The highs and lows of the vocal range

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“I’m always interested in some aspect of us. What drives people? Why are we the way we are?”

While some aspiring academics gravitate toward established topics or research labs, Sethu Karthikeyan, PhD, associate professor of communication science and disorders in the College of Health Professions, has taken a different path. She has spent her academic career exploring topics that pique her curiosity and that intellectually captivate her, regardless of outside interests—a path that she says has been a little more circuitous, but rewarding every step along the way.

First and foremost, Karthikeyan has used language and speech as a tool to better understand human nature. Karthikeyan says, “It’s so broad and multidisciplinary that the question is the most important thing. It drives your literature search, and you really have to delve into psychology, biology, anthropology and sociology and integrate them into your work.”

“It’s so broad, so multidisciplinary, that the question is the most important thing. It drives your literature search, and you really have to delve into psychology, anthropology and sociology and integrate them into your work.”

Most recently, she has been studying the phenomenon of vocal pitch in relation to sexual preference. As Karthikeyan explains, men, on average, have a fundamental vocal frequency (an objective measure of vocal pitch) that is five standard deviations lower than the female vocal pitch. This so-called dimorphism is not unique to humans. However, the unusually high degree of dimorphism in apes suggests that this is not just something we inherited, but has also been the target of evolutionary selection.

For Karthikeyan, the main question is: Why?

“Men with deeper voices may be attractive to potential mates because they are associated with an aspect related to health, physical strength, social competence and/or status. This may have been a female-advantageous mate preference in our ancestral habitats. This is based on Darwin’s theory of intersexual selection,” explains Sethu. “The other argument is that it may be the result of competition between males, i.e. intrasexual selection, where individuals of the same sex compete with each other for desirable resources, including mates.”

According to Karthikeyan, both mechanisms seem to play a role in why there is a dimorphism in vocal pitch – with one of these factors arguably being somewhat more pronounced, as detailed in the theoretical work of David Puts (2010) and further supported by a recent study by his team (see Aung et al., 2023).

“Interestingly, when we look at the two mechanisms together, intrasexual competition seems to be the stronger driving force. For example, lowering the pitch of men’s voices has a greater impact on perceptions of dominance than on attractiveness.”

Karthikeyan sees this review as a starting point for exploring other related research avenues, such as how social contexts can lead to change in vocal pitch and other aspects of language such as articulation and fluency, and how these can influence each other.

“It’s important to remember that social context changes the voice,” she explains. “Pitch is determined by the size of my vocal cords, but how much I tense or relax my cords, which affects pitch modulation, might depend on the context that triggers my physiological response, for example, stress levels. In addition, changes in vocal pitch seem to be linked to other psychological measures that examine your tendency to empathize with others, to give just one example.”

Karthikeyan is excited to continue to explore complex questions at the intersection of communication sciences and disorders and evolutionary psychology. She is currently studying how articulation may vary depending on cultural identity and interlocutor, and is studying how speakers with foreign and native accents accentuate or soften certain syllables in American English depending on their interlocutor. She also recently received approval, along with collaborators Glenn Geher of the Department of Psychology at SUNY New Paltz and Andrew Gallup of the Program in Behavioral Biology at Johns Hopkins University, for a book proposal that will take the form of a Handbook of Evolutionary Psychology, an edited volume to be published by Oxford University Press.

All in all, Karthikeyan has never stopped following her curiosity – setting an admirable example for her students and colleagues alike.

“I have to be very curious about the research question and make sure I have the space to think independently about everything that leads to that question without falling into the trap of blindly following the mainstream narratives. I will always ask myself: Why did I get into this in the first place?”