1. Left-handed athletes have been shown to have an advantage in interactive sports such as tennis, with left-handers making up a disproportionately high percentage of top players. 2. One theory for this advantage is the "negative perceptual frequency effects" hypothesis, which suggests that right-handed athletes are less practiced at perceiving and predicting movements from left-handed opponents. 3. A study tested this by having right and left-handed participants with different levels of tennis experience try to predict the direction and depth of tennis shots from video clips of both right and left-handed players. It found support for the idea that the ability to perceive left-handed movements is less developed.

1. The advantage of being left-handed In interactive sports Norbert,H. (2009)Attention, Perception, & Psycholophysics, 71(7), 1641-1648.

2. 證明左撇子在互動式運動具有優勢是因negative perceptual frequencyeffects。

3. 左撇子比例約為10%-13%，卻在互動式運動表現突出，(boxing,)以網球為例。 TOP10 比例 male, 24.06%; female, 11.80%。 大滿貫決賽 male, 22.27%; female, 18.75%。

4. 解釋左撇子優勢的理論 Earlier Explanations: 1.Innate superiority hypothesis. (Geschwind and Gal- aburda 1987) 2.Strategic advantage hypothesis. (Grouios, 2004; Grouios, Koidou, Tsorbatzouidis, & Alexandris, 2002)

5. Perception of Human Movements: 1.Focus of orientation in the perception of humanmovements. ( Pollick, Lestou, Ryu, & Cho, 2002) 2. Side-specific perception of human movements in sport. ( McMorris and Colenso 1996)

6. Earlier Explanations: 1.Innate superiority hypothesis. (Geschwind and Gal- aburda 1987) 2.Strategic advantage hypothesis. (Grouios, 2004; Grouios, Koidou, Tsorbatzouidis, & Alexandris, 2002)

7. Earlier Explanations: 1.Innate superiority hypothesis: Left-handerspossess a neuropsychological advantage. 2.Strategic advantage hypothesis. They have a strategic or tactical advantage .

8. Perception of Human Movements: 1.Focus of orientation in the perception of humanmovements. ( Pollick, Lestou, Ryu, & Cho, 2002) 2. Side-specific perception of human movements in sport. ( McMorris and Colenso 1996)

9. Perception of Human Movements 1.Focus of orientation in the perception of humanmovements. -These studies assume that this sensitivity in distinguishing between different human movements depends on visual experience.

10. Perception of Human Movements 2. Side-specific perception of human movements in sport. - This strong dependence on both visual experience and the horizontal orientation, it is proposed the sport-type-specific ability with the left hand is less well developed.

11. Perception of Human Movements Negative perceptual frequencyeffects hypothesis. -The lower frequency with which athletes in interactive sports are confronted with movements by left-handed opponents.

12. Method Participants: -108 males, 54 right-handers (RH) and 54 left-handers selected with the German version of the EHI . -Divided into three groups by experience. (experts,intermediates,novices)

13. Method Test Procedure -The participants viewed videotaped sequences of tennis strokes on a laptop computer and had to predict the direction and depth of each stroke.

14. videotaped sequences Two left-handed and two right-handed. Twelve strokes (six groundstrokes, four volleys, and two serves) were recorded from each player.加上鏡射呈現 Total 96video clips.受試者對於球的落點做預測，再以radial error 計算誤差。

15. federer.vs.nadal.wimbledon.2006. federer.vs.nadal.wimbledon.2007. federer.vs.roddick.wimbledon.2009.

17. Method 3 (group) × 2 (handedness of participant) × 2 (playing hand in video) × 2 (initial handedness of player in video) mixed ANOVA.

18. Results

19. Results

20. Results

21. Discussion The ability to discriminate left-handed movement patterns is less well developed than that for right-handed movement patterns.

22. Discussion Does the Participants’ own Handedness exert an Influence?

23. 以Mirror neurons來看: A left-hander might be easier for a left-hander to discriminate than for a right-hander. 結果並非如此

24. Discussion Do the Movement Patterns of left-Handers Simply Mirror the Movements of Right-Handers? There should also be no interaction between the playing hand in video and initial handedness of player in video variables.

25. Discussion Negative perceptual frequency effect (see Faurie & Ray-mond, 2005) and can be assigned to the set of strategic advantages of left-handers in sport.

26. Discussion Automated decision preferences that are generalized incorrectly from tactical play against right-handers.