Biological Motion Perception

1. Biological Motion Perception • Lavanya Sharan • March 28th, 2011

2. Studying human movements Etienne-Jules Marey (1884) developed ‘chronophotography’ Image sources: Wikimedia Commons, science-television.com Slide content: Blake & Shiffrar (2007)

3. Point Light Walker is born Markers attached to head and joints. Videos of walking, running etc. Can use animation and motion captures techniques for the same purpose. Point light (PL) animations are now the mainstay of biological motion research. Image source: Johansson (1973) Slide content: Blake & Shiffrar (2007)

4. Examples of PL motions Phase-scrambled motion Normal motion Video source: Randolf Blake Lab Slide content: Blake & Shiffrar (2007)

5. Alternative to PL animations Knoblich & Flach (2001) Hodgins et al. (1998) McDonnell et al. (2009) Very few studies that use ‘embodied’ forms. Slide content: Blake & Shiffrar (2007)

6. What have we learn from PLWs? Human motion perception is quite robust. Video source: Randolf Blake Lab Slide content: Blake & Shiffrar (2007)

7. What have we learn from PLWs? Human motion perception is quite robust. Brief exposures (<100 ms) Johannson 1973 Blurry dots, randomized contrast polarity over time Mather et al., 1992, Ahlstrom et al. 1997 Stereoscopic depths are scrambled Ahlstrom et al. 1997, Bulthoff et al. 1998, Lu et al. 2006 Dynamic noise dots Bertenthal & Pinto 1994, Cutting et al. 1998, Ikeda et al. 2005 Markers not on joints Bertenthal & Pinto 1994 Slide content: Blake & Shiffrar (2007)

8. What have we learn from PLWs? How much can we tell about a figure? Identity of figure Cutting & Kozlowski 1977, Fani et al. 2005, Troje et al. 2005 Sex of figure Kozlowski & Cutting 1977, 1978, Mather & Murdoch 1994, Sumi 2000, Troje 2002, Pollick et al. 2005 Activities of two or more individuals Mass et al. 1971 Emotional content Clarke et al. 2005, Dittrich et al. 1996, Walk & Homan 1984 Facial expressions Bassili 1978, Hill et al. 2003 Interactions with objects Bingham 1993, Stoffregen & Flynn 1994 Slide content: Blake & Shiffrar (2007)

9. What have we learn from PLWs? Inversion effects for body motions (Sumi 1984) Video source: Randolf Blake Lab Slide content: Blake & Shiffrar (2007)

10. What have we learn from PLWs? Sensitive to certain factors. Number of markers and exposure duration Neri et al. 1998, Poom & Olsson 2002, Thornton et al. 1998 Impaired recognition in periphery Ikeda et al. 2005 Dim lighting Grossman & Blake 1999 Phase scrambling Grossman & Blake 1999, Hiris et al. 2005 Temporal duration Beintema et al. 2003 Relative position of markers (form) Beintema & Lappe 2002, Beintema et al. 2006, Hiris et al. 2005 Slide content: Blake & Shiffrar (2007)

11. What have we learn from PLWs? Not limited to humans. Video source: Randolf Blake Lab Slide content: Blake & Shiffrar (2007)

12. What have we learn from PLWs? Biological recognition develops early. 4 and 8 month olds respond to human motion vs. scrambled dots. Bertenthal 1993, Fox & McDaniel 1982, Hirai & Hiraki 2005, Reid et al. 2006 Reach adult level performance by age 5 Pavlova et al. 2001 Older adults can perceive human motion inspite of age-related deficits in visual processing Norman et al. 2004 Slide content: Blake & Shiffrar (2007)

13. Binocular rivalry Perceived background flow Top-down vs. bottom-up? Inversion effects Good performance at temporal display rates higher than needed for low-level processing Requires focused visual attention Low-level models of motion processing Longer ISIs impair performance Image source: cs.bham.ac.uk Slide content: Blake & Shiffrar (2007)

14. Motoric contributions to human motion perception Action recognition and action planning share representations Prinz 1997, Hommel et al. 2001 Carrying out the same action as the PL figure improves performance Reed & Farah 1995, Jacobs & Shiffrar 2005, Hamilton et al. 2004 Better at recognizing one’s own actions Knoblich & Flach 2001, Loula et al. 2005, Jacobs et al. 2004 Individual with motor deficit perform differently on motion perception tasks Bosbach et al. 2005, Funk et al. 2005, Shiffrar 2006, Pavlova et al. 2003 Chameleon effect Chartrand & Bargh 1999 Slide content: Blake & Shiffrar (2007)

15. Social cues & human motion perception Can tell a lot about identity, sex, sexual orientation, dancing ability etc. Loula et al. 2005, Barclay et al. 1978, Brownlow et al. 1997, Montepare & Zebrowitz-McArthur 1988, Gunns et al. 2002, Runeson & Frykholm 1983 Can identify emotion from PL figures Atkinson et al. 2004, Pollick et al. 2001 Angry walker easier to detect than other emotions Chouchourelou et al. 2006 Chameleon effect or social mimicry important for social interactions Chartrand & Bargh 1999 Slide content: Blake & Shiffrar (2007)

16. Neural basis of human motion perception Neurons in macaque STS Perrett et al. 1982, 1985, Oram & Perrett 1996, Shiffrar 1994 Mirror neurons Rizzolatti et al. 2001, Rizzolatti & Craighero 2004 Many case studies of individuals with deficits including autism Schenk & Zihl 1997, Vaina et al. 1990, Cowey & Vaina 2000, Battelli et al. 2003, Jokisch et al. 2005, Blake et al. 2003, Kim et al. 2005, Virji-Babul et al. 2003, Pavolova et al. 2006 TMS studies in STS Grossman et al. 2005 Unlike MT, STSp selective for biological motion Grossman et al. 2000, Grossman & Blake 2001, Grossman et al. 2004 Image source & slide content: Blake & Shiffrar (2007)

17. Superior temporal sulcus (STSp) More activation in right hemisphere Beauchamp et al. 2003, Grossman et al. 2000, Peusken et al. 2005, Santi et al. 2003 Crude retinotopy Grossman et al. 2000 Whole body motion, motion of body parts Pelphrey et al. 2003, Calvert et al. 1997, Grezes et al. 1998, Puce et al. 1998 Statics figures do not produce activation Pelphrey et al. 2003, Peuskens et al. 2005 Sounds of footsteps Bidet-Caulet et al. 2005 Intentionality of actions and social judgments Saxe et al. 2004, Frith & Frith 1999, Morris et al. 2005, Winston et al. 2002, Allison et al. 2000, Iacoboni et al. 2004 Image source & slide content: Blake & Shiffrar (2007)

18. Open questions McDonnell et al. (2009) Connection between faces & bodies? Interactions with motor and social learning? What about more real-world stimuli? Slide content: Blake & Shiffrar (2007)