In a new study published this week in the journal Biology Letters, researchers from the Max Planck Institute for Psycholinguistics and elsewhere tested untrained rhythm discrimination in harbor seals (Phoca vitulina).
A pup of the harbor seal (Phoca vitulina). Image credit: Ian Capper / CC BY-SA 2.0.
“We know that our closest relatives, non-human primates, need to be trained to respond to rhythm,” said Dr. Laura Verga, first author on the study.
“And even when trained, primates show very different rhythmic capacities to ours. But what about other mammals?”
In their research, the authors aimed to test the rhythmic abilities of harbor seals, a mammalian vocal learning species.
They first created sequences of seal vocalizations; the sequences differed in three rhythmic properties: tempo (fast or slow, like beats per minute in music), length (short or long, like duration of musical notes) and regularity (regular or irregular, like a metronome vs. the rhythm of free jazz).
They then tested 20 young seals, held at the Dutch Sealcentre Pieterburen before being released into the wild.
Using a method from human infant studies, they recorded how many times the seals turned their head to look at the sound source (behind their backs). Such looking behavior indicates whether animals (or infants) find a stimulus interesting.
If seals can discriminate between different rhythmic properties, they might look longer or more often when they hear a sequence they prefer.
The seals looked more often when vocalizations were longer, faster, or rhythmically regular.
This means that the one-year-old seals — without training or rewards — spontaneously discriminated between regular (metronomic) and irregular (arrhythmic) sequences, sequences with short vs. long notes, and sequences with fast vs. slow-paced tempo.
“Another mammal, apart from us, shows rhythm processing and vocalization learning,” Dr. Verga said.
“This is a significant advance in the debate over the evolutionary origins of human speech and musicality, which are still rather mysterious.”
“Similarly to human babies, the rhythm perception we find in seals arises early in life, is robust and requires neither training nor reinforcement.”
Verga Laura et al. 2002. Spontaneous rhythm discrimination in a mammalian vocal learner. Biol. Lett 18 (10): 20220316; doi: 10.1098/rsbl.2022.0316
Source : Breaking Science News