"They allow actors not only to decide whether they want to use an object, but also how to utilize the object'" #readingToday 

For every object, humans learn not only what goals they can, in principle, achieve with it ("function knowledge"), but also the motor behaviors that are required to achieve these goals ("manipulation knowledge") (Kelemen, 1999; Buxbaum et al., 2000; Buxbaum and Saffran, 2002; Casby, 2003, for a review, see van Elk et al., 2013). When growing up, one learns, for example, that a tap is for getting water, and that this requires turning it clockwise. Similarly, one learns that a knife is for cutting, and that this requires alternating forward and backwards movements, with an amount of downward pressure that depends on the object one wants to cut. Objects, therefore, seem to provide one with the same links between potential action outcomes and required motor behaviors that are central to the control of voluntary action (see Hommel et al., 2001). These links allow objects to act as an interface between an actor's goals and their motor system (cf. van Elk et al., 2013). They allow actors not only to decide whether they want to use an object (by matching object functions to one's current goals), but also—if they do—to derive how to utilize the object to achieve the desired result (by using manipulation knowledge to guide one's motor behaviors with the object).

The affordance-matching hypothesis: how objects guide action understanding and prediction