This experiment is a replica of a previous study carried out by Shepard and Cooper (1973). The study aims to look at whether the theory of mental rotation is reliable and valid. Participants were required to look at a number of images, and asked to decide whether the image was a normal or mirror reversed version of specific characters. They were to answer by pressing a button which related to either left or right facing. The time taken to respond was calculated and was theorised that the response time would be greater proportionately to the degree of orientation away from the vertical, or upright, position of the normal character. It was concluded that the response time was in fact greater the further away from the norm the character was presented.
Mental rotation is the ‘imagined turning of a form or shape from one orientation in space to another’ (Colman, 2006. p 453). Mental representations and mental rotation have been part of a psychological debate for a long time. Some psychologist (e. g. Watson, 1913; Pylyshyn, 1973) argue that mental images are not important, and that mental representations are language based and similar to the things they represent.
However another view, put forward by Kosslyn (1980), suggests that mental images are a significant part of mental representations, and that we have the ability to ‘generate a surface representation which is active while we carry out a task’ (Collins et al, 1994). There is further evidence to support this theory. For example, when a person is asked to imagine a dog beside a house, they often know that the size difference between the two objects are of a different size; suggesting that humans do have a ‘bank’ of stored mental images.
Rock (1973) (as cited in Corbalis et al, 1978) states that ‘an observer doesn’t recognise a shape until he or she has assigned a “top” and “bottom axis”, this further helps to understand the significance of mental rotation. As shown by Shepard & Metzler (1971), participants are able to mentally rotate an image, so as to identify if two images are the same or different. In the experiment, participants were shown a series of images.
These images were of two 3-dimensional images, ‘constructed by placing ten cubical blocks face to face’ (Colman, 2006. 453) to form a structure, presented at angles to each other (rotated, but not mirror reversed). Participants were asked to state whether the images were of the same object or whether they were different. They concluded that is was necessary to rotate one of the images, in ones mind, so that one image can mentally be placed over the other to identify a match between the two. The results of this experiment also show that identification became harder the further the orientation from the normal orientation.
The difference in the response time, suggests that participants were mentally rotating the image to come to their decision. The Shepard & Cooper experiment (1973) designed an experiment to test the theory of mental rotation. In the experiment participants were asked to simply name which alphanumerical character was presented to them as quickly as possible, with as few errors as possible. The alphanumeric characters were presented at different degrees of orientation, and were either normal or backwards facing. There were two conditions in the study; Information and no information.
In the information condition all participants were told which character would appear and what degree it would be presented at, the reason for this was that in order to mentally rotate an image, participants needed to know ‘both the identity and angular orientation of each character, for otherwise they could not have known where the upright was’ (Corbalis et al, 1978). In the no information condition, participants were not told which character was to be expected. The results were much the same the Shepard & Metzler experiment, where subjects took longer to identify a character if it was at a greater angular orientation.
This experiment is a direct replica of the ‘no information’ experiment mentioned above. In series of experiments carried out by Corbalis et al (1978), participants were asked to identify which character was presented while it was at different spatial orientations (different angles from the norm). Participants were expected to state whether the character was facing the correct or mirror revered way. Experiment 2 is the closest in relation to our experiment, as each participant was given a different character to identify, and asked to press one button if ‘their’ character appeared and another if any other character appeared.
The character was shown facing both normal and backwards, and results show that participants identified their given character quicker if it was the normal way. However the participant, who was assigned the letter J, was quickest at identifying his character when compared with the other 5 participants. The rest of the participants had a delayed response time when identifying their assigned characters. This suggests that mental rotation was taking place during the response time delay.
All previous studies (Shepard & Metzler, 1971; Shepard & Cooper, 1973; Corbalis et al, 1978) propose that mental rotation takes time to complete. The results from these studies prove that the further the differing orientation from the norm or if a character is mirror reversed, the more time the participants will take to respond. This experiment is aimed to provide further information to mental rotation, and it is proposed that the outcome will be the same as earlier studies, in that the further orientation from the norm, the larger the response time will be.