▁making ▁the ▁theory ▁un test able . ▁ ▁Over la pping ▁brain ▁variables ▁and ▁sexual ▁ar ous al ▁While ▁there ▁is ▁disag re ement ▁among ▁ne uro log ists ▁on ▁whether ▁or ▁not ▁it ▁is ▁possible ▁to ▁categor ically ▁distinguish ▁male ▁bra ins ▁and ▁female ▁bra ins ▁by ▁meas uring ▁many ▁variables ▁in ▁the ▁brain , ▁ne uro log ists ▁agree ▁that ▁all ▁single ▁variables ▁in ▁the ▁brain ▁display ▁more ▁individual ▁variation ▁and ▁overlap ▁between ▁the ▁sex es ▁than ▁differences ▁between ▁the ▁sex es . ▁For ▁instance , ▁men ▁and ▁women ▁al ike ▁are ▁capable ▁of ▁class ifying ▁sex ▁acts ▁as ▁sexual ▁no ▁matter ▁if ▁they ▁find ▁them ▁appe aling ▁or ▁not , ▁making ▁a ▁gen ital ▁response ▁to ▁un appe aling ▁er otic ▁stim uli ▁a ▁single ▁mechanism ▁step . ▁It ▁is ▁therefore ▁argued ▁by ▁ne uro log ists ▁that ▁category ▁specific ity ▁of ▁gen ital ▁response ▁to ▁er ot ical ▁imag ery , ▁being ▁determined ▁by ▁one ▁or ▁a ▁small ▁number ▁of ▁closely ▁linked ▁brain ▁mechan isms ▁and ▁therefore ▁not ▁subject ▁to ▁significant ▁mult ivari ate ▁effects , ▁cannot ▁be ▁subject ▁to ▁such ▁a ▁large ▁sex ▁difference ▁as ▁that ▁apparent ▁in ▁p let ys m ographic ▁studies . ▁These ▁ne uro log ists ▁c ite ▁the ▁existence ▁of ▁significant ▁volunte ering ▁bias ▁among ▁men ▁but ▁not ▁women ▁in ▁er ot ica ▁research , ▁in ▁particular ▁that ▁the ▁over re presentation ▁of ▁ere ct ile ▁d ys function ▁yet ▁under re presentation ▁of ▁sexual ity - related ▁shame ▁in ▁volunte ers ▁is