At 27.9 °C, roughly equal numbers of female and male turtles will emerge from the nests of the Chinese pond turtle Mauremys reevesii. Slightly warmer, and more females will hatch; a little cooler, and there will be more males.Reciprocation of attraction—people’s tendency to like those who like them—may encourage the initiation of relationships with targets of interest1. Immediately reciprocating another person’s expression of liking, however, may not be the most effective strategy for attracting mates. Indeed, people who are too easy to attract may be perceived as more desperate and thus as less valuable and appealing than those who do not make their romantic interest apparent right away.
And yet, within the dating realm, there is little consensus on whether playing hard to get works2. In an attempt to entice prospective romantic partners, some people may attempt to induce these potential partners to chase them, as they believe that this will heighten their seeming desirability. Other people, however, are reluctant to deploy this strategy because they worry that it may backfire, driving prospective partners away out of fears of rejection.
In our recent research3, we investigated whether perceiving a prospective romantic partner as hard-to-get instigated sexual desire for this partner and whether viewing this person as a more valued mate explained this effect. Specifically, in three studies, participants interacted with another research participant of the other sex, who was in reality a confederate (a member of the research team). Then, participants rated the extent to which they felt the confederate was hard to get, their perceptions of the confederate’s mate value (e.g., “I perceive the other participant as a valued mate”), and their desire to engage in various sexual activities with the confederate.
In Study 1, participants who agreed to take part in a study of online interactions between prospective partners created an online profile by uploading their picture and reporting where they live, what they study, their hobbies, and their selectivity in choosing mates. In doing so, participants were asked to choose one of two options that best represented their selectivity in choosing mates: selective or less selective. Then, participants read the other participant's profile. All participants read the same profile, which presented the same information requested from the participants (the confederate's residential city, major study, hobbies, and selectivity).
Half of the participants viewed a profile that indicated that the confederate was selective in choosing mates and half of them viewed a profile of a less selective confederate. Participants then interacted with the confederate over Instant Messenger. We found that participants who interacted with potential partners whose online profile indicated that they were selective in choosing mates (and thus more difficult to attract) perceived them to be more valued and thus more desirable as partners, compared to participants who interacted with less selective partners (and thus easier to attract).
In Study 2, we explored another factor that can render individuals hard to get—the efforts invested in pursuing them—and whether such efforts would inspire heightened sexual interest. For this purpose, participants were manipulated to exert (or not) real efforts to attract the confederate during face-to-face interactions. In particular, participants were informed that they would be engaging in a face-to-face conversation with another participant (a confederate). The experimenter instructed participants and confederates to discuss their preferences in various life domains and presented a list of 10 questions (e.g., “To what extent do you prefer intimate recreation over mass entertainment?”; “To what extent do you like to cuddle with your partner while sleeping?”). The confederate expressed a different preference than that of the participants to 7 out of the 10 questions.
Participants in the hard-to-get condition were told to try and resolve their disagreements. Using a fixed script, the confederates gradually let themselves be convinced by the participants and eventually expressed agreement with the participant’s position. In this way, we sought to make participants feel that they had invested efforts in convincing the confederate and that their efforts were eventually successful.
In the no-effort condition, participants were only instructed to express their preferences and explain their point of view without trying to resolve the differences, such that participants did not feel that the discussion involved exerting efforts to convince the confederate. The findings replicated and extended those of Study 1, showing that not only selectiveness but also efforts invested in mate pursuit yield similar results, rendering potential partners perceived as more valued and sexually desirable.
In Study 3, we investigated whether the predicted effect of being hard to get would generalize to online interactions that unfolded relatively spontaneously. In addition, we examined whether being hard to get would increase not only prospective partners’ sexual desirability but also the efforts devoted to seeing them in the future. To do so, participants conversed with the confederate using Instant Messenger in a "get to know each other" chat. At the end of the chat, we asked participants to leave one final message for the confederate.
