The parallel map theory provides a theoretical framework for sex differences in cognition and brain structure in vertebrates. We’ve recently published four journal articles in this area, ranging from maze and object learning in mice (Bettis & Jacobs, 2013; 2012), to the development of spatial memory in children (Waismeyer & Jacobs, 2013) and virtual navigation in adult humans (Chai & Jacobs, 2012). Across these studies, we show that males (both mice and men) preferentially rely on “directional cues”, the extended stimuli encoded by the bearing map such as the geometry of a landmark array or a distant beacon, while females preferentially use “positional cues”, the discrete objects such as small landmarks encoded by the sketch map. Anna Waismeyer (née Waisman), currently a postdoc at the University of Washington, Seattle, has extended her dissertation work on spatial coding in the fox squirrel to child development. In our 2013 manuscript, we show that directional cues were used more heavily by boys and that this sex difference emerged at 4 years of age. This agrees with the PMT interpretation about the ontogeny of the bearing and sketch maps (‘ontogeny recapitulating phylogeny’, at least in this case) and the heavier weighting of the bearing map in males compared to females. A second developmental effect, predicted by PMT, was our study that the masculinization of the digit ratio in women – the relative length of the index and ring fingers on the dominant hand, a proposed bioassay for fetal exposure to androgens – is positively correlated with a bearing map competency (initial heading direction from start point) in a virtual environment (Chai & Jacobs, 2012).