Mental rotation is somewhat localized to the right cerebral hemisphere. It is thought to take place largely in the same areas as perception. It is associated with the rate of spatial processing and intelligence (Johnson 1990, Jones 1982, Hertzog 1991). Mental rotation is the brain moving objects in order to understand what they are and where they belong. It has been studied to try to figure out how the mind recognizes objects in the environment. Researchers call these objects stimuli. A stimulus then would be any object or image seen in the person’s environment that has been altered in some way. Mental rotation then takes place for the person to figure out what the altered object is.
Mental rotation can be separated into the following cognitive stages (Johnson 1990):
- Create a mental image of an object
- Rotate the object mentally until a comparison can be made
- Make the comparison
- Decide if the objects are the same or not
- Report the decision
How mental rotation ability is assessed 
In a mental rotation test, the subject is asked to compare two 3D objects (or letters) and state if they are the same image or if they are mirror images (enantiomorphs). Commonly, the test will have pairs of images each rotated a specific amount of degrees (e.g. 0°, 60°, 120° or 180°). Some pairs will be the same image rotated, and others will be mirrored. The subject will be shown a set number of the pairs. The subject will be judged on how accurately and rapidly they can distinguish between the mirrored and non-mirrored pairs.
Notable research 
Roger Shepard and Jacqueline Metzler (1971) originally discovered this phenomenon. Their research showed that the reaction time for participants to decide if the pair of items matched or not was linearly proportional to the angle of rotation from the original position. That is, the more an object has been rotated from the original, the longer it takes an individual to determine if the 2 images are of the same object or enantiomorphs (Sternberg 247). Shortly afterwards, Robert Sekuler and David Nash (1972) demonstrated that a pair of mental transformations, size scaling and rotation, could be carried out in parallel.
In further research, Shepard and Cooper (1982) have proposed the concept of a "Mental Imagery" facility, which is responsible for the ability to mentally rotate visual forms. Additionally, it has been found it does not matter on which axis an object is rotated, but rather the degree to which it is rotated that has the most significant effect on response time. So rotations within the depth plane (i.e., 2D rotations) and rotations in depth (3D rotations) behave similarly. Thus, the matching requires more time as the amount of depth rotation increases, just as for within the depth plane.
In subsequent research, it has been found that response times increase for degraded stimuli and can decrease when participants are allowed to practice mentally rotating imagery (Sternberg 247). This research has been instrumental in showing how people use mental representations to navigate their environments.
Also, males tend to be slightly faster in mental rotation tasks than females. The ability to rotate mentally (measured in terms of decline in response time) peaks in young adult-hood, and declines thereafter.
Recent breakthroughs in nuclear magnetic resonance have allowed psychologists to discover what parts of the brain correspond to the use of this mental imagery function. Using Functional Magnetic Resonance Imaging, psychologists have shown that when participants are performing mental rotation tasks, there is activation in Brodmann's areas 7A and 7B, the middle frontal gyrus, extra-striate cortex, the hand somastosensory cortex, and frontal cortex (Cohen et al.).
Other recent research has centered on whether there might be multiple neural systems for the rotation of mental imagery. Parsons (1987) found that when participants were presented with line drawings of hands rather than Shepard and Metzler-like 3D blocks showed embodiment effects in which participants were slower to rotate hand stimuli in directions that were incompatible with the way human wrist and arm joints move. This finding suggested that the rotation of mental imagery was underlain by multiple neural systems: that is, (at least) a motoric/tactile one as well as a visual one. In a similar vein Amorim, Isableu and Jarraya (2006) have found that adding a cylindric "head" to Shepard and Metzler line drawings of 3D objects can create facilitation and inhibition effects as compared to standard Metzler-like stimuli, further suggesting that these neural systems rely on embodied cognition.
Studies of the development of mental rotation have revealed the emergence of this ability in male infants by 5 months of age (Moore & Johnson, 2008).
