The balanced polymorphism hypothesis for the RS locus implies that RS − − and RS + + genotypes differ for risks of particular strengths and weaknesses. The predictions summarised in Figure 11.1 suggested that RS + + genotypes have strong left hemisphere advantages, but also strong risks of right hemisphere disadvantages. This chapter seeks to clarify what the latter might be. The main research strategy is to ask whether certain positive skills are associated with a high frequency of left-handedness. These may be clues to advantages for RS − − genotypes relative to risks for RS + + genotypes. The converse question, what are the risks for RS − − compared with advantages for RS + + will be asked in the next chapter.