Infants' Visual Recognition of Pincer Grip Emerges Between 9 and 12 Months of Age

Abstract

The development of the ability to recognize the whole human body shape has long been investigated in infants, while less is known about their ability to recognize the shape of single body parts, and in particular their biomechanical constraints. This study aimed to explore whether 9‐ and 12‐month‐old infants have knowledge of a hand‐grasping movement (i.e., pincer grip), being able to recognize violations of the hand's anatomical constraints during the observation of that movement. Using a preferential looking paradigm, we showed that 12‐month‐olds discriminate between biomechanically possible and impossible pincer grips, preferring the former over the latter (Experiment 1). This capacity begins to emerge by 9 months of age, modulated by infants' own sensorimotor experience with pincer grip (Experiment 2). Our findings indicate that the ability to visually discriminate between pincer grasps differing in their biomechanical properties develops between 9 and 12 months of age, and that experience with self‐produced hand movements might help infants in building a representation of the hand that encompasses knowledge of the physical constraints of this body part.

Infants’ Motor Proficiency and Statistical Learning for Actions

“…This method more closely mirrors how infants’ motor development naturally unfolds ( Ambrosini et al, 2013 ). Infants accumulate both visual and motor experiences with the fine-grained kinematics of an action—such as a certain muscle movement—before piecing together the entire action skill ( Senna et al, 2016 ). Thus, although the whole-hand infants do not yet readily or voluntarily perform a pincer grasp, they may be able to take advantage of finer-grained motor cues for movements that they can do, such as the actor’s hand shape ( Ambrosini et al, 2013 ).…”

Great apes’ understanding of biomechanics: eye-tracking experiments using three-dimensional computer-generated animations

“…When toddlers manipulate objects, they often watch their hands or those of a social partner (Yoshida and Smith 2008). Thus, hands appear to be especially salient for humans (Geangu et al 2015;Longhi et al 2015;Senna et al 2017), and possible vs. impossible hand movements can be discerned at a young age [at 6 but not at 4 months old (Geangu et al 2015); several days after birth (Longhi et al 2015); at 9 months old, but only in those who could perform a pincer grip (Senna et al 2017)]. This discrimination occurred slightly later in Morita et al (2012), who examined reactions to elbow movements [i.e., at 12 but not 9 months old; but for a different result, see Morita et al (2010)].…”

“…Although further research is needed, this possibility is well in line with the overall null results of the present study. Therefore, movies depicting movement of more salient body parts such as the hands (Geangu et al 2015;Longhi et al 2015;Senna et al 2017), or goal-directed actions (Geangu et al 2015;Reid et al 2005), might facilitate research regarding how apes perceive violations of biomechanics.…”

“…Humans appear to be capable of distinguishing biomechanically possible and impossible movements of particular body parts from early ontogeny (Geangu et al 2015;Longhi et al 2015;Morita et al 2010Morita et al , 2012Reid et al 2005Reid et al , 2008Senna et al 2017). To investigate the underlying developmental process, Morita et al (2012) carried out a crosssectional study in which human adults and infants were presented with CG animations of biomechanically possible or impossible elbow movements (i.e., bending upward or downward, respectively), performed by either a human or robot.…”

Action prediction during real‐time parent‐infant interactions

“…Infants become more precise at anticipating an observed action once they have acquired the requisite motor skill (Monroy et al, 2017b;Senna et al, 2016;Stapel et al, 2016), a finding that is not explained by general development. For instance, Monroy et al (2017b) took advantage of the natural variation in the emerging motor skills of young infants to show that those infants who had acquired a specific motor skill (e.g., a pincer grasp) were more precise at anticipating that action than infants of the same age who had not yet mastered that motor skill.…”