A Revealing New Study [node:title]

Rats do not know how to repeat scales, but they perceive the similarity of the same note played two octaves apart, a capacity that other mammals have, in addition to humans, according to a study.

The change of octave, which allows the same note to be played lower or higher, is important for human language, recalls this work by researchers from the Institute of Acoustics Research at the Austrian Academy of Sciences.

For example, young children trying to imitate the pronunciation of a word by an adult—whose voice is too deep for their young vocal cords—spontaneously transpose the heard sound one octave lower.

Until now, one theory suggested that this ability to perceive and produce the same sound in several octaves was developed in humans to help them develop language. But also to sing in a choir.

Unless other mammals have it naturally.

That is the new theory suggested by the study published Wednesday in the journal Open Science of the British Royal Society.

“When other species vocalize they also produce harmonic information, information that includes the octave,” explains Marisa Hoeschele, who heads the biology group at the Austrian institute and co-signed the study, to AFP.

This ability, called harmonic structure, facilitates communication between individuals whose vocalizations extend over several octaves, according to experts.

“It’s important to recognize that it’s the same thing, even if the tone is different,” according to Hoeschele.

– Children and birds –

The Institute group, led by Bernhard Wagner, worked with 40 rats.

The animal first became accustomed to listening, in disorder, to a series of four notes in the same octave: E, F, F sharp and G. With the reward of a sugar pill after listening to each note.

The exercise was repeated for twenty days. Then we moved on to the testing phase itself, with a range two octaves higher. This time the series was only six notes, of which only three corresponded to those of the previous habituation phase.

This distraction disrupted the search for a reward because the rat did not expect to obtain that treat by hearing an “intrusive” note. However, when the notes were similar to those heard two octaves lower, they tried to obtain the reward.

A reaction similar to that recorded in a 1984 experiment with very young children: babies instinctively noticed, by turning their heads, the introduction of “new” notes in a melodic series initially played higher or lower.

Along the same lines, the experiment detailed this week suggests that in the case of the rat “the phenomenon of octave equivalence occurs naturally,” without initial exposure to music or training.

This rodent thus joins the dolphin and the rhesus macaque, the only two other mammals, apart from humans, that have shown an ability to perceive the equivalence of notes in several octaves.

In humans, this ability is based on a neuronal structure, recalled a previous study by Hoeschele.

“It seems that the brain is organized in a way that allows octaves to be taken into account,” according to the scientist. And it is also the case for other mammal species.

The reaction of birds, which have an ability to produce and learn songs that goes far beyond the simple identification of octaves, remains to be investigated more widely. For now, researchers have applied this Hoeschele protocol to two species, without positive results.

With information from France Media Agency / Pierre CELERIER

N. from R.: The ability to perceive the equivalence of the same note in different octaves is an interesting phenomenon that has been documented in several species of mammals, including rats, dolphins and rhesus macaques, in addition to humans. This study, conducted by researchers at the Institute for Acoustics Research at the Austrian Academy of Sciences, provides evidence that rats also possess this ability without the need for prior musical training. The equivalence of octaves is crucial for communication and could have evolutionary implications, since it suggests a common neural basis among diverse species for the perception of harmonic structure. This finding adds a new dimension to our understanding of the evolution of language and music in humans and other mammals.