Within the Extreme Male Brain theory, Autism Spectrum Disorder is characterised as a deficit in empathising in conjunction with preserved or enhanced systemising. A male advantage in systemising is argued to underpin the traditional male advantage in mental rotation tasks. Mental rotation tasks can be separated into rotational and non-rotational components, and circulating testosterone has been found to consistently relate to the latter component. Systemising was found to correlate with mental rotation, specifically the non-rotational component(s) of the mental rotation task but not the rotational component of the task. Systemising also correlated with a proxy for circulating testosterone but not a proxy for prenatal testosterone. A sex difference was identified in systemising and the non-rotational aspect of the mental rotation task.