Psychoneuroendocrinology 24 (1999) 175 – 192 Sex differences and menstrual cycle effects in human spatial memory Albert Postma *, Joke Winkel, Adriaan Tuiten, Jack van Honk Psychological Laboratory, Department of Psychonomics, Utrecht Uniersity, Heidelberglaan 2, 3584 CS Utrecht, The Netherlands Received 23 June 1998; accepted 11 September 1998 Abstract A typical test of spatial memory requires subjects to relocate a number of objects in their original, previously studied positions. It has been argued that this test includes multiple separate processing components (Postma, A., De Haan, E.H.F., 1996. Quarterly Journal of Experimental Psychology 48A (1), 178 – 199; Postma, A., Izendoorn, R., De Haan, E.H.F., 1998. Brain and Cognition 36, 334 – 345). One has to encode the precise positions occupied, assign the various objects to the correct (relative) locations, and achieve an integration of both types of spatial information. The present study examined the presence of sex differences and the role of hormonal factors for these selective components of spatial memory. A computerised, immediate (working) memory version of the test was used, comparing 23 males and 34 females on three experimental conditions: positions only, object-to-position-as- signment, and the combined condition, requiring integration of the other two components. In line with previous research (Postma et al., 1998) males showed a selective advantage for fine-grained, metric positional reconstruction (i.e. positions-only). Interestingly, a within-sub- jects comparison in the females only revealed a menstrual cycle effect for exactly the same dimension of spatial memory. In the nonmenstrual phase, females were better than during menstruation. This clearly implies a role for sex hormones in spatial memory, even though a subsequent analysis of testosterone samples in saliva did not reveal a significant correlation with measures of spatial memory in both males and females. © 1999 Elsevier Science Ltd. All rights reserved. Keywords: Spatial memory; Sex differences; Menstrual cycle; Testosterone * Corresponding author. Tel.: +31-30-2533657/2534281; e-mail: a.postma@fss.uu.nl. 0306-4530/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved. PII:S0306-4530(98)00073-0