This analysis was carried out to detect any significant differences in
the spatial distribution of SPSs between the good and poor heartbeat
perceivers. Shaded areas on each printed hand were projected onto a
140 mm × 140 mm grid with 1 mm2 resolution and then converted
into binary codes (0 = not shaded cell; 1 = shaded cell). The result,
for each hand of each participant,was an individual map of spatially distributed
binary codes representing the shaded areas. A frequency map
was obtained by superimposing the individual binary maps, with the
value in each cell representing the percentage of participants who had
shaded it in (flanker hands in Fig. 1).