Comparative Meows

The following is an article from The Annals of Improbable Research.

Studies of varied meows here and there, now and then
by Alice Shirrell Kaswell, Improbable Research staff

Human beings struggle to understand what, if anything, cats are communicating or trying to communicate. Here are reports about some of those struggles.

Schötz on Meows
Susanne Schötz, at Lund University, Sweden, together with various colleagues, studies many aspects of cat meowing. One of those colleagues, Robert Eklund, maintains a web site devoted to purring research.

“A Study of Human Perception of Intonation in Domestic Cat Meows,” Susanne Schötz and Joost van de Weijer, Proceedings of the 7th International Conference on Speech Prosody, Dubin, Ireland, May 20-23, 2014. (Thanks to investigator Daniela Müller for bringing this to our attention.) The researchers explain:

This study examined human listeners’ ability to classify domestic cat vocalisations (meows) recorded in two different contexts: during feeding time (food-related meows) and while waiting to visit a veterinarian (vet-related meows). A pitch analysis showed a tendency for food-related meows to have rising F0 contours, while vet-related meows tended to have more falling F0 contours. 30 listeners judged twelve meows (six of each context) in a perception test... Listeners also reported that some meows were very easy to classify, while others were more difficult. Taken together, these results suggest that cats may use different intonation patterns in their vocal interaction with humans, and that humans are able to identify the vocalisations based on intonation...

The participants who were familiar with cats were not only more often correct in their answers, they were also more confident in their answers.

Schötz and van de Weijer also present a terse taxonomy of cat mouth sounds:

Cat vocalisations are generally divided into three major categories: (1) sounds produced with the mouth closed (murmurs), such as the purr, the trill, and the chirrup; (2) sounds produced with the mouth open(ing) and gradually closing, comprising a large variety of meows with similar [A:ou] vowel patterns; and (3) sounds produced with the mouth held tensely open in the same position, i.e. sounds often uttered in aggressive situations, including growls, yowls, snarls, hisses, spits, and shrieks.

Schötz on Chirp, Chatter, Tweet, and Tweedle
“A Phonetic Pilot Study of Chirp, Chatter, Tweet and Tweedle in Three Domestic Cats,” Susanne Schötz, Proceedings of Fonetik 2013, Linköping University, Sweden, 2013, pp. 65-68. The author reports:

This study collected 257 vocalisations from three domestic cats when they were watching birds through the window. The sounds were subdivided into the types chatter, chirp, tweet, and tweedle, and analysed for duration and F0. Variation was found within and between these types as well as within and between the three cats in both duration and F0. A tentative taxonomy of prey-observing cat vocalisations is suggested based on words used for bird sounds.

Detail from the study “A Phonetic Pilot Study of Chirp, Chatter, Tweet and Tweedle in Three Domestic Cats.”

Phonetic Study of Vocalisations in Three Cats
“A Phonetic Pilot Study of Vocalisations in Three Cats,” Susanne Schötz, Proceedings of Fonetik 2012, Department of Philosophy, Linguistics and Theory of Science, University of Gothenburg, Sweden. The author reports:

538 vocalisations from three domestic cats were collected and used in a phonetic pilot study in order to test some recording and analysis methods normally used with human speech. Based on auditive analysis, the vocalisations were categorised into five types and analysed for duration and F0. The most common type was a combined murmur and miaow... Neither the recording techniques nor the analysis tools used here were judged to be optimal for cat vocalisations.

Acoustic Analysis of Purring in Four Cats
“A Comparative Acoustic Analysis of Purring in Four Cats,” Susanne Schötz and Robert Eklund, Proceedings of Fonetik 2011, Speech, Music and Hearing, KTH, Stockholm, TMHQPSR, 51. Department of Speech, Music and Hearing, KTH, Stockholm. The authors report:

This paper reports results from a comparative analysis of purring in four domestic cats. An acoustic analysis describes sound pressure level, duration, number of cycles, and fundamental frequency for egressive and ingressive phases. Significant individual differences are found between the four cats in several respects...

[It] is not known exactly how purring is produced, and the term as such has been used quite liberally in the literature... A number of different purring theories are found in the literature. McCuiston [“Feline Purring and Its Dynamics,” W.R. McCuiston, Veterinary Medicine/Small Animal Clinician, vol. 61, 1966, pp. 562–566] suggested that purring was hemodynamic and that the sound consequently emanated from the bloodstream running through the thorax. This theory was proven wrong by Stogdale & Delack (1985).

To the best of our knowledge, this paper constitutes the first comparative and quantitative report of purring in domestic cats.

One of the four cats in Schötz and Eklund's study. See the others at Eklund's website. (YouTube link)

Moelk on Meows
Mildred Moelk, in Rochester, New York, performed an early solo attempt at analyzing the sounds emanating from several cats to which she had access.

