This preliminary study aimed to explore whether language usage could influence mate selection, which could support the possibility that language evolution has been driven by sexual selection. This is the first study to directly examine a potential evolutionary bias for the usage of different types of linguistic forms. In our experiment a typical mate selection scenario was created for female participants using male faces of average attractiveness22,23,40,41,43 which were additionally paired with verbal compliments varying in terms of figurativeness and topic. Using this approach differences in attractiveness rating scores should be primarily driven by linguistic variance and topic rather than by the faces per se. The findings confirm our hypotheses that in a courtship situation where compliments serve as a sexual display of mate quality, women show a preference for metaphors, particularly novel ones, in verbal structure. In agreement with previous studies6,7,8,9 we found that the use of metaphorical as opposed to prosaic language by men in compliments is perceived by women as indicative of creativity and intelligence. The preference observed for metaphorical compliments targeting a woman’s appearance compared to possessions may be indicative that this generates greater sexual attraction towards a potential mate. Furthermore, this impact of language usage in compliments on attractiveness judgments does not vary with women’s love style attitudes. Interestingly, while participants were subsequently unable to remember the faces paired with different types of compliments better than chance, when the faces were presented alone, attraction ratings for those previously paired with metaphorical compliments continued to be rated as the most attractive. This indicates that the previous association with such metaphorical compliments resulted in an unconscious attraction bias towards these individuals.

Overall, these results support our first hypothesis that men who use metaphorical compliments, particularly novel ones, are perceived as more attractive by women than men who produce more prosaic literal compliments. Previous studies have revealed that compared with other mate qualities women, in contrast with men, prefer creativity and intelligence rather than physical attractiveness44,45,46,47, and for the compliments used in our current study women did indeed perceive those which were figurative as indicating higher intelligence in a man than literal expression compliments. Interestingly use of figurative as opposed to literal language in compliments was not significantly linked to perceived dominance which is also known to influence male attractiveness. Thus the type of language use during interactions with a prospective mate may provide a key indicator of a male’s intelligence and creativity although not dominance. We tend to form very rapid impressions about a person’s attractiveness in social contexts42 and thus for women, cues from language usage during initial encounters may provide a rapid first assessment of a potential mate’s intellectual and creative abilities. The current study deliberately paired verbal compliments with the faces of men of average attractiveness in order to optimize the chances of showing an impact of language usage on perceived attractiveness. It therefore remains to be seen whether metaphorical language usage would also increase the attractiveness of individuals with either low or high facial attractiveness.

We tried in the current study to control for possible confounding contributions of non-specific factors unrelated to language on altered attractiveness ratings. The face stimuli used were deliberately standardized and of average attractiveness in order to render them as homogeneous as possible and pairing of faces with specific compliment sentences was entirely random across subjects. We found no evidence for increased attractiveness ratings of face pictures per se when they were presented for a second time, and therefore more familiar. While a previous study has reported that familiarization with unfamiliar faces through repeated exposure can lead to increased attraction ratings48, this used a smaller number of faces with more emotive, smiling faces and also a longer exposure time with more frequent presentations than in our current study. It could perhaps be argued that the differential novelty of the sentences paired with faces in the first session might have in some way resulted in the faces associated with them exhibiting increased familiarity/depth of encoding and therefore continuing to be rated as more attractive. However, while the faces originally paired with novel metaphors targeting appearance did indeed receive the highest attractiveness ratings in the second session, those paired with conventional metaphors were significantly less than for literal expression compliments, despite being more novel. Similarly, for compliments targeting possessions, attractiveness ratings for faces associated with novel metaphors became significantly less than those for the more familiar conventional ones in session two (see Fig. 4b). Finally, we also found no evidence for faces associated with either novel or conventional figurative language compliments being better remembered than those paired with literal expressions. We therefore consider that at this stage the most parsimonious explanation for our findings is in terms of the impact of the language content of the verbal compliments on attractiveness ratings of the face pictures rather than as a result of factors unrelated to language such as differential familiarity/depth of encoding. However, further experiments will be needed to completely disentangle all possible contributing factors.

Our second hypothesis that men who complimented women’s appearance as opposed to her possessions would be perceived as more attractive is also supported since in both experimental sessions attractiveness ratings were higher for the faces of individuals paired with compliments targeting appearance. Since ratings of the general social relevance and valence of the compliments targeting possessions as opposed to appearance did not differ significantly it is unlikely that differences in attraction ratings in the main experiment can simply be explained in terms of greater social appropriateness or positivity. The importance of compliment topic can however be both gender- and context- dependent49,50,51. For example, in a same-sex unstructured context women preferred compliments on their appearance whereas men preferred them on their sporting performance50. However, our study corroborates previous findings that personal appearance is the most preferred target for compliments in opposite-sex interactions among Chinese people52,53. Since compliments between the sexes on appearance can easily develop into “flirtation”48, they tend to indicate direct sexual intent and are thus likely to provoke reciprocal compliments by recipients. Moreover, the finding that the impact of novel metaphors is weaker when the compliment topic is less sexually directed might indicate that “sexual selection shapes language’s content more than its form”4. Thus we found in session one that compliments on appearance were consistently more effective in increasing attractiveness ratings compared to those on possessions, regardless of the type of language used, although in the second session where only faces were viewed this was only the case for individuals previously associated with novel metaphor usage. Possibly novel metaphors targeting appearance might be viewed as particularly “flirtatious” relative to conventional ones, although this would require verification.

