the person’s skill in the task. Similarly, a function describing the skill of the group as a whole can be estimated from the group decisions. As was described by Bahrami: [*“In experiments (...) psychometric functions were constructed for each observer and for the dyad by plotting the proportion of trials in which the oddball was seen in the second interval against the contrast difference at the oddball location”*]{} (@Bahrami2010, Supplementary Materials, p. 3).

Various assumptions about the nature of within-group interactions during the joint decision-making process can be made. From these assumptions, we can derive theoretical relationships between the parameters of members’ functions and the parameters of the group function. These are the models of decision making. The correctness of each joint decision model can then be tested against empirical data.

@Bahrami2010 described and evaluated four such models. One was own, in which group members communicate their confidence in their individual choices. Another model stemmed from signal detection theory [@Sorkin2001]. If members know each other’s relative discriminatory ability (i.e., their psychometric functions), the group can make a statistically optimal choice. Thus, under certain conditions, we have an upper bound on group performance. The third model suggested that the dyad is 