## 3 Results
### Coupling between Lateral Bending and Rotation during Heading and Pointing
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & & & & \multicolumn{3}{c}{HEADING} & & \\  & & E & NE & N & NW & W & SW & S & SE \\ \hline \multirow{3}{*}{AP} & head & \(-2.8\pm 0.8\) & \(7.3\pm 1.0\) & \(15.1\pm 1.3\) & \(8.0\pm 0.9\) & \(-1.6\pm 0.7\) & \(-9.9\pm 1.0\) & \(-13.2\pm 1.4\) & \(-9.4\pm 0.9\) \\  & trunk & \(-1.5\pm 1.6\) & \(-2.4\pm 1.6\) & \(-1.5\pm 1.4\) & \(-1.5\pm 1.5\) & \(-1.7\pm 1.6\) & \(-1.2\pm 1.6\) & \(-0.9\pm 1.6\) & \(-0.9\pm 1.5\) \\  & H vs. T & \(-0.7\pm 1.6\) & \(10.2\pm 1.4\) & \(16.6\pm 1.3\) & \(9.0\pm 1.2\) & \(-0.4\pm 1.6\) & \(-8.8\pm 2.3\) & \(-12.2\pm 2.4\) & \(-8.2\pm 2.2\) \\ \hline \multirow{3}{*}{LA} & head & \(7.7\pm 0.8\) & \(7.1\pm 1.1\) & \(0.8\pm 0.6\) & \(-5.8\pm 0.7\) & \(-7.4\pm 0.6\) & \(-2.6\pm 0.7\) & \(0.1\pm 0.4\) & \(2.6\pm 0.6\) \\  & trunk & \(-0.5\pm 0.7\) & \(-0.9\pm 0.7\) & \(-0.6\pm 0.7\) & \(-0.9\pm 0.7\) & \(-1.0\pm 0.8\) & \(-1.4\pm 0.7\) & \(-0.9\pm 0.7\) & \(-0.9\pm 0.7\) \\  & H vs. T & \(6.0\pm 1.0\) & \(4.8\pm 1.1\) & \(-1.6\pm 0.7\) & \(-7.5\pm 1.0\) & \(-8.3\pm 0.9\) & \(-2.7\pm 1.0\) & \(-0.2\pm 0.7\) & \(1.7\pm 0.8\) \\ \hline \multirow{3}{*}{RO} & head & \(-17.0\pm 1.2\) & \(-9.3\pm 1.1\) & \(-0.7\pm 0.4\) & \(8.5\pm 0.6\) & \(16.0\pm 1.3\) & \(10.6\pm 1.0\) & \(-0.4\pm 0.5\) & \(-14.3\pm 1.1\) \\  & trunk & \(-5.2\pm 1.1\) & \(-5.2\pm 1.2\) & \(-4.3\pm 1.5\) & \(-4.2\pm 1.4\) & \(-3.8\pm 1.7\) & \(-4.1\pm 1.6\) & \(-4.5\pm 1.4\) & \(-5.0\pm 1.3\) \\  & H vs. T & \(-12.0\pm 1.9\) & \(-4.6\pm 1.8\) & \(2.8\pm 1.3\) & \(12.5\pm 1.4\) & \(19.7\pm 1.4\) & \(14.9\pm 1.4\) & \(4.1\pm 1.2\) & \(-9.3\pm 1.7\) \\ \hline \multicolumn{7}{c}{POINTING} & & & \\  & E & NE & N & NW & W & SW & S & SE \\ \hline \multirow{3}{*}{AP} & head & \(-3.3\pm 1.5\) & \(1.7\pm 2.9\) & \(4.8\pm 1.7\) & \(1.8\pm 1.2\) & \(-3.8\pm 1.0\) & \(-8.3\pm 1.4\) & \(-8.1\pm 1.6\) & \(-6.8\pm 1.8\) \\  & trunk & \(2.2\pm 1.6\) & \(2.2\pm 1.6\) & \(2.5\pm 1.7\) & \(3.3\pm 2.0\) & \(2.4\pm 1.9\) & \(2.0\pm 1.8\) & \(1.9\pm 1.6\) & \(2.2\pm 1.5\) \\  & H vs. T & \(-5.7\pm 1.9\) & \(-0.4\pm 3.0\) & \(2.1\pm 1.6\) & \(3.2\pm 5.2\) & \(-5.2\pm 2.0\) & \(-9.8\pm 2.3\) & \(-9.7\pm 2.3\) & \(-9.1\pm 2.7\) \\ \hline \multirow{3}{*}{LA} & head & \(2.6\pm 0.9\) & \(0.5\pm 1.4\) & \(-0.9\pm 0.5\) & \(-5.6\pm 1.0\) & \(-6.9\pm 1.1\) & \(-4.2\pm 1.0\) & \(-1.3\pm 1.0\) & \(0.0\pm 1.0\) \\  & trunk & \(0.6\pm 1.1\) & \(0.4\pm 1.1\) & \(1.4\pm 1.1\) & \(0.3\pm 1.3\) & \(-0.4\pm 1.2\) & \(-0.7\pm 0.9\) & \(-0.1\pm 1.0\) & \(0.6\pm 0.8\) \\  & H vs. T & \(2.1\pm 1.5\) & \(0.3\pm 1.6\) & \(-0.2\pm 1.8\) & \(-3.1\pm 1.8\) & \(-3.2\pm 1.8\) & \(-1.7\pm 1.3\) & \(-0.6\pm 1.1\) & \(-0.4\pm 1.1\) \\ \hline \multirow{3}{*}{RO} & head & \(-12.0\pm 3.1\) & \(-8.7\pm 2.1\) & \(-1.9\pm 0.7\) & \(3.5\pm 1.3\) & \(7.3\pm 2.0\) & \(4.4\pm 1.5\) & \(-1.9\pm 1.7\) & \(-7.6\pm 3.4\) \\  & trunk & \(-0.9\pm 1.8\) & \(-0.8\pm 1.9\) & \(3.4\pm 2.9\) & \(6.9\pm 3.4\) & \(9.4\pm 4.7\) & \(6.4\pm 3.2\) & \(2.0\pm 2.2\) & \(-0.8\pm 1.7\) \\ \cline{1-1}  & H vs. T & \(-11.3\pm 3.7\) & \(-8.1\pm 3.0\) & \(-5.4\pm 2.8\) & \(-2.9\pm 2.2\) & \(-1.3\pm 3.0\) & \(-0.9\pm 2.3\) & \(-3.3\pm 2.9\) & \(-7.8\pm 3.6\) \\ \hline \end{tabular}
\end{table} 
Table 1: Mean values for 10 participants of Euler angles (expressed in degrees) representing the orientation of the head and trunk in space and the head by reference to the trunk (H vs. T) for the different target directions. AP: Anteriorosterior tilt, LA lateral tilt, RO: axial rotation. Target directions: E: East, NE: Northeast, N: North, NW: Northwest, W: West, SW: Southwest, S: South, SE: Southeast. Data are mean \(\pm\) SEM. Figure 3: Variation of the head orientation by reference to the trunk as a function of target direction. The graphs represent the Euler angles (anterior/posterior tilt, lateral tilt and axial rotation) describing the orientation of the head relative to the trunk at the time of heading (blue circles) and pointing (pink circles). Each point represents the mean \(\pm\) SEM of 10 participants.