Priming effects definitely have a huge effect on initial PD play. In one experiment researchers phrased it as "the cooperation game" vs "the wall street game" a

Priming effects definitely have a huge effect on initial PD play. In one experiment researchers phrased it as "the cooperation game" vs "the wall street game" and saw much lower cooperation. In our case, however, we made the same people play for a month. I believe that learning effects strongly dominate priming over that time period.