Pet-directed speech (PDS) is often produced by humans when addressing dogs. Similar to infant-directed speech, PDS is marked by a relatively higher and more modulated fundamental frequency (f 0) than is adult-directed speech. We tested the prediction that increasing eye size in dogs, one facial feature of neoteny (juvenilisation), would elicit exaggerated prosodic qualities or pet-directed speech. We experimentally manipulated eye size in photographs of twelve dog breeds by −15%, +15% and +30%. We first showed that dogs with larger eyes (...) were indeed perceived as younger. We then recorded men and women speaking towards these photographs, who also rated these images for cuteness. Linear mixed-effects models demonstrated that increasing eye size by 15% significantly increased pitch range (f 0 range) and variability (f 0CV) among women only. Cuteness ratings did not vary with eye size, due to a possible ceiling effect across eye sizes. Our results offer preliminary evidence that large eyes can elicit pet-directed speech and suggest that PDS may be modulated by perceived juvenility rather than cuteness. We discuss these findings in the context of inter-species vocal communication. (shrink)

Height preferences reflecting positive assortative mating for height—wherein an individual’s own height positively predicts the preferred height of their mate—have been observed in several distinct human populations and are thought to increase reproductive fitness. However, the extent to which assortative preferences for height differ strategically for short-term versus long-term relationship partners, as they do for numerous other indices of mate quality, remains unclear. We explore this possibility in a large representative sample of over 500 men and women aged 15–77 from (...) Canada, Cuba, Norway and the United States. Participants’ own heights were measured, and they indicated their height preferences for a long-term and short-term mate using graphic stimuli containing metric indices. Replicating the “male-taller norm,” participants on average preferred taller-than-average male mates, and shorter-than-average female mates. Positive assortative preferences for height were observed across sexes and samples, however the strength of these height preferences varied with relationship context for men, and not for women. Taller men preferred relatively shorter women for short-term relationships than for long-term relationships, indicating stronger assortative preferences for height in a long-term context. These results provide preliminary evidence that, in addition to mate preferences for other physical traits related to mate quality such as masculinity in the body, face, and voice, assortative preferences for height do vary as a function of expected relationship length, but this was surprisingly only observed in preferences for female height. (shrink)