64 • CHAPTER 3 Perception
but a pattern like the circles that are light on the bottom would be created by an indenta-
tion in a surface (see Figure 3.25c). The assumption that light is coming from above has
been called the light-from-above heuristic (Kleffner & Ramachandran, 1992). Apparently,
people make the light-from-above assumption because most light in our environment
comes from above. This is true of the sun, as well as most artifi cial light sources.
Another example of the light-from-above heuristic at work is provided by the two
pictures in ● Figure 3.26. Figure 3.26a shows indentations created by people walking
in the sand. But when we turn this picture upside down, as shown in Figure 3.26b, the
indentations in the sand become rounded mounds.
Thus, one reason we are able to perceive and recognize objects and scenes is because
of our knowledge of physical characteristics of our environment. We also have knowl-
edge about regularities of the environment that indicate what types of objects typically
occur in specifi c types of scenes.Semantic Regularities In language, semantics refers to the meanings of words or
sentences. Applied to perceiving scenes, semantics refers to the meaning of a scene. This● FIGURE 3.26 Why does (a) look like indentations in the sand and (b) look like mounds
of sand? Note that these are the same images, but (b) is upside down.Bruce Goldstein
(a)(b)● FIGURE 3.25 a) Some of these discs are perceived as jutting out, and some are perceived
as indentations. The explanation for this perception is that light coming from above will
illuminate (b) the top of a shape that is jutting out and (c) the bottom of an indentation.Front
viewSide
viewLight Light(a) (b) (c)Copyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.