The perception of rhythm is one of the fundamental human cognitive abilities.

Whether in music or speech, rhythmic structures draw attention.

When we hear a certain pattern, our motor system is able to synchronize with that type of input.

For example, in all cultures people dance to the rhythm of the music.

But neuronal activity is also synchronized in certain frequency bands to external auditory stimuli.

This ability for rhythmic synchronization is considered a universal human quality.

However, it has not yet been clarified where humans got this from.

In order to explore the roots of evolutionary biology in more detail, scientists are therefore looking at the animal kingdom – and investigating whether other animals have similar rhythmic abilities.

The results of a study that was carried out with seals now provide new information about their development.

It was published in the journal Biology Letters.

Scientists from the Max Planck Institute for Psycholinguistics in Nijmegen, the Netherlands, wanted to find out to what extent young seals have the ability to spontaneously, i.e. without prior training, distinguish sound sequences based on their rhythmic properties.

In order to test this, sound recordings were processed with the call sounds of conspecifics and manipulated with regard to three different rhythmic parameters: The tempo (slow versus fast), the note or call length (short versus long note) and the regularity (rhythmic versus a-rhythmic structure) of the call sounds changed.

Methods from infant research

To find out whether the seals recognize the differences between the manipulated sequences, the scientists used a method that originally comes from developmental psychology and is used there to research auditory preferences in infants.

In the so-called "head-turning paradigm" it is observed how often and for how long the infant - in this case the seal - turns its head in the direction of the stimulus.

This is interpreted as a measure of how interesting the stimulus is and allows conclusions to be drawn about cognitive processing.

In cooperation with the Danish Seal Center in Pieterburgen, 20 harbor seals that were around one year old were tested using this method.

The results showed that the seals did in fact have preferences for different rhythmic characteristics.

The seals were more attentive to rapid succession of sounds than to slow successions.

They also preferred the tone sequences in which the calls were longer.

Likewise, the seals turned their attention to the sound source more often when the calls exhibited a rhythmic regularity rather than an arrhythmic sequence.

The authors conclude that young seals have the ability to discriminate auditory stimuli based on their rhythmic properties.

For the scientists, this is crucial evidence that could help clarify important questions: "This is a significant step forward in the debate about the evolutionary origins of human language and musicality, which are still quite a mystery. Similar to human babies the rhythm perception that we find in seals early in life. It is robust and requires neither training nor rewards," says Laura Verga, leader of the study. According to the author, the next step is to investigate whether the seals also respond to such vocalizations are sensitive to rhythms that do not come from their own kind.

Other mammal species will also be studied.

This should contribute both to a better understanding of the evolutionary development of rhythmic abilities and to comparative research into whether the sensitivity to rhythm is a question of common ancestry or whether it is a trait that has arisen several times independently in the history of development and in several species occurs.