“Vocalizing in the House-Cat: A Phonetic and Functional Study,”  Mildred Moelk, American Journal of Psychology, vol. 57, no. 2, 1944, pp. 184–205. The author writes:

The house-cat, unlike man, has enforced upon it no model of traditional language and no standard of correct pronunciation to which it must conform. Variety of phonetic form in the vocalizing of these animals is due to an unstudied modification of a voiced column of air during inhalation or exhalation, by means of tensional changes in the mouth and throat, by speed and energy of the column of air, and by the extent, time, and rate of the opening of the mouth. Thus vocalization basically derives its form from the constitution and the physiology of the cat.

Nicastro’s Classification of Meows
Nicholas Nicastro, at Cornell University, Ithaca, New York, produced three meow studies during the period 2002-2004.

“Classification of Domestic Cat (Felis catus) Vocalizations by Naive and Experienced Human Listeners,” Nicholas Nicastro and Michael J. Owren, Journal of Comparative Psychology, vol 117, no. 1, March 2003, pp. 44-52. The authors explain:

To test for possible functional referentiality in a common domestic cat (Felis catus) vocalization, the authors conducted two experiments to examine whether human participants could classify meow sounds recorded from 12 different cats in five behavioral contexts. In Experiment 1, participants heard single calls, whereas in Experiment 2, bouts of calls were presented. In both cases, classification accuracy was significantly above chance, but modestly so... Overall, participants performed better in classifying individual calls if they had lived with, interacted with, and had a general affinity for cats. These results [suggest] that meows are nonspecific, somewhat negatively toned stimuli that attract attention from humans.

Nicastro’s Classification of Domestic vs. Wild Meows
“Perceptual and Acoustic Evidence for Species-Level Differences in Meow Vocalizations by Domestic Cats (Felis catus) and African Wild Cats (Felis silvestris lybica),” N. Nicastro, Journal of Comparative Psychology, vol. 118, no. 3, September 2004, pp. 287-296. (Thanks to Paul Smolen for bringing this to our attention.) Nicastro explains:

Human listeners at all levels of experience and affinity for cats rated domestic cat meows as far more pleasant sounding than wild cat vocalizations. These results are consistent with a model of cat domestication that posits selective pressure on meows based on human perceptual biases.

Nicastro’s Classification of Human Responses to Meows
“Acoustic Correlates of Human Responses to Domestic Cat (felis catus) Vocalizations,” Nicholas Nicastro, Journal of the Acoustical Society of America, vol. 111, no. 5, May 2002, p. 2393. The abstract, which appears to be all that was published, says:

As part of ongoing research on coevolution of vocal communication between humans and domestic cats, perceptual data were collected on participants as they listened to recorded cat vocalizations. In experiment 1, human subjects were asked to rate the pleasantness of 100 meows along a 7-point scale, from most to least pleasant. In experiment 2, a different group of participants was asked to rate the urgency of the same meows along a 7-point scale, from most to least urgent. Linear regression analysis of the results showed a strong inverse correlation between pleasantness and urgency.

Inside the Purrs
“The Cry Embedded Within the Purr,” Karen McComb, Anna M. Taylor, Christian Wilson, and Benjamin D. Charlton, Current Biology, vol. 19, no. 13, July 14, 2009, pp. R507-R508. The authors, at the University of Sussex, UK, and at Zoo Atlanta, Atlanta, Georgia, USA, report:

Despite widespread interest in inter-specific communication, few studies have examined the abilities of companion animals to communicate with humans in what has become their natural environment—the human home. Here we report how domestic cats make subtle use of one of their most characteristic vocalizations—purring—to solicit food from their human hosts, apparently exploiting sensory biases that humans have for providing care. When humans were played purrs recorded while cats were actively seeking food at equal amplitude to purrs recorded in non-solicitation contexts, even individuals with no experience of owning cats judged the solicitation purrs to be more urgent and less pleasant. Embedded within the naturally low-pitched purr, we found a high frequency voiced component, reminiscent of a cry or meow, that was crucial in determining urgency and pleasantness ratings. Moreover, when we re-synthesised solicitation purrs to remove only the voiced component, paired presentations revealed that these purrs were perceived as being significantly less urgent. We discuss how the structure of solicitation purrs may be exploiting an inherent mammalian sensitivity to acoustic cues relevant in the context of nurturing offspring.

Detail from the study “The Cry Embedded Within the Purr.”

Discouragement on Meows
“No Meaning Required: Abandoning the Quest for a Language Grail in Animal Communication,” Drew Rendall and Michael J. Owren, (submitted to) Behavioral and Brain Sciences. The authors, at the University of Lethbridge, Alberta, Canada, and Cornell University, Ithaca, New York, explain:

Theoretical approaches to animal communication presented over several decades have been heavily influenced by linguistic analogy. As a result, research has been preoccupied with the “meaning” of animal signals, characterizing communication as encoding, transmission, and decoding of information. While historically important, we believe that this overarching “information transmission” perspective is flawed and should be abandoned.

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The article above is from the May-June 2015 issue of the Annals of Improbable Research. You can download or purchase back issues of the magazine, or subscribe to receive future issues. Or get a subscription for someone as a gift!

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