August 13, 2017

Getting Dogs to Listen: It's All in How You Speak

Researchers considered whether adult-directed speech, infant-directed speech, or pet-directed speech (so-called happy talk) elicits greater attentiveness in dogs, providing evolutionary insight into the human-dog relationship.
By JoAnna Pendergrass, DVM
In a study recently published in Nature’s Scientific Reports, a team of French researchers concluded that an adult dog’s attentiveness is greater with pet-directed speech (PDS) than with adult-directed speech (ADS). Such results, the researchers noted, provide evolutionary insight into the human-dog relationship and have practical implications for dog learning.

PDS is a special speech register for communication with pets. It shares similarities in prosody (vocal rhythm and sound patterns) and syntax with infant-directed speech (IDS). For example, PDS and IDS—“happy talk”—use simplified syntax and have higher frequencies. Interestingly, infants’ and dogs’ preferences for happy talk may be biological, given that mammals use higher-pitched sounds for attention and positive social engagement.

For infants, IDS reportedly enhances neural attentional processing and increases gaze duration toward adults using IDS. To date, only 1 study has evaluated PDS in dogs, in which puppies reacted more strongly to PDS than ADS. Other canine studies have reported that dogs are more likely to follow the gaze of a human who makes eye contact and uses a high-pitched voice during a greeting.  

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Testing Procedure
For this study, 63 pet dogs (44 adults, 19 puppies) of various breeds participated. First, researchers recorded adult women saying “Shall we go for a stroll?” one time each to an infant, an adult dog, and a research team member, thus representing real-life examples of IDS, PDS, and ADS, respectively. Next, each woman’s 3 sentences were organized into 1 audio clip, with sentence order randomized between the clips.

In the testing room, a female experimenter stood in front of a loudspeaker and stared straight ahead, facing the dog and its owner; the owner did not interact with the dog. Each dog heard 1 audio clip played back through the loudspeaker.

To measure attentiveness, the researchers analyzed video recordings of the testing sessions for gaze duration—how long a dog looked toward the loudspeaker. Acoustic analyses were performed to determine the effect of each speech types’ acoustic features on gaze duration.

Results
Speech type, playback order, and dog age significantly affected gaze duration:
  • Speech type (adult dogs only) – Gaze duration was longer with PDS than ADS, indicating the dogs’ increased sensitivity to PDS and their ability to discriminate between these 2 speech types. No significant differences were observed between IDS and ADS, which surprised the researchers.
  • Playback order (adult dogs only) – For PDS, gaze duration was shortest when PDS was played third. For IDS, gaze duration was longest when IDS was played first. Playback order did not affect gaze duration for ADS.
  • Dog age Gaze duration was longer in puppies than in adult dogs, likely because puppies are generally very attentive to human vocalizations.
Other variables, including dog sex and the presence of children at home, did not significantly affect gaze duration. Also, speech type and playback order had no significant effect on puppies’ gaze duration, signifying puppies’ overall high attentiveness to human speech sounds.

Regarding acoustic features, the researchers observed a relationship between attentiveness and fundamental frequency (high or low sound of a person’s voice)—gaze duration increased as the women’s voices rose higher. This finding provides more evidence that, compared with ADS, which has a lower frequency, PDS is better able to elicit a dog’s attention.

Practical Applications
“From a practical perspective,” the researchers wrote, “our study provides support for the use of PDS by dogs’ instructors as a key tool to facilitate learning.” More specifically, the pitch modulations in PDS can be used to emphasize key words, enhancing a dog’s learning and comprehension.

 
Dr. JoAnna Pendergrass received her Doctor of Veterinary Medicine degree from the Virginia-Maryland College of Veterinary Medicine. Following veterinary school, she completed a postdoctoral fellowship at Emory University’s Yerkes National Primate Research Center. Dr. Pendergrass is the founder and owner of JPen Communications, a medical communications company.

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