G Rounding N Aïve P Hysics and O Ptics in P Erception

Many adults hold mistaken beliefs concerning the behavior of mechanical motion and reflections. In the field of psychology this has been investigated in the areas of naïve physics and naïve optics. The interesting question regards where these false beliefs come from. Particularly thought-provoking is the case of errors which are at odds not only with (presumably or even actually) known physical/optical concepts, but also with what people would actually perceive. Some errors are in fact consistent with what people see in ecological conditions while others apparently are not. This has led to the former being referred to as perceptual errors and the latter as conceptual errors (Lawson & Bertamini 2006). We propose that many of these ‘conceptual errors’ are generalizations of what can be actually perceived under some conditions that are then incorrectly applied under others. In this sense, they can be thought of as a second way in which perception shapes naïve beliefs. Grounding Naïve Physics 2 1. ERRONEOUS BELIEFS IN NAÏVE PHYSICS AND OPTICS In psychology there has been a great deal of research on the naïve beliefs that people hold about motion as studied in traditional mechanics. This research covers a number of areas: the trajectory and speed of falling objects (Bozzi 1959; Kaiser et al. 1985; McCloskey et al. 1983; Runeson 1974; Shanon 1976) and thrown objects (Hecht & Bertamini 2000; McCloskey et al. 1980; Shaffer & McBeath 2005); the dynamics of pendulum oscillations (Bozzi 1958; Frick et al. 2005; Jansson & Runeson 1969; Pittenger 1990), objects in rotation (Proffitt & Gilden 1989; Proffitt et al. 1990) and objects released after being rotated (McCloskey 1983a; McCloskey et al. 1980). This field of studies has been called naïve or intuitive physics. More recently a similar area of study has investigated naïve beliefs concerning the behavior of mirror reflections: naïve optics (e.g. Bertamini et al. 2003; Bertamini et al. 2010; Bianchi & Savardi 2012; Croucher et al. 2002; Savardi et al. 2010). Both areas of research have revealed that people hold a surprising number of erroneous beliefs. For example McCloskey et al. (1980) used simple paper-and-pencil tasks to show that despite the fact that many people study physics at school, they still expect a ball exiting from a curved tube (Fig. 1a) or flying from a sling (Fig. 1b) to continue along a curved trajectory rather than move straight along a tangent. They also believe that a ball carried by a horizontally moving object and then dropped will fall straight down or even in the opposite direction, i.e. backwards (Fig. 1c). Moving to naïve optics, many people expect that a person entering a room and making a parallel approach to a plane mirror will start to see their reflection at the nearer edge before they actually do see it (Fig. 2a) or that they will see it appearing at the mirror’s farther edge rather than the nearer edge (Fig. 2b) (Croucher et al. 2002). Moreover, a significant percentage of adults don’t expect the reflection of objects moving at various angles with respect to a mirror to follow symmetrical patterns, but to move along the same line either in the same allocentric direction (which means that if the object is moving towards the mirror surface, in the reflection it will move away from it — Fig. 2c) or in the opposite direction but still along the same line (Fig. 2d) (Savardi et al. 2010). Vol. 9: Perception and Concepts 3 Ivana Bianchi & Ugo Savardi Figure 1: Many people expect the dashed trajectories represented in the figure rather than the correct continuous ones. McCloskey’s tasks: 1a) C-tube problem: draw the path that the ball will follow on emerging from a curved tube if it is inserted into one end of the tube and then shot out of the other end; 1b) Sling problem: a ball attached to a string is twirled at high speed in a circle above a person’s head — draw the path that the ball will follow after the string breaks (assume it breaks when the ball is at the point shown in the diagram); 1c) Airplane problem: an airplane is flying at a constant speed and altitude — draw the path that a ball dropped from the plane will follow until it hits