Handedness in association with same-sex sexual attraction in Iran

Previous research has shown that same-sex sexual orientation is associated with differences in handedness. This study investigated this relationship by comparing Iranian cisgender gynephilic males (n = 239), cisgender ambiphilic males (n = 108), cisgender androphilic males (n = 314), transgender androphilic males (n = 103), cisgender androphilic females (n = 250), cisgender ambiphilic females (n = 96), cisgender gynephilic females (n = 32), and transgender gynephilic females (n = 123). Using a modified version of Edinburgh Handedness Inventory, we compared laterality index scores, rates of non-right-handedness, and extreme right-handedness between groups. Also, two features of handedness including its <i>direction</i> (i.e., the dominant hand) and <i>strength</i> (i.e., the degree of variability in preferring one hand over the other) were explored. We found that compared to gynephilic males, cisgender ambiphilic males had elevated non-right-handedness, and cisgender and transgender androphilic males had elevated extreme right-handedness. Our results indicated that right-handed cisgender androphilic males and females had greater strength compared to right-handed cisgender gynephilic males, while right-handed cisgender ambiphilic females and transgender gynephilic females had weaker strength compared to right-handed cisgender androphilic females. This study highlighted the importance of studying handedness direction and strength to understand underlying developmental factors influencing sexual orientation.