g., van der Fits, Otten, Klip, van Eykern, & Hadders-Algra, 1999; Hopkins & Rönnqvist, 2002; Rochat & Goubet, 1995; Rochat, Goubet, & Senders, 1999; Shumway-Cook this website & Woollacott, 2001; Thelen & Spencer, 1998). Infants first begin to develop the motor skills that serve as the foundation for reaching at around 4–5 months of age. These early reaching attempts are characterized by a lack of control in the form of flailing and corrective movements, are often performed with both hands, and are limited to supine or supported
sitting postures because infants cannot yet reach while sitting independently (Corbetta & Snapp-Childs, 2009; von Hofsten, 1991; Thelen et al., 1993; White, Castle, & Held, 1964). New sitters support their weight with their arms, causing them to topple over if they let go to reach for an object (Rochat & Goubet, 1995). In a supine or otherwise supported position, 5-month-olds increase their chances of making contact Small molecule library with an object using a bimanual reach where they approach the object with both hands from either side (Rochat, 1992), but with supplementary postural support to the pelvic girdle and
upper legs or trunk, nonsitters can be induced to carry out more mature reaches, moving just one hand to the object (Hopkins & Rönnqvist, 2002; Marschik et al., 2008). Unimanual reaching increases around 5–6 months of age (Fagard, 1998). Between 6 and 7 months, infants demonstrate two aspects of bimanual role differentiation (e.g., Fagard, Spelke, & von Hofsten, 2009; Kimmerle, Mick, & Michel, 1995). One aspect is related to the characteristics of the target of the reach. For example, infants begin to differentiate between large target objects that require both hands to grasp Ibrutinib molecular weight and small ones that they can obtain with one hand. The second aspect of bimanual role differentiation is related to the functional roles of the two hands. Infants’ reaching and their ability to manipulate objects mature as they use their hands in
complementary roles, such as supporting an object with one hand while manipulating it with the other (Bojczyk & Corbetta, 2004; Fagard, 1998, 2000; Karniol, 1989; Kimmerle et al., 1995; Ramsay & Weber, 1986). At 7 months, infants begin to display stabilized, relatively nonvariable reaching patterns, and show signs of modifying their reaching according to the context (Clearfield & Thelen, 2001). Aside from the direct relationship between the motor control required for infants to stabilize their bodies without support and having their arms free to reach (c.f., Bertenthal & von Hofsten, 1998; Spencer, Vereijken, Diedrich, & Thelen, 2000), other work has demonstrated a relationship between reaching behavior and change in posture that demonstrate an interconnectedness of the motor system (c.f., Babik, 2010; Berger, Friedman, & Polis, 2011; Corbetta & Bojczyk, 2002; Goldfield, 1989; Thurman, Corbetta, & Bril, 2012).