Fig. 1: Generation of a ‘state-space’ to understand how the neural correlates of personality traits are differentially expressed across task situations.

To simultaneously map neural activity across individuals and situations we utilised a state-space approach^19,20,21 in which we calculated the correlation between the whole brain map of an individual’s brain activity in a specific task condition (contrasted with the respective baseline) with each of the three dimensions of brain variation generated by the decomposition of brain activity at rest¹⁴. This results in a series of values which can be considered to be co-ordinates in a 3-dimensional space upon which we can conduct inferential statistics to understand how neural activity changes across situations and individuals and how these two influences on brain activity interact. (See Supplementary Fig. 1 for the distribution of all individuals’ maps within the space and Supplementary Fig. 2 for the group average of each task condition within the state space). The location on a dimension in this analysis describes the degree of fit between an observed brain map and the relative levels of activity described by the specific gradient. Thus, if one map is higher on gradient 3 than another map, the first map would have higher activity in the fronto-parietal system than in the DMN, compared to the second map.