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Gaulin (1992b) explains that to discuss this evolutionary theory, we must first recognize that spatial ability effects reproductive success. Currently, the ‘mating system hypothesis’ is the most widely-accepted explanation for these sex differences. Because the spatial organization of animal populations depends on the mating system of that species, differences in mating systems lead to differences in spatial learning. In monogamous species, pairs situate themselves apart from other pairs and both sexes experience similar environmental risks and rewards. In polygamous species, one sex orients itself apart from other same-sex individuals, similar to monogamous pairs, while the opposite sex travels from mate to mate. Therefore, in species where one sex has a much larger range to forage, hunt, or mate than the opposite sex, that sex should acquire some navigation advantage (Gaulin, 1992b).

In the rodent model, it is fairly clear that laboratory rats and polygynous species of wild rodents show a distinct male advantage on various types of maze tasks. This increased male spatial ability contrasts the absence of sex-differences in monogamous laboratory mice and monogamous wild rodent species (Puts, 2007).The hippocampus, a brain structure important for spatial processing, shows similar sex-differences that support this mating system hypothesis(see [link] ). The hippocampus of male and female monogamous rodent species are typically the same size while in polygynous species, males have been found to have a significantly lager hippocampi (Puts, 2007).

Conclusion

When looking at non-reproductive sex differences in any species, behavior is normally quantified as the frequency of the behavior or the level of performance and not the ways the actions are performed by different test groups or individuals. Trying to record differences in the physical actions performed would lead to subjective data collection based on the researcher’s observations and make it nearly impossible to standardize results between experimenters. It must also be noted that in learning experiments even a small amount of methodological variety can exaggerate or weaken the results. This makes reproduction of experiments difficult and weakens the validity of claims made in many of the articles I have discussed. Because of these methodological difficulties, there have been many debates over the legitimacy of rat-learning experiments and the learning processes involved.

Sex differences have been reported during acquisition, retention and loss of information in most of these paradigms. In general, female rats perform better than males in the classical eyeblink conditioning, in fear-potentiated startle and in most operant conditioning tasks, such as the active avoidance test. However, in the classical fear-conditioning paradigm, in certain lever-pressing paradigms and in conditioned taste aversion, males outperform females or are more resistant to memory extinction (Dalla, 2009). Although females expressed less learned helplessness, females may respond more negatively to stressful situations. A type of wall hugging behavior, called thigmotaxis , is often seen when an animal is introduced to a new (and potentially risky) environment. Perot-Sinal et. al ( 1996) showed that during water-maze tasks, female rats displayed more thigmotaxis, thus took longer to find the hidden platform (which is usually not near a wall) and performed less successfully. This sex difference was more pronounced at the beginning of training (Perrot-Sinal, 1996).

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Source:  OpenStax, Mockingbird tales: readings in animal behavior. OpenStax CNX. Jan 12, 2011 Download for free at http://cnx.org/content/col11211/1.5
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