Fill in the blanks to complete the passage about economic games studies. Economic games studies have been criticized on issues of - validity. In particular, three concerns have been raised: (1) the money or item of worth used in these games is -; (2) being in a lab makes norms of - more salient; and (3) in lab studies, participants are acutely aware that their behavior is -, and thus they are much more likely to cooperate. cooperation "play" internal external scrutinized anonymous competition real