/usr/share/psychtoolbox-3/PsychHardware/LinuxX11ExampleXorgConfs/ is in psychtoolbox-3-common 3.0.12.20160126.dfsg1-1ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/psychtoolbox-3/PsychHardware/LinuxX11ExampleXorgConfs/Contents.m
/usr/share/psychtoolbox-3/PsychHardware/LinuxX11ExampleXorgConfs/xorg.conf_DualXScreen_TripleHead_Nouveau
/usr/share/psychtoolbox-3/PsychHardware/LinuxX11ExampleXorgConfs/xorg.conf_FourSeparateScreens_nouveau
/usr/share/psychtoolbox-3/PsychHardware/LinuxX11ExampleXorgConfs/xorg.conf_SeparateScreensDualFireGL
/usr/share/psychtoolbox-3/PsychHardware/LinuxX11ExampleXorgConfs/xorg.conf_SeparateScreensIntel
/usr/share/psychtoolbox-3/PsychHardware/LinuxX11ExampleXorgConfs/xorg.conf_SeparateScreensNouveau
/usr/share/psychtoolbox-3/PsychHardware/LinuxX11ExampleXorgConfs/xorg.conf_SeparateScreensR600
/usr/share/psychtoolbox-3/PsychHardware/LinuxX11ExampleXorgConfs/xorg.conf_ThreeSeparateScreens1+1+2_nouveau
/usr/share/psychtoolbox-3/PsychHardware/LinuxX11ExampleXorgConfs/xorg.conf_ThreeSeparateScreens_nouveau
/usr/share/psychtoolbox-3/PsychHardware/LinuxX11ExampleXorgConfs/xorg.conf_TwoScreens_DP1+DVI_HD5770
/usr/share/psychtoolbox-3/PsychHardware/LinuxX11ExampleXorgConfs/xorg.conf_TwoSeparateScreens2+2_nouveau
/usr/share/psychtoolbox-3/PsychHardware/LinuxX11ExampleXorgConfs/xorg.conf_intel