Our third hypothesis that the observed attraction bias for the figurativeness or topic of compliments would be greater during the fertile phase of the menstrual cycle was only partially supported. High conception risk greatly increased men’s attractiveness in the eyes of women in a relationship if appearance was praised, although there was a tendency for them to find men who complimented their appearance more attractive across the whole cycle. For the single women on the other hand this preference was exhibited only by those with a low conception risk. The finding for women in a relationship possibly indicates their extra-pair interest when fertile, i.e. for the sake of promoting good genes in their offspring, and thus they show greater attraction for males other than their partners with qualities indicative of having good genes when near ovulation54,55. However, the single women with high conception risk showed equivalent preference for the men who paid compliments regardless of topic. This suggests that when the single women were in their fertile phase they were not particularly sensitive to the type of compliment given. Possibly this may reflect a tendency to view men who pay any compliments to women as being more likely to show sexual interest in them. On the other hand during the luteal phase when there is no likelihood of conception, and sexual interest is reduced, then they are more selective and compliments targeting appearance become more salient and attractive to them.

Although relationship status influenced the impact of menstrual cycle phase on the attractiveness of compliments, our overall findings showed that attractiveness judgments exhibited a very similar preference pattern for metaphors in both the singles and relationship groups. The only significant difference between the groups was that women in a relationship gave slightly higher ratings than single women did to novel metaphorical compliments in session one, although not in session two. This might suggest that women in a relationship paid more attention to the verbal compliments presented in session one than single women did. This conclusion is supported by a previous study showing that women in a relationship showed a greater attentional bias to flirtatious courtship distractors than single women did56. Single women generally exhibited less sensitivity towards compliment topic and form than the women in relationship, particularly in terms of the preference for novel metaphors.

The fact that Pragma (practical) and Storge (friendship-based) love style attitudes constituted 59.65% and 45.61% of the participants in our study may reflect both the participants’ sex57,58 and Chinese culture59. This finding is consistent with the report that Chinese women, relative to their western counterparts, view love as a companionship and place marriage over love59,60,61. Since few correlations were found between the language types of compliments and love attitudes, the preference for use of figurative language in courtship may extend across all love styles and not be modulated by whether individuals exhibit a more pragmatic or romantic love style. However, this would need to be investigated in more detail in a future larger study.

Importantly, the findings in the current study support the view that an attraction bias towards individuals using figurative language for paying compliments is essentially an unconscious one. Thus the female participants in the study provided no overt evidence of improved recognition memory for such individuals or the actual compliments they used, but nevertheless exhibited an attraction bias towards them when presented with their face pictures alone. This is consistent with other research demonstrating the power of “first impressions” where altered behavioral preferences for face pictures of individuals paired with verbal statements about their attributes also failed to result in their subsequently becoming more memorable42. Thus both language use and information about an individual’s personal attributes can profoundly alter their perceived attraction, but without someone necessarily being consciously aware of their bias towards them. This is similar in many ways to the influence of “sexual imprinting” where individuals exhibit a learned, but unconscious, attraction bias either towards (positive), or against (negative) specific visual or odor characteristics associated with an opposite sex parent or caregiver62,63.

There are some limitations for this preliminary study. Firstly, we did not carry out hormone assays to confirm the accuracy of estimations based purely on menstruation dates and self-reported cycle length. Additionally, a within-subject design where women were tested twice at different stages of their cycle may have been more effective in demonstrating menstrual cycle effects. Secondly, in terms of demonstrating effects of relationship status we combined data from single individuals who had both no experience of previous love relationships and those who had had the experience in the past. While we found no significant difference between these two types of individuals in terms of attraction ratings we cannot rule out the possibility that prior love experience might have had some effects. Finally, the current study also only included possessions and facial appearance as compliment topics and further studies need to investigate a wider range of targets including both visual and personality attributes as well as cultural influence64 and flirtatiousness of language usage48.

In summary the current study has provided preliminary experimental support for the possibility that language evolution in terms of figurativeness may have been influenced by its role in signaling reproductive fitness in the context of mate selection. Future more extensive studies are required to explore this intriguing possibility more fully.