Yet while those traits often helped badly governed companies, the Ferreira and Adams study suggests that increased monitoring can have a negative effect on well

Yet while those traits often helped badly governed companies, the Ferreira and Adams study suggests that increased monitoring can have a negative effect on well-governed businesses. That seems to be the key sentence. Although I am not certain, it seems likely that it is board interference with already effective management, not the presence of woman, that forms the causal link here.