Could you point out specific articles?
There seems to be a lot about learners, evolution, and theory on that page, but actual measurements seem sparse. (Only 2 in the first 10 are even on this topic.)
One of the relevant links mentions:
> Empirical research on whether and how diversity is
actually related to work group functioning is limited, however,
and the evidence is mixed, depending in part on what kinds
of differences constitute the "diversity" in question (see Milliken
and Martins, 1996; Pelled, 1996, for reviews).
Researchers have examined the impact of diversity in identity
group memberships, such as race and sex (e.g., Cox, 1993;
Jackson and Ruderman, 1995); organizational group memberships,
such as hierarchical position or organizational function
(e.g., Bantel and Jackson, 1989; Ancona and Caldwell, 1992);
and individual characteristics, such as idiosyncratic attitudes,
values, and preferences (e.g., Hoffman, 1959; Meglino,
Ravlin, and Adkins, 1989; Bochner and Hesketh, 1994).
Although certain types of diversity appear to be beneficial,
studies focused on race and gender have demonstrated both
positive and negative outcomes (see Williams and O'Reilly,
1998, for review), suggesting that certain conditions may
moderate these outcomes. To date, however, most scholars
have only speculated as to what these conditions might be.
As a result, consultants and managers interested in diversity have had to rely largely on some combination of common sense and good faith for the rationales they advance about
why and how companies should address the issue.
(The other relevant link is a book, which doesn't have an abstract in the same sense.)