20-24 a adult adults anxiety appearance baden-württemberg blonde boredom breisgau by caucasian chair classroom close-up closed colour contemplation day depression-sadness despair differential disappointment displeased distraught education emotional exhaustion eyes focus freiburg front frustration german germany hair hall hand hands hat head headshot horizontal im image in indoors learning lecture lifestyles loneliness males man men mouth one only over people person photography problems repetition row sadness seat shirt side sitting solitude stress student tired university view wood-material worried years young