It's a Jungle in There: How Competition and Cooperation in the Brain Shape the Mind by David A. Rosenbaum Page A

mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought. Focalization, concentration, of consciousness are of its essence. It implies withdrawal from some things in order to deal effectively with others.” 9 This definition does not restrict the effects of attention to the overt performance of selected acts but points, instead, to a more subtle, inner selectivity. Can this more subtle view be explored scientifically? To the extent that it highlights internal rather than only external experience, does this vitiate an action-centered view?

    FIGURE 3. The Rubin figure.
    Consider an image that can be seen in one way or another, the so-called Rubin figure ( Figure 3 ), named for the Danish psychologist, Edgar Rubin, who introduced it in 1915. 10 The Rubin figure can be seen either as a wine goblet or as two faces looking at each other. The most interesting feature of the figure is that you can see it in either of these ways, but not as both of them at once. The two perceptions flip back and forth. No matter how hard you try, you can’t see both of them simultaneously.
    When I show the Rubin figure to students in my class, I ask them to raise their hands when they see a goblet and to lower their hands when they see the faces. For the students who are willing to participate in this exercise, their hands go up or down once every few seconds. 11
    A similar outcome is obtained with another reversible figure, the Necker cube ( Figure 4 ), named after Louis Albert Necker, a Swiss crystallographer who first published an image of his famous cube in 1832. 12 The Necker cube is a two-dimensional rendering of a 3D wire-frame box. Because the 2D depiction is visually impoverished, lacking cues about the figure’s 3D orientation, it tends to be seen with one side close to the observer and the other side far from the observer. The two interpretations switch back and forth. The side that seems farther away suddenly jumps to the front, or vice versa. The flipping occurs again and again, as if of its own accord. Students who raise and lower their hands to show which side seems frontward change their hand positions at about the same rate as when they indicate their perceptual switches while viewing the Rubin figure.

    FIGURE 4. The Necker cube.
    What accounts for this perceptual vacillation, and why am I speaking of it here in this discussion of attention? One reason is that perceptual instability suggests inner conflict. Two inner factions seem to duke it out. One wants one side of the Necker cube to be close; the other wants that side to be far. Each fights so hard for its point of view that your perception—your response to the image—gets jostled back and forth.
    The other reason I’m speaking about the Necker cube is that the perceptual reversal of this stimulus also points to the importance of action selection. Seeing the Necker cube one way or the other is an action, albeit of an elementary kind. The action can take the form or lowering or raising your hand, or it can take the form of verbally reporting the position of a vertex of the cube: “Now it’s in front. Now it’s in back.” A reason for the vacillation may be that attention is not just for deciding how to interpret things but also for deciding what to do physically in relation to them. In the case of the Necker cube, it may be that you can see only one side of the cube as the front and one side as the back because if you were you to reach out and grab the cube in 3D, you’d be unable to grab one side in a near place and in a far place simultaneously. If you put your fingers around the back edge, your hand would be in the back, not in the front, and if you were to put your fingers around the front edge, your hand would be in the front, not in the back. Which edge is in the front or in the back is perceptually ambiguous in the 2D image, but the need to commit to a front reading or a back reading is
required
for the