Ontogeny of tool use: how do toddlers use hammers?

Abstract

Hammering with a hand tool appears early in life. Skillful hammering involves accommodating movements to properties of the hammer, orienting the hammer's head to the item to be struck, and maintaining stable posture during forceful action with the arm(s). We aimed to characterize development of these abilities in young children (12, 18, and 24 months old). Children struck at a peg with a hammer held in the hand or a hammer attached to a handle. Children struck more frequently with a hard hammer surface than a soft one, and more frequently (although less accurately) with handled hammers than with non-handled hammers. Developmental differences were evident in accuracy, number of strikes, and kinematic parameters, especially with the handled object. Children's ability to use objects for forceful and accurate percussion changed measurably over the second year, in tandem with improving postural stability and greater motion of the elbow.

The Development of Bimanual Coordination Across Toddlerhood

“…Ramsay () documented fluctuating periods of midline oscillatory block‐banging in infants starting at about 5 or 6 months. Fragaszy, Simpson, Cummins‐Sebree, and Brakke () and Kahrs et al () assessed changes in hammering movements between 12–24 and 19–35 months of age, respectively. In both of these studies, children of all ages readily engaged in the continuous rhythmic activity required for hammering and demonstrated improvements in efficiency and accuracy across months following changes, typically proximal to distal, in the arm joints responsible for the movement.…”

“…In studies using similar tasks (i.e., banging) with children in the same age range, toddlers have evidenced developmental changes in whether the shoulder, elbow, or wrist joint is generally used, changes that follow a proximal‐to‐distal sequence (Fragaszy et al, ; Kahrs et al, ). This sequence is commonly reported in the literature of motor development (see Newell & van Emmerik, , for a discussion of sequential trends).…”

“…Following others’ perspectives on sequential changes in recruitment of degrees of freedom (see, as a brief review, Newell & van Emmerik, ) and armed with evidence that the period of observation had the potential to demonstrate changes in the primary joints employed for the task (e.g., Fragaszy et al, ; Kahrs et al, ), we hypothesized that toddlers would explore at the joint level of analysis to improve their anti‐phase coordination pattern performance. This hypothesis arose from a possible mechanical interference between limbs when the shoulders (and thus large masses) were the primary joints that were moving (see Chapter IX for consideration of other explanations).…”

“…It is also possible that a decrease in oscillation frequency helps toddlers maintain the anti‐phase coordination pattern in terms of the mechanics of the movement. As stated in Chapter II, at younger ages toddlers primarily use the shoulder to perform oscillatory motions in related task contexts (Fragaszy et al, ; Kahrs et al, ). As argued in Chapters III and IX, this would reciprocally influence motions at the trunk that might interfere with the oscillation of the other arm.…”

The neurological phenotype of developmental motor patterns during early childhood

“…In children of six months and older, the process of synaptic organization continues to peak until the second year of life (Chugani, 1998;Ismail et al, 2017). During this period, the child achieves and subsequently refines voluntary functional motor performances, such as reaching, grasping, manipulation, sitting, standing, and walking (Fragaszy, Simpson, Cummins-Sebree, & Brakke, 2016;Hempel, 1993aHempel, , 1993bYang, Mitton, Musselman, Patrick, & Tajino, 2015).…”