What is surprising is not that subjects are sensible to certain moral-social cues, but that such a simple cue (7 words) is sufficient. The more we know about each other, the less selfish we are.
This particular experiment doesn't really seem to have anything to do with increased knowledge, though. It's more a matter of framing: we reduce selfishness by cuing the 'responsibility' schema, so that giving is seen in a more positive light. I expect just two words would in fact suffice: "Stinginess test". Or, in the opposite direction, "Dupe test" -- I bet that title would reduce altruism dramatically.