when people lose interest they look away a lot on dates. But this could just mean I’m talking to much, or picked a bad topic. I think conversation style choices should be guided by a “host” mindset rather than a status mindset. Making the other person comfortable is your prime concern. But when your doing posture, speech speed, pacing personal information, or defining the relationship it might be the dominant concern.
What do you think Bucky?
I think that both effects are likely and that this will add noise to the measure.
Noise is my main concern about your experiment in general—with only 10 samples in each treatment any effect would have to be large to reliably show up. If you were doing a t-test with p<0.05 then you would need Cohen’s d of 1.3 to get a significant result. This would be the equivalent of PHTG having the effect of moving a median date to a 90th percentile date which feels unlikely.
Obviously you’re being sensible and not being frequentist but the underlying problem is still there—even if PHTG has a decent sized effect the experiment might not show it, or, worse, if PHTG makes things slightly worse it could show up as being good in your experiment.
I would suggest that you try to work out a power calculation (even just by setting up your planned calculation and plugging in some fake numbers to see what happens) - if PHTG is slightly harmful to your chances (say 20% decreased chance of getting a second date) what are the odds that the experiment will lead you to accept PHTG?
As an aside, have you read this on putanumonit? It presents an alternative to PHTG which you might find interesting.