In this chapter we establish what it is for something to be implicit or explicit. The approach to implicit knowledge is taken from Dienes and Perner (1999), which relates the implicit-explicit distinction to knowledge representations. What it is for a representation to represent something implicitly or explicitly is defined and those concepts are applied to knowledge. Next we will show how maximally explicit knowledge is naturally associated with consciousness. We argue that each step in a hierarchy of explicitness is related to the unity of consciousness and that fully explicit knowledge should be associated with a sense of being part of a unified consciousness. New evidence indicating the extent of people's implicit or explicit knowledge in an implicit learning paradigm will then be presented. This evidence will indicate people can be consistently correct in dealing with a context-free grammar while lacking any knowledge that they have knowledge. 1.

Linear optic trajectory theory claims that people catch balls by running in a direction that keeps an optic trajectory of the ball linear. The authors show a range of ball trajectories for which departures of the optic trajectory from linearity do not predict which direction people will run, and the direction they choose does not correct these departures. Data from a wide range of ball trajectories show that people run so that the angle of elevation of gaze to the ball increases at a decreasing rate. But it is not yet known why people choose the particular path they do from the many that would achieve this. Thirty years have passed since the pioneering work of Chapman (1968) on how the information obtained from watching a ball that was hit into the air might control a fielder's interception strategy. Although there is general agreement about the control strategy used by fielders when running backward or forward to catch a ball thrown directly toward them, there is no consensus on the strategy used in the more general case in which the fielder must run to the side as well. Considering the ease with which some children learn to catch—just by watching ball flights and trying to catch the

The generalized optic acceleration cancellation (GOAC) theory of catching proposes that the path of a fielder running to catch a ball is determined by the attempt to satisfy 2 independent constraints. The 1st is to keep the angle of elevation of gaze to the ball increasing at a decreasing rate. The 2nd is to control the rate of horizontal rotation necessary to maintain fixation on the ball. Depending on the lateral velocity of the ball relative to the fielder, this rate may be zero or constant at a negative or positive value. The authors show that a simulated fielder implementing the GOAC strategy follows a path indistinguishable from that of real fielders running to catch balls thrown on the same trajectories.