Shepard and Metzler in depth 
In 1971, Roger N. Shepard and Jacqueline Metzler conducted the most famous study done on mental rotation. They were the first to introduce this idea to cognitive science. Their experiment specifically tested mental rotation on three-dimensional objects. Each subject was presented with multiple pairs of three-dimensional, asymmetrical lined or cubed objects. The experiment was designed to measure how long it would take each subject to determine whether the pair of objects were indeed the same object or two different objects. For each pair, the subject was asked to pull a right-handed lever if the two objects were congruent with respect to a three-dimensional shape and to pull a left-handed lever if the objects were not. Shepard’s hypothesis was that this task would be done by creating a mental three-dimensional image of the first depict object and mentally rotating that object to see if it matches its pair. The results of the experiment confirmed the original hypothesis. The time it took for each subject to identify if two objects were identical was directly proportional to the angular rotational difference between them. The greater the angular rotational difference, the greater the time it took to identify the similarity (Shepard & Metzler, 1971).
Vandenburg and Kuse 
Steven G. Vandenberg and Allan R. Kuse conducted a similar experiment in 1978 that was based on Shepard and Metzler’s original study. This test was constructed using India ink drawings. Each stimulus was a two-dimensional image of a three-dimensional object drawn by a computer. The image was then displayed on an oscilloscope. Each image was then shown at different orientations rotated around the vertical axis. Following the basic ideas of Shepard and Metzler’s experiment, this study found a significant difference in the mental rotation scores between both the two sexes. Correlations with other measures showed strong association with tests of spatial visualization and no association with verbal ability (Kuse & Vandenberg 1978).
Mental rotation and the brain 
In 1999, a study done by seven scientists was conducted to find out which part of the brain is activated during mental rotation. Seven volunteers between the ages of twenty-nine to sixty-six participated in this experiment. None of the volunteers had a history of neurological illness. A PET scan was used to record the brain activity. Each subject was presented with eight characters during each scan, twice in its normal position and twice reversed. Scanning was conducted with the lights dimmed and the noise level low. After being placed in the scanner, each subject received both oral and written instructions and was given thirty-two practice trials. Each trial started with showing the subjects a black screen for two seconds, followed by thirty-two stimuli presented at a rate of two seconds each. The subject had those two seconds to respond to each stimuli or else the image would immediately switch to the next. If they did respond, the screen went black until the end of the two-second interval. With each stimulus presented, the subject had one of two buttons to push: one if the image shown was normal and one if the image was mirror-reversed. rCBF was measured in the brain by recording the distribution of the cerebral radioactivity following an injection of H215O into a small vein in each of the subject’s left forearm. The only area of the brain in which the rCBF levels changed and that was found directly correlated with the mental rotation tasks was in the right posterior parietal lobe, specifically surrounded around the intraparietal sulcus. A small area of activation was also recorded in the left parahippocampal gyrus. The results this study collected are evidence that the task of mental rotation recruits visual-spatial changes that are implemented in this brain region (Irnia, Egan, 1999).
Mental rotation and color 
Physical objects that we imagine rotating in everyday life have many properties such as textures, shapes, and colors. A study at the University of California Santa Barbara was conducted to specifically test the extent to which visual information, such as color, is represented during mental rotation. This study used several methods such as reaction time studies, verbal protocol analysis, and eye tracking. In the initial reaction time experiments, those with poor rotational ability were affected by the colors of the image, whereas those with good rotational ability were not. Overall, those with poor ability were faster and more accurate identifying images that were consistently colored. The verbal protocol analysis showed that the subjects with low spatial ability mentioned color in their mental rotation tasks more often than participants with high spatial ability. One thing that can be shown through this experiment is that those with higher rotational ability will be less likely to represent color in their mental rotation. Poor rotators will be more likely to represent color in their mental rotation using piecemeal strategies (Khooshabeh, & Hegarty).
Mental rotation on athleticism and artistic ability 
Research on how athleticism and artistic ability affect mental rotation has also been done. Pietsch, S., & Jansen, P. (2012) showed that people who were athletes or musicians had faster reaction times than people who were not. They tested this by splitting people from the age of 18 and higher into three groups. Group 1 was students who were studying math, sports students and education students. It was found that through the mental rotation test students who were focused on sports did much better than those who were math or education majors Also it was found that the male athletes in the experiment were faster than females, but male and female musicians had no significant reaction time change.
