Predictive and tempo-flexible synchronization to a visual metronome in monkeys

Area of Science:

• Neuroscience
• Comparative Cognition
• Auditory Perception

Background:

• Beat synchronization is crucial for human music perception and performance.
• Spontaneous beat synchronization is observed in vocal learning species but not typically in vocal non-learners like macaques.
• Previous studies suggested macaques' rhythmic tapping was reactive, not predictive, raising questions about their capacity or motivation.

Purpose of the Study:

• To investigate whether macaques (vocal non-learners) possess the capacity for predictive and tempo-flexible synchronization to a beat.
• To differentiate between a lack of capacity versus a lack of motivation for predictive synchronization in monkeys.
• To compare synchronization strategies between monkeys and humans.

Main Methods:

• Trained macaques to perform synchronized eye movements (saccades) to a visual metronome.
• Varied reward contingencies to elicit predictive versus reactive saccades.
• Tested generalization to novel tempi and assessed tempo maintenance.
• Compared monkey performance with human participants performing reactive saccades.

Main Results:

• Monkeys successfully generated predictive saccades to a visual metronome when rewarded for predictive movements.
• This predictive synchronization generalized to new tempi, and monkeys could internally maintain the tempo.
• Monkeys flexibly switched between predictive and reactive saccade strategies based on reward structure.
• Humans, when instructed to make reactive saccades, often unintentionally produced predictive movements.

Conclusions:

• Vocal non-learners, like macaques, possess the neural capacity for predictive and tempo-flexible synchronization to a beat.
• The spontaneous absence of this behavior in non-vocal learners may stem from a lack of intrinsic motivation rather than inability.
• Findings highlight potential evolutionary divergence in the motivation for musicality across species.