Horses are sensitive to baby talk: pet-directed speech facilitates communication with humans in a pointing task and during grooming

Abstract

Pet-directed speech (PDS) is a type of speech humans spontaneously use with their companion animals. It is very similar to speech commonly used when talking to babies. A survey on social media showed that 92.7% of the respondents used PDS with their horse, but only 44.4% thought that their horse was sensitive to it, and the others did not know or doubted its efficacy. We, therefore, decided to test the impact of PDS on two tasks. During a grooming task that consisted of the experimenter scratching the horse with their hand, the horses (n = 20) carried out significantly more mutual grooming gestures toward the experimenter, looked at the person more, and moved less when spoken to with PDS than with Adult-directed speech (ADS). During a pointing task in which the experimenter pointed at the location of a reward with their finger, horses who had been spoken to with PDS (n = 10) found the food significantly more often than chance, which was not the case when horses were spoken to with ADS (n = 10). These results thus indicate that horses, like certain non-human primates and dogs are sensitive to PDS. PDS could thus foster communication between people and horses during everyday interactions.

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Animal Cognition (2021) 24:999–1006
https://doi.org/10.1007/s10071-021-01487-3
ORIGINAL PAPER
Horses are sensitive tobaby talk: pet‑directed speech facilitates
communication withhumans inapointing task andduringgrooming
LéaLansade1 · MilénaTrösch1· CélineParias1· AliceBlanchard1· ElodieGorosurreta1· LudovicCalandreau1
Received: 4 December 2020 / Revised: 29 January 2021 / Accepted: 5 February 2021 / Published online: 18 March 2021
© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2021
Abstract
Pet-directed speech (PDS) is a type of speech humans spontaneously use with their companion animals. It is very similar to
speech commonly used when talking to babies. A survey on social media showed that 92.7% of the respondents used PDS
with their horse, but only 44.4% thought that their horse was sensitive to it, and the others did not know or doubted its efficacy.
We, therefore, decided to test the impact of PDS on two tasks. During a grooming task that consisted of the experimenter
scratching the horse with their hand, the horses (n=20) carried out significantly more mutual grooming gestures toward the
experimenter, looked at the person more, and moved less when spoken to with PDS than with Adult-directed speech (ADS).
During a pointing task in which the experimenter pointed at the location of a reward with their finger, horses who had been
spoken to with PDS (n=10) found the food significantly more often than chance, which was not the case when horses were
spoken to with ADS (n=10). These results thus indicate that horses, like certain non-human primates and dogs are sensitive
to PDS. PDS could thus foster communication between people and horses during everyday interactions.
Keywords Motherese· Infant-directed speech· Dog-directed speech· Emotion· Positive affect
Introduction
Pet-directed speech (PDS) is a type of speech humans spon-
taneously use with their companion animals. According to
a survey posted on social media, 92.7% of the respondents
used PDS with their horses (see SI). PDS is characterized by
a high-pitched voice, a wide pitch range, slow rate, simple
syntax and semantics, and high repetition of words com-
pared to Adult-directed speech -ADS- (Ben-Aderet etal.
2017; Benjamin and Slocombe 2018; Jeannin etal. 2017;
Lesch etal. 2019). In this way, it is similar to speech used
with babies commonly called “baby talk”, “fatherese”,
“motherese” or “Infant-directed speech” (IDS) and which
is known to convey speaker affect and capture the infant’s
attention (review: Saint-Georges etal. 2013). These types
of speech contain a positive emotional valence compared to
ADS which is more neutral (Singh etal. 2002).
Other than humans, several species appear to be sensitive
to this kind of speech. PDS enables dogs’ attention to be
attracted (Ben-Aderet etal. 2017) and kept for longer than
ADS (Jeannin etal. 2017). PDS also appears to encourage
referential communication demonstrated in a pointing task
in which dogs searched longer for food indicated by pointing
in an empty location when the experimenter spoke in a high-
pitched voice than in a low-pitched imperative voice (Schei-
der etal. 2011). PDS also fosters human-animal relations as
dogs interacted more with an experimenter who had previ-
ously used PDS rather than ADS (Benjamin and Slocombe
2018). In addition, effects on memory have been reported in
infant rhesus macaques, which after exposure to PDS during
the encoding of visual information show improved long-term
memory performance (Slonecker etal. 2018).
In horses, no experiments have tested the impact of PDS.
And in the survey cited above, only 44.4% of the respondents
thought that their horse was sensitive to it (17.4% thought
that it was not and 38.2% did not know, see SI). However,
we know that this species is highly sensitive to our emotions,
and in particular positive emotions, a key aspect of PDS.
They are capable of cross-modal recognition of human joy,
in associating a joyful voice with the corresponding facial
expression (Nakamura etal. 2018; Trösch etal. 2019a).
Moreover, when they hear joy expressed by a human, their
heart rate decreases, and they are more relaxed than when
* Léa Lansade
lea.lansade@inrae.fr
1 PRC, INRAE, CNRS, IFCE, University Tours,
37380Nouzilly, France
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