We coded these messages for efforts made to interact again with the confederate by counting in each message participants' expressions of romantic interest and desire for future interaction—for example, complimenting the confederate, flirting with him/her, asking him/her for a date. We found that interacting with prospective partners who were perceived as hard to get not only enhanced these partners’ mate value and desirability, but was also translated into investment of concrete efforts to see them in the future.
Overall, our research demonstrates how and why being hard to get may set the ground for a successful mate pursuit, affecting interpersonal perceptions in a way that can facilitate relationship initiation. Using tactics that make prospective partners hard to get (e.g., exhibiting selectivity in choosing mates) enhances their sexual desirability because it serves as a marker of mate value. Specifically, being hard to get signals that potential partners are worth pursuing because they have other mating alternatives and therefore can afford to limit their availability.
Developing reptile embryos that have temperature-dependent sex determination were long thought to passively accept their weather-based fate. But now, new research suggests that at least in M. reevesii, embryos can move around to find slightly cooler or warmer regions within their eggs, and thereby have some control over the sex they develop into. The authors propose that this ability may help offset drastic, population-wide shifts in sex ratios that are occurring due to climate change. The findings appear today (August 1) in Current Biology.
“I find it fascinating that [embryonic movements] may be an important contributor to the production of equal numbers of males and females at intermediate conditions in the wild,” writes evolutionary biologist Nicole Valenzuela of Iowa State University to The Scientist in an email. “It is quite a novel finding.”
Behavioral ecologist Wei-Guo Du of the Institute of Zoology at the Chinese Academy of Sciences in Beijing and his colleagues found in 2011 that turtle embryos can move towards warmer regions of their eggs, and suspected that this could influence offspring sex. However, other researchers have since challenged this idea, arguing that there isn’t a strong enough thermal gradient across reptile eggs and that the embryos simply don’t have the ability to move.
To test their hypothesis, Du and his colleagues started by measuring how much temperatures can vary between the two ends of an egg. In eggs they dug up from a dozen turtle nests by an outdoor pool at a commercial turtle farm they found “dramatic” differences in temperature, Du says: the difference was 1.2 °C on average and could be as high as 4.7 °C.
To find out if developing turtle embryos cold move towards warmer or cooler regions within the egg, the scientists disrupted their ability to sense temperature by applying to the outside of the egg a chemical called capsazepine, which reportedly blocks ion channels that act as heat sensors in crocodiles and lizards.
In the lab, the team placed a heat source at one end of the capsazepine-treated eggs, held a light to the eggs so they could view their contents, and marked the embryos’ position within the egg. After one week, they observed that these embryos had barely budged, whereas untreated embryos had moved by a few millimeters towards the warmer end of the egg.
To see if this would have any effect on the sex ratio of clutches, the team removed eggs from around 20 nests, each with eight eggs on average. They treated half of them with capsazepine, and placed all of them back into nests at random. Three months after hatching, they sexed the animals by inspecting their gonads.
The effect of capsazepine relative to untreated eggs varied by season. When the eggs developed in colder months, the majority of both treated and untreated eggs hatched as males, and in hot months nearly all of them were female.
But when ambient temperatures hovered around 28 °C—the “pivotal” temperature at which males turn female—the difference between untreated and treated eggs became apparent: capsazepine-treated eggs skewed heavily male when the temperatures dipped a little below that temperature, and female at slightly warmer temperatures. Untreated eggs, on the other hand, appeared to resist this shift, producing a 1:1 sex ratio.
The authors propose that untreated embryos—which have the ability to sense temperature—are offsetting heat variations by moving towards the cooler end of the egg at warmer temperatures, and vice versa. This expands the range of temperatures at which both sexes can exist in relatively even ratios. “Natural selection favors behaviors that increase an individual’s viability—in this case, by enabling it to develop as the sex that will benefit most from the current conditions,” Du writes in an email.
But this only works when ambient temperatures are close to “pivotal” temperatures, and as long as temperatures vary across the egg. It’s “one potential mechanism” that complements other strategies turtles have in place to handle climatic variations, such as mothers’ choice of shadier or deeper nests, Du explains.Top things to know:
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