/usr/share/psychtoolbox-3/PsychAlphaBlending/ is in psychtoolbox-3-common 3.0.11.20140816.dfsg1-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/psychtoolbox-3/PsychAlphaBlending/AlphaBlend.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/AlphaDestinationTerm.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/AlphaSourceTerm.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/AlphaSum.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/AlphaTimes.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/Contents.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/GL_DST_ALPHA.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/GL_DST_COLOR.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/GL_ONE.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/GL_ONE_MINUS_DST_ALPHA.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/GL_ONE_MINUS_DST_COLOR.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/GL_ONE_MINUS_SRC_ALPHA.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/GL_ONE_MINUS_SRC_COLOR.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/GL_SRC_ALPHA.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/GL_SRC_ALPHA_SATURATE.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/GL_SRC_COLOR.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/GL_ZERO.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/MaskImageIn.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/MaskImageOut.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/SetDestinationAlpha.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/SetImageAlpha.m
/usr/share/psychtoolbox-3/PsychAlphaBlending/SetSourceAlpha.m