Fig. 1.

The endpoint weightings format of line bisection. (a) The stimulus sheet with a single line is placed directly in front of the patient, who is asked to bisect the line by marking a position (P). In the traditional task analysis, the line in this example would be considered as 120 mm long, displaced 20 mm towards the right hemispace, and the patient's response would be scored as a +10 mm deviation from the true midpoint of the line. In the endpoint weightings analysis, the positions of the response (P) and of the left (L) and right (R) endpoints are coded as horizontal coordinates relative to a fixed environmental reference, in this case the centre of the page (0). The patient in this example has responded at +30 mm, with L at −40 mm and R at +80 mm. (b) In a basic version of the endpoints line bisection task, a set of stimulus lines (A-D) is generated by crossing two positions of L (−40, −80) with two positions of R (+40, +80). Each line is presented individually, with eight repetitions for each stimulus line. The analysis focuses on how P varies as a consequence of changes in L (lines A&C vs B&D) or changes in R (lines A&B vs C&D). See Methods for full details.