Moreau, D., Clerc, et al. (2012) also investigated if athletes were more spatially aware than non-athletes. This experiment took undergraduate college students and tested them with the mental rotation test before any sport training, and then again afterward. The participants were trained in two different sports to see if this would help their spatial awareness. It was found that the participants did better on the mental rotation test after they had trained in the sports, than they did before the training. There are ways to train your spatial awareness. This experiment brought to the research that if people could find ways to train their mental rotation skills they could perform better in high context activities with greater ease.
Real Life Application 
As shown in the studies athletes are more spatially aware because their training makes them have to be. Dancers are also very spatially aware, due to the immense amount of training and practice of turns and mental rehearsal. The more musical or athletic a person is, the more they are spatially aware and can rotate images in the environment. The use of mental rotation can be strengthened by becoming trained in a certain art or sport. Without mental rotation people would not be able to process information as quickly and accurately.
Future Research 
All the research that has been done on mental rotation has been based on how fast different people rotate images and objects and if certain types of people are faster or slower. Further research could be done to see what mental rotation actually does for a person’s perception and learning. It could be used to see how different types of people learn and how developing these skills could make them learn more accurately.
Also based on the research previously done, looking into how males and females mentally rotate objects could be looked into with more detail. Also age would be a factor to look into because in other fields age has been shown to change the way people perceive images and objects in their environment. If people can learn how they perceive them than biases could be figured out and people could learn how to control what they perceive and how they view the world they can learn how they can change opinions.
See also 
- Mental rotation lesson using PsyToolkit (with Java demonstration)
- Mental rotation training/testing flash application
- Amorim, Michel-Ange, Brice Isableu and Mohammed Jarraya (2006) Embodied Spatial Transformations: “Body Analogy” for the Mental Rotation. Journal of Experimental Psychology: General.
- Cohen, M. "Changes in Cortical Activities During Mental Rotation: A mapping study using functional magnetic resonance imaging" 1996 February 12, 2006 http://airto.bmap.ucla.edu/BMCweb/BMC_BIOS/MarkCohen/Papers/Rotate.pdf
- Hertzog C., and Rypma B. (1991). Age differences in components of mental rotation task performance. Bulletin of the Psychonomic Society, 29(3), 209-212.
- Johnson A.M. (1990). Speed of mental rotation as a function of problem solving strategies. Perceptual and Motor Skills, 71, 803-806.
- Jones B., and Anuza T. (1982). Effects of sex, handeness, stimulus and visual field on "mental rotation". Cortex, 18, 501-514.
- Mental Rotation Experiment. Feb 20, 2006. <http://psychexps.olemiss.edu/InstrOnly_Page/mentalrotation.htm>
- Moore, D. S. and Johnson, S. P. (2008). Mental rotation in human infants: A sex difference. Psychological Science, 19, 1063-1066.
- Moreau, D., Mansy-Dannay, A., Clerc, J., & Guerrién, A. (2011). Spatial ability and motor performance: Assessing mental rotation processes in elite and novice athletes. International Journal Of Sport Psychology, 42(6), 525-547.* Parsons, Lawrence M. (1987) Imagined spatial transformations of one’s hands and feet. Cognitive Psychology 19: 178-241.
- Pietsch, S., & Jansen, P. (2012). Different mental rotation performance in students of music, sport and education. Learning And Individual Differences,22(1), 159-163. doi:10.1016/j.lindif.2011.11.012* Rohrer, T. (2006). The Body in Space: Dimensions of embodiment. In Body, Language and Mind, vol. 2. Zlatev, Jordan; Ziemke, Tom; Frank, Roz; Dirven, René (eds.). Berlin: Mouton de Gruyter, forthcoming 2006.
- Sekuler, R and Nash, D. "Speed of size scaling in human vision." Psychonomic Science 1972, 27(2), 93-94.
- Shepard, R and Cooper, L. "Mental images and their transformations." Cambridge, MA: MIT Press, 1982.
- Shepard, R and Metzler. J. "Mental rotation of three dimensional objects." Science 1971. 171(972):701-3.
- Sternberg, R.J. (2006).Cognitive Psychology 4th Edition. Belmont, CA: Thomson
- Yule, Peter. "A new spin on mental rotation." 1997 University of London. February 12, 2006 <http://www.psyc.bbk.ac.uk/people/associates/pgy/notes/rotation/>.