No / Significant changes in endogenous plasma hormone levels are required to sustain pregnancy which provides a unique opportunity to study their effect on cognitive function. Four carefully selected tests from the Cambridge Neuropsychological Automated Test Battery (CANTAB) were administered to assess the cognitive function of a group of 23 women during each trimester of pregnancy and at three months following birth. Test scores were compared with a control group of 24 non-pregnant women. The Edinburgh Postnatal Depression Scale was administered to assess anxiety and risk of depression. The National Adult Reading Test (NART) was used as a measure of verbal intelligence. Plasma hormone levels were measured at each time-point. The pregnant group scored significantly lower than the control group on the Spatial Recognition Memory (SRM) test at the second trimester and postpartum assessments (p ⩽ 0.004). A significant pregnant group-time interaction (p = 0.005) for SRM performance was demonstrated. Compared to their first trimester assessment, the pregnant group scored on average 11.7% less on each subsequent SRM test. The pregnant group reported more symptoms of anxiety and depression compared to the control group (EPDS-4 point increase in mean score at each assessment, p = 0.002). There were no plasma hormone levels and test score associations identified.

Kin recognition is the ability to identify a conspecific as a relative and can occur even when animals are complete strangers. By being able to recognise relatives, animals are able to give preferential treatment to those with which they share genes. Recognition may occur by either direct familiarisation (learning a phenotypic cue that reliably correlates to kinship), or by indirect familiarisation (learning kinship relationships through previous encounters). Rats (Rattus norvegicus) can recognise kin, however to what degree kin recognition is mediated by genetics (direct familiarisation) or social relationships (indirect familiarisation) are unknown; the influences of kinship and familiarity on the ability to learn from a conspecific is also unknown. Furthermore, the sex of an animal can also influence its ability to learn but this effect has received little attention in the literature, particularly when considering observational learning tasks. I assessed if relatedness and/or familiarity influenced a rat's ability to learn through observation, and if gender relationships influence the learning process. Eighty rats ( observers ) were given the opportunity to observe a demonstrator rat press a joystick in a given direction to obtain a food reward. Observers watched a demonstrator that had one of the following relationships with them: related and familiar, related and unfamiliar, unrelated and familiar, or unrelated and unfamiliar. When observers were given the opportunity to manipulate the joystick, the number of sniffs of the joystick, the latency to first move the joystick and the total number of presses were recorded. Rats that were both familiar and related to the demonstrator consistently performed better than any other treatment group; furthermore, rats that were familiar with the demonstrator performed the task more efficiently than rats that were not familiar with the demonstrator. When the demonstrators and observers were related, the observers produced more presses and sniffs of the joystick while having a lower latency to the first push In addition, male observers learnt better than females regardless of the demonstrator sex, with males that were familiar to their demonstrator making nearly twice as many pushes than any other treatment group. The results from this study are discussed in relation to both the mechanisms of direct and indirect recognition and the potential adaptive value on kin discrimination in the learning process. The home range hypothesis may explain why gender differences in learning were found: male rats have larger home ranges than females. Male rat will regularly encounter more rats than females and would need to ascertain if unfamiliar individuals are relatives. Females remain closer to natal sites and as such are more likely to encounter kin and therefore may not need as well as developed kin recognition ability.