Just found an interesting summary of the discontinuity effect. The name makes me wonder, do these people get paid on the basis of the number of 'biases' and 'effects' they discover? I quote:

(the researchers) named this the discontinuity effect because behavior in groups seemed discontinuous with the characteristics of individuals...

Wow. Presumably, if groups and individuals did behave similarly, they would've found a 'continuity effect'? Or if the data were inconclusive, there would be an 'continuity inconsistency effect'? OK I'll stop now...

What's interesting, though, is whether this particular individual-group discrepancy (groups are less cooperative in a repeated prisoner's dilemma game)  could be defined as a kind of group polarisation. This kind of polarisation would then be called rationality polarisation. Now, imagine that one day, scientists will know all the behavioural dimensions in which polarisation occurs. Does that imply they would be able to predict group decisions based on the behavioural properties of and individual choices on a decision task?