Testing the arousal hypothesis of neonatal imitation in infant rhesus macaques

Abstract

Neonatal imitation is the matching of (often facial) gestures by newborn infants. Some studies suggest that performance of facial gestures is due to general arousal, which may produce false positives on neonatal imitation assessments. Here we examine whether arousal is linked to facial gesturing in newborn infant rhesus macaques (Macaca mulatta). We tested 163 infants in a neonatal imitation paradigm in their first postnatal week and analyzed their lipsmacking gestures (a rapid opening and closing of the mouth), tongue protrusion gestures, and yawn responses (a measure of arousal). Arousal increased during dynamic stimulus presentation compared to the static baseline across all conditions, and arousal was higher in the facial gestures conditions than the nonsocial control condition. However, even after controlling for arousal, we found a condition-specific increase in facial gestures in infants who matched lipsmacking and tongue protrusion gestures. Thus, we found no support for the arousal hypothesis. Consistent with reports in human newborns, imitators’ propensity to match facial gestures is based on abilities that go beyond mere arousal. We discuss optimal testing conditions to minimize potentially confounding effects of arousal on measurements of neonatal imitation.

Neonatal imitation in context: Sensorimotor development in the perinatal period

“…Keven & Akins (K&A) propose that spontaneous aerodigestive behaviours may be mistaken for neonatal imitation; however, well-designed neonatal imitation studies already account for reflexive and arousal-driven responses (for a review, see Simpson et al 2014a). When measuring arousal, either physiologically or behaviourally, and examining its relationship to imitative responding, evidence shows that for humans (e.g., Nagy et al 2013) and nonhuman primates (NHP; e.g., Paukner et al 2017;Simpson et al 2014b), changes in arousal alone cannot account for neonatal imitation. In addition, K&A acknowledge that they "have not explained, so far, the differential responses of neonates to specific gestures" (sect.…”

What happened to mirror neurons?

“…claimed to provide evidence of imitation in newborn monkeys (Ferrari, Visalberghi, Paukner, Fogassi, Ruggiero & Suomi, 2006;Ferrari, Paukner, Ruggiero, Darcey, Unbehagen & Suomi, 2009;Paukner, Ferrari & Suomi, 2011;Simpson, Paukner, Sclafani, Suomi & Ferrari, 2013;Paukner, Simpson, Ferrari, Mrozek & Suomi, 2014;Simpson, Miller, Ferrari, Suomi & Paukner, 2016;Kaburu, Paukner, Simpson, Suomi & Ferrari, 2016;Paukner, Pedersen & Simpson, 2017;Wooddell, Simpson, Murphy, Dettmer, Paukner, 2019). These studies did not use the "crosstarget" procedure which has been agreed, by both enthusiasts and sceptics, to be necessary to detect imitation in newborns (e.g.…”

Re-analysis of data reveals no evidence for neonatal imitation in rhesus macaques

“…Beforehand, I had pre-registered my intended statistical analyses for each separate dataset on the Open Science Framework (https:// osf.io/uksv9/). Yet, one of the authors kindly pointed me to the full dataset (N = 163)-published as electronic supplementary material for Paukner et al [30]-and informed me that 'All other studies used subsets of these infants'. I therefore deviated from my pre-registered analysis plan and instead analysed all data from the full sample together.…”

“…In a field ripe with controversies, however, one of the most intriguing pieces of the puzzle is the large number of publications on neonatal imitation in rhesus macaques. Since 2006, a total of 10 studies from a single research group have claimed to provide evidence for the existence and function of neonatal imitation in this species [22][23][24][25][26][27][28][29][30][31]. Here I reassess the empirical basis for these claims.…”