experimental

Information Sheet on Mental Rotation Experiment

There are two goals with this experiment:

1. Learn about the concept of mental rotation of visual images

2. Create a new experiment based on a review of the literature related to an old experiment

3. Write a complete lab report, including Abstract

Background

Shepard & Metzler (1971) introduced the use of mental rotation of visual objects. Their paradigm consisted of a pair of stimuli that were either (a) identical save for rotation or (b) identical save for rotation and a mirror-image reversal (Reflected). They hypothesized that in order for observers to distinguish between possibilities (a) and (b), they would have to mentally rotate one of the objects until it appeared to be the same orientation as the other. At this point, they could then make a direct comparison of the two objects. If they were now identical, they concluded that condition (a) held. If they were still different, then condition (b) must hold. They further hypothesized reasoned that mental rotation was analogous to real physical rotation of the actual objects represented by the pictures. For real objects the amount of time to rotate them should be proportional to the number of degrees of rotation and the same should be true for mental rotation. Thus the major prediction of the experiment was that the relationship between reaction time (RT) and degrees should be linear. As can be seen in the following graph, their prediction was upheld.

Figure 1: Adapted from Shepard & Metzler (1971)

Interestingly, Shepard & Metzler used fairly complex three-dimensional-like drawings of attached cubes:

Figure 2: from Shepard & Metzler (1971)

Many subsequent studies have achieved similar results using simpler two-dimensional figures (e.g. Cooper, 1975):

Figure 3: from Cooper (1975)

Most experimental psychology courses place heavy emphasis on replicating classic experiments, and we have certainly been doing that in this course as well. However, science obviously does not progress by replication alone. Some studies involve completely novel ideas that turn out to yield interesting results. Among these are the ones that have become the classic experiments. Sperling’s (1960) Iconic imagery, Sternberg’s (1969) scanning of short-term memory and Shepard & Metzler’s (1971) study of mental imagery certainly fall into this category. However, most studies are not completely novel; rather they are variations on an original experiment. While not as earth-breaking, these studies perform the valuable function of validating and fleshing out the classic experiments, so that we learn more about their true implications. In this case, instead of replicating the classic experiment, there is one central issue I would like us to examine.

The importance of this experiment is that by showing that “mental” rotation is analogous to physical rotation in that both are (more-or-less) linear with degrees of rotation, one can infer mental processes by virtue of doing psychology experiments. Back when Behaviorism held sway, this was a major counter-point. Cognitive psychology is now well-established, but I have always elt that the central idea of this experiment is a bit shaky. First of all, there is the point that linearity is far from perfect. Second, the evidence for mental rotation is indirect even if linearity is maintained. So, my idea is to measure the concept more directly.

If we are literally mentally rotating forms, then we should have “seen” forms at angles that were not actually presented, but that we rotated through. So, the current experiment will have two different training sessions: (1) uses forms that are rotated +80 degrees (Clockwise) or (2) uses forms that are rotated -80 degrees (Counter-Clockwise). Everyone then is tested using the same forms (+40 degrees of rotation and -40 degrees. The idea is that even though no P literally saw either +40o or 40o, the ones who trained with +80o will have “mentally seen” +40o and the ones who trained with 80o will have “mentally seen” -40o.

It will use forms like the following