Does stress influence the performance of cardiopulmonary resuscitation? A narrative review of the literature.

Cardiopulmonary resuscitation represents a major physical and psychological challenge for all involved health care workers because survival of the patients is closely related to the timely and accurate actions of rescuers. Consequently, rescuers may experience high levels of acute mental stress. Stress, in turn, may influence attentional resources and distractibility, which may affect the quality of resuscitation. This narrative review summarizes the current state of research concerning the influence of stress on resuscitation performance. Peer-reviewed studies retrieved in scientific databases were eligible. We found that rescuers experience high levels of stress and some associations of higher levels of stress with lower resuscitation performance. Finally, few interventional studies assessed whether interventions aiming at reducing levels of stress may have a beneficial effect on resuscitation performance, but results are variable. Although the mechanisms linking stress to performance of emergency teams are still not fully understood, factors such as individual experience and self-confidence of rescuers, gender composition and hierarchy within resuscitation teams may play an important role. This review provides a targeted overview of how stress can be defined and measured, how it may influence emergency situations such as a cardiopulmonary resuscitation, and which interventions have the potential to reduce overwhelming stress.

Can women detect cues to ovulation in other women's faces?

Recent research suggests that men find portraits of ovulatory women more attractive than photographs of the same women taken during the luteal phase. Only few studies have investigated whether the same is true for women. The ovulatory phase matters to men because women around ovulation are most likely to conceive, and might matter to women because fertile women might pose a reproductive threat. In an online study 160 women were shown face pairs, one of which was assimilated to the shape of a late follicular prototype and the other to a luteal prototype, and were asked to indicate which face they found more attractive. A further 60 women were tested in the laboratory using a similar procedure. In addition to choosing the more attractive face, these participants were asked which woman would be more likely to steal their own date. Because gonadal hormones influence competitive behaviour, we also examined whether oestradiol, testosterone and progesterone levels predict women's choices. The women found neither the late follicular nor the luteal version more attractive. However, naturally cycling women with higher oestradiol levels were more likely to choose the ovulatory woman as the one who would entice their date than women with lower oestradiol levels. These results imply a role of oestradiol when evaluating other women who are competing for reproduction.

Testosterone-to-oestradiol ratio is associated with female facial attractiveness.

The relationship between facial shape and attractiveness has been extensively studied, yet few studies have investigated the underlying biological factors of an attractive face. Many researchers have proposed a link between female attractiveness and sex hormones, but there is little empirical evidence in support of this assumption. In the present study we investigated the relationship between circulating sex hormones and attractiveness. We created prototypes by separately averaging photographs of 15 women with high and low levels of testosterone, oestradiol, and testosterone-to-oestradiol ratio levels, respectively. An independent set of facial images was then shape transformed toward these prototypes. We paired the resulting images in such a way that one face depicted a female with high hormone level and the other one with a low hormone level. Fifty participants were asked to choose the more attractive face of each pair. We found that low testosterone-to-oestradiol ratio and low testosterone were positively associated with female facial attractiveness. There was no preference for faces with high oestradiol levels. In an additional experiment with 36 participants we confirmed that a low testosterone-to-oestradiol ratio plays a larger role than low testosterone alone. These results provide empirical evidence that an attractive female face is shaped by interacting effects of testosterone and oestradiol.

Is preference for ovulatory female's faces associated with men's testosterone levels?

Women's ovulation is perceivable with different senses. Already subtle face shape differences are enough to trigger men's preference for the ovulatory female. The aim of the present study is to investigate if men's testosterone level can be linked to their preference for the ovulatory female. Thirty-nine heterosexual participants were shown face pairs of which one of them was transformed to the shape of a prototype face of a woman in her luteal cycle phase and the other was transformed to the shape of a prototype face of an ovulatory woman. Participants were asked to choose the face which they perceived as being more attractive (attractiveness task), or the woman with whom they would have better chances to get a date (dating task). In both tasks, the ovulatory female was chosen more often. Testosterone was not predictive for the chosen face; regardless of testosterone level men preferred the ovulatory woman. However testosterone predicted how confident the men were with their choice. Men with lower testosterone levels were more confident with their choice than men with higher testosterone levels.

Early follicular testosterone level predicts preference for masculinity in male faces - but not for women taking hormonal contraception.

It has been shown that women's preference for masculinity in male faces changes across the menstrual cycle. Preference for masculinity is stronger when conception probability is high than when it is low. These findings have been linked to cyclic fluctuations of hormone levels. The purpose of the present study is to further investigate the link between gonadal steroids (i.e. testosterone, estradiol, and progesterone) and masculinity preference in women, while holding the cycle phase constant. Sixty-two female participants were tested in their early follicular cycle phase, when conception probability is low. Participants were shown face pairs and where asked to choose the more attractive face. Face pairs consisted of a masculinized and feminized version of the same face. For naturally cycling women we found a positive relationship between saliva testosterone levels and masculinity preference, but there was no link between any hormones and masculinity preference for women taking hormonal contraception. We conclude that in naturally cycling women early follicular testosterone levels are associated with masculinity preference. However, these hormonal links were not found for women with artificially modified hormonal levels, that is, for women taking hormonal contraception.

Men's preference for the ovulating female is triggered by subtle face shape differences.

Recent studies have revealed that there may be perceptible cues to ovulation in humans. This study aims at extending these findings by using female faces that were shape transformed towards a late follicular (fertile) and a luteal (non-fertile) prototype. Fertile prototypes were created by averaging 25 photographs taken of females during ovulation (as determined by ovulation tests); non-fertile prototypes were created by averaging 25 photographs of the same women during the luteal phase. Twenty different (new) female faces were then shape transformed towards the luteal prototype and towards the follicular prototype in 50% and 100% steps. The two 50% transforms and the two 100% transforms were paired, resulting in stimulus pairs of two different difficulties. Thirty-six male participants were asked to choose the more attractive (Task 1), the more caring (Task 2), and the more flirtatious face (Task 3). In a final task the participants were asked to choose the woman with which the participant would have better chances to get a date (Task 4). For all tasks we found a significant preference for the follicular face. In trials with a 100% transformation towards the shape of the prototype, the preference for the follicular stimulus was significantly stronger than in trials with a 50% transformation. We conclude that subtle shape differences in faces are sufficient to trigger men's preference for a woman in her fertile cycle phase.