Fig. 1: Path integration task.

a Example path from top-down perspective. Participants began at the starting point (green dot) and then walked along the path (curved black line). There were four stopping points (red dots) along each path; at these points, participants were asked to report their estimate of the direct distance and angle to the path’s starting point. b During the experiment, participants saw a virtual environment from first-person perspective via a head-mounted display (HMD). Movements in the real world were tracked with a motion tracking system and translated to movements (i.e., changes in location and viewing orientation) in the virtual environment. Participants held a wooden stick and were guided by the experimenter along a path. At each stopping point, the direct distance to the starting point had to be estimated verbally in meters and centimeters, and participants turned their body on the spot to indicate the orientation to the starting point. c Three different virtual environments (left panel) used in the path integration task. Each environment comprised a ground plane and distant landmark cues. Landmark cues were rendered at infinity, in order to allow participants to determine their heading direction, but not position or distance information. One tile of each environment's ground plane is shown in the right panel. These tiles were textured to provide optic flow during movement, but were seamless (no visible border between adjacent tiles) and provided no fixed cues with positional information. d Overview of the 10 different paths used in the experiment. Each path contained three turns, and turn directions (i.e., left “L” and right “R” turns) were counter-balanced between paths. e Participants performed three blocks of the path integration task. Each block consisted of 16 paths (paths #1–10, and paths #1–6 repeated without intermediate stopping at stopping points 1–3). In addition, after the 4th and 12th path of each block, participants performed so-called “standardization-paths” (i.e., straight lines with a length of 2, 6, and 10 m), which were used to correct for each participant’s bias in converting their internal location estimate to a verbal response. Text in bold in panel e indicates the phases used for data analyses. See “Methods” section for more details.