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

Abstract

Predictive and tempo-flexible synchronization to an auditory beat is a fundamental component of human music. To date, only certain vocal learning species show this behaviour spontaneously. Prior research training macaques (vocal non-learners) to tap to an auditory or visual metronome found their movements to be largely reactive, not predictive. Does this reflect the lack of capacity for predictive synchronization in monkeys, or lack of motivation to exhibit this behaviour? To discriminate these possibilities, we trained monkeys to make synchronized eye movements to a visual metronome. We found that monkeys could generate predictive saccades synchronized to periodic visual stimuli when an immediate reward was given for every predictive movement. This behaviour generalized to novel tempi, and the monkeys could maintain the tempo internally. Furthermore, monkeys could flexibly switch from predictive to reactive saccades when a reward was given for each reactive response. In contrast, when humans were asked to make a sequence of reactive saccades to a visual metronome, they often unintentionally generated predictive movements. These results suggest that even vocal non-learners may have the capacity for predictive and tempo-flexible synchronization to a beat, but that only certain vocal learning species are intrinsically motivated to do it.

Predictive rhythmic tapping to isochronous and tempo changing metronomes in the nonhuman primate

“…We found that a rhesus monkey can transfer entrainment in the STF to a novel tempo (in this case 700 ms) without additional training. This is similar to the findings of Takeya et al ., who found that monkeys could generalize the predictive synchronization of eye movements with metronomic visual stimuli to untrained tempi. However, they tested three untrained IOIs, whereas we used only one.…”

“…In fact, the SCT dwell variability increased as a function of the interval following the scalar property of explicit timing observed in many tasks . However, the fact that the macaques’ asynchronies were lagging by 300 ms was interpreted as a sign that monkeys could not predict and instead were reacting to the metronome . The present STF results suggest that monkeys possess strong tapping predictive abilities and can produce NAs when the proper training and task conditions are provided.…”

“…41,42 However, the fact that the macaques' asynchronies were lagging by 300 ms was interpreted as a sign that monkeys could not predict and instead were reacting to the metronome. 12,27 The present STF results suggest that monkeys possess strong tapping predictive abilities and can produce NAs when the proper training and task conditions are provided. Incorporating a perceptual entrainment phase before tapping and a reward contingency for the magnitude of the asynchronies reduced asynchronies by about 50 ms in M01 and 150 ms in M02, compared with asynchronies of about 300 ms observed previously in SCT ( fig.…”

“…It is important to consider that, in the study by Zarco and colleagues, the reward contingencies were focused on the produced interval durations and not on the asynchronies. Indeed, a recent study demonstrated that macaques are capable of predictively synchronizing their eye movements with an isochronous visual beat when the rewards arrived on every predictive synchronized saccade . Nevertheless, macaques are less sensitive than humans in detecting hierarchical metric structures with complex patterns of auditory beats.…”

“…Indeed, a recent study demonstrated that macaques are capable of predictively synchronizing their eye movements with an isochronous visual beat when the rewards arrived on every predictive synchronized saccade. 27 Nevertheless, macaques are less sensitive than humans in detecting hierarchical metric structures with complex patterns of auditory beats. 28,29 Accordingly, the gradual audio-motor evolution (GAE) hypothesis 29 suggests that beat perception and entrainment have emerged gradually in the primate order.…”