Nineteen males and nineteen females were tested. Each was given 5 practice trials at the start using the Ego-1 condition with no masking area and a 4 cm/sec ball speed. This provided the opportunity to see the ball cross the intersect line, as well as practice in moving the paddle to the intersect point. Experiment 2. Color Shade Discrimination The ability to discriminate a brief color change in a white ball was measured in 15 females and 13 males. Participants were given 5 practice trials at the 4 cm/sec ball speed using the Ego-1 condition to familiarize them with the testing conditions. The Ego- 2 and Allo-1 conditions were for testing. The order of presentation for all subjects was Ego-2 (4 cm/sec), Allo-1 (4 cm/sec), Ego-2 (8 cm/sec), Allo-1 (8 cm/sec). Ten trials were presented for each condition at each speed. The white ball always changed color for 100 milliseconds, just prior to passing beneath the masking screen, which was 4 cm below the intersect line. The color boxes appeared 2000 milliseconds after the ball passed through the intersect line. Color accuracy and reaction time were measured on each trial. Experiment 3. Effect of Dual attention and Ball Speed on Target and Color Accuracy We tested 19 males and 27 females in the color/target dual attention task that primed participants for both object and movement processing at the start of each trial. Participants were given 5 practice trials at the 4 cm/sec ball speed using the Ego-1 condition to familiarize them with the testing conditions. For the experiment that followed, 20 random trials were presented under each ball orientation and speed, with the set split equally between color and targeting. The masking screen was 4 cm below the intersect line, and the paddle or the color boxes appeared 2000 milliseconds after the ball passed through the intersect line. The order of presentation for all subjects was Ego-2 4 cm/sec, Allo-2, 4 cm/sec, Ego-2 8 cm/sec, and Allo-2 8 cm/sec. Reaction time was measured for both target and color responses. References 1. Maccoby EE, Jacklin CN (1974) The Psychology of Sex Differences, Vol. 1. Stanford Univ. Press, Stanford, CA. 2. Handa RJ, McGivern RF (2002) Androgen receptors in the brain: A behavioral perspective. In: Androgens and Androgen Receptor: Mechanisms, Functions and Clinical Applications Chang CC, ed. Kluwer Academic/Plenum Publishers, New York, NY. 3. Ungerleider LG, Mishkin M (1982) Two Cortical Visual Systems. In: Analysis of Visual Behavior (Ingle DJ, et al., Eds), MIT Press, Cambridge, MA. pp 549–586. 4. Goodale MA, Milner AD (1992) Separate visual pathways for perception and action. Trends in Neuroscience 15: 20–25. 5. Kravitz DJ, Saleem KS, Baker CI, Mishkin M (2011) A new neural framework for visuospatial processing. Nat Rev Neurosci 12: 217–330. 6. Ellis L, Hershberger S, Field E, Wersinger S, Pellis S, et al. (2008) Sex Differences: Summarizing More Than a Century of Research. Psychology Press, Taylor & Francis, Oxford. 7. Beatty WW (1984) Hormonal organization of sex differences in play fighting and spatial behavior. Prog Br Res 61: 315–330. 8. McGivern RF, Clancy AN, Hill MA, Noble EP (1984) Prenatal alcohol exposure alters adult expression of sexually dimorphic behavior in the rat. Science 224: 896–898. 9. Mueller SC, Jackson CP, Skelton RW (2008) Sex differences in a virtual water maze: an eye tracking and pupillometry study. Behav Brain Res 193: 209–215. 10. Perrot-Sinal TS, Kostenuik MA, Ossenkopp KP, Kavaliers M (1996) Sex differences in performance in the Morris water maze and the effects of initial nonstationary hidden platform training. Behav Neurosci 110: 1309–1320. 11. Cleveland A, Rocca AR, Wendt EL, Westergaard GC (2003) Throwing behavior and mass distribution of stone selection in tufted capuchin monkeys (Cebus apella). Am J Primatol 61: 159–172. 