The Nature Of Mental Imagery

Imagery was excluded from the psychology study because of the influence of the behaviorism. As the flourishing of Cognitive Psychology, in recent years, the idea began to have a high degree of attention by psychologists again. There is always non-stop controversy in the imagery study, current controversy is focused on whether visual mental imagery is really visual or dominated by general-purposed cognitive process. According to the standpoint of superficial nature, imagery theory can be roughly divided into two schools. The representatives as Kosslyn(1981,2003a) consider imagery a unique references' representation as perception, different from proposition representation, it is simulated imagery, which has its own function and role in psychological activities, visual imagery can cause the activation of visual presentation from top to bottom, that was named picture theory by Pylyshyn (2002, 2003); The representatives as Pylyshyn (1981,2003) noted that as imagery has no independent status and function, it can not used to explain psychological phenomenon, information was presented as proposition. Although there is subjective image experience in imagery, it is only incidental phenomenon, like the heat emanated by bulb unrelated to the reading process when we read. Kosslyn(2003b) called it Nihilistic Hypothesis. The bone of contention mainly focused in the following three aspects: whether presentation form of imagery is simulated presentation or proposition presentation; whether the reason of similarity of imagery and perception is the tacit knowledge people has, but not the simulated presentation form of imagery; whether the discovery of neuropsychology helps the solve of the controversy.Based on the above analysis, new experiment paradigm and event-related potentials(ERP) were used to seek out the presentation form, function and the relationship to proposition presentation of imagery presentation. As follows: The experiment altogether sets up two tasks: normal-mirror image task and alphanumeric judgment task. We asked subjects to judge the letters or numbers appear on the screen if they are normal or mirror image in normal-mirror image task, and judge the stimulate on the screen letters or numbers in the alphanumeric judgment as fast and accurate as possible. The result shows that in the normal-mirror task, the mental rotation effect that reaction time increases as the rotation angel increases appears, but in the alphanumeric judgment task, reaction time doesn't increase as the rotation angel increases. Further research on the reaction time shows that the trend that reaction time changes as the angel changes is different in the condition of normal and mirror image, and there are step phenomenon in both cases which can not be perfectly explained in both the visual theory and null hypothesis, so the theoretical hypothesis that imagery representation and proposition coexist, they can access and transform each other and may participate in a joint experiment proposed.Imagery presentation form is the center of the two theories, and is also the core of this research, but due to the more or less shortcomings exit in the evidence give support to the existence of imagery and representation, the foundation of this study is the existence and uniqueness of imagery and presentation. We use relatively new experiment paradigm in the experiment 2 A and B, so as to exclude non-interference variables that may interfere the existence and the reliability of evidence of the imagery and presentation as much as possible. Experiment 2 A and B allow the subjects to judge the consistence of the two graphics appear before and after or the graphics represented by Chinese characters. The result shows that the right judgment reaction time changes as the difference size of the graphics given before and