12. Watson NV, Kimura D (1991) Nontrivial differences in throwing and intercepting: Relation to psychometrically defined spatial functions. Pers Individ Diff 12: 375–385. Sex Differences in Processing Movement vs Objects Experiment 4. Within-Subject Comparison of Target and Color Accuracy Tested Alone and Under Dual Attention Conditions This experiment examined whether the results of Experiment 3 were related to a lack of experience with the targeting and color recognition tasks. We conducted a within-subject comparison where 17 females and 15 males were tested first in the color alone and the target alone conditions, and finally in the color/target dual attention task. The order of presentation for the color alone and target alone was counterbalanced within sex, and the dual attention was always the last task presented. We used the Allo-1 perspective at a ball speed of 5.0 cm/sec. Ten trials each were presented for the color alone and target alone conditions. For the dual attention task, 20 trials were presented, which were split randomly between color shade recognition and targeting. The masking screen was 4 cm below the intersect line, and the paddle or the color boxes appeared 2000 milliseconds after the ball passed through the intersect line. All participants were given 5 practice trials on the color alone and the target alone conditions at the 3.5 cm/sec ball speed using the Ego-1 condition immediately before testing. Acknowledgments We thank Gabriel Delgadillo, Matthew Gonzer, Ken Gorciak, Amanda Khan, Alice Lu, Janelle Pineda, Abdullah Shehadeh, Christopher West, and Jackie Yip for their help with the data collection and analysis. We also thank Kandis L. Mutter for insightful comments on the perceptual nature of spatial and verbal tasks that helped in the development of these studies. Author Contributions Conceived and designed the experiments: RFM RJH JAP. Performed the experiments: BA. Analyzed the data: RFM BA. Contributed reagents/ materials/analysis tools: RFM. Wrote the paper: RFM JAP. 13. Andreano JM, Cahill L (2009) Sex influences on the neurobiology of learning and memory. Learn Mem 16: 248–266. 14. Kimura D (1999) Sex and Cognition. MIT Press, Cambridge, MA. 15. Kansaku K, Kitazawa S (2002) Imaging studies on sex differences in the lateralization of language. Neurosci Res 41: 333–337. 16. Ragland JD, Coleman AR, Gur RC, Glahn DC, Gur RE (2000) Sex differences in brain-behavior relationships between verbal episodic memory and resting regional cerebral blood flow. Neuropsychologia 38: 451–461. 17. Voyer D, Postma A, Brake B, Imperato-McGinley J (2007) Gender differences in object location memory: a meta-analysis. Psychon Bull Rev 14: 23–38. 18. Silverman I, Eals M (1992) Sex differences in spatial abilities: Evolutionary theory and data. In JH. Barkow, L. Cosmides, J. Tooby, eds. The adapted mind: Evolutionary psychology and the generation of culture. Oxford University Press, New York. pp 533–549. 19. McGivern RF, Mutter KL, Anderson J, Wideman G, Bodnar M, et al. (1998) Gender differences in incidental learning and visual recognition memory: support for a sex difference in environmental awareness. Pers Ind Diff 25: 223–232. 20. Alexander GM, Packard MG, Peterson BS (2002) Sex and spatial position effects on object location memory following intentional learning of object identities. Neuropsychologia 40: 1516–1522. 21. Choi J, L’Hirondelle N (2005) Object location memory: A direct test of the verbal memory hypothesis. Learn Ind Diff 15: 237–245. 22. Lejbak L, Vrbancic M, Crossley M (2009) The female advantage in object location memory is robust to verbalizability and mode of presentation of test stimuli. Br Cogn 67: 148–153. 23. McGivern RF, Huston JP, Byrd D, King T, Siegle G, et al. (1997) Sex differences in recognition memory in children before and after puberty. Br Cogn 34: 323–336. 24. Lewin C, Wolgers G, Herlitz A (2001) Sex differences favoring women in verbal but not in visuospatial episodic memory. Neuropsychology 15: 165–173. 25. James TW, Kimura D (1997) Sex differences in remembering the locations of objects in an array: Location-shifts versus location-exchanges, Evolution and Human Behavior 18: 155–163. PLoS ONE | www.plosone.org 11 March 2012 | Volume 7 | Issue 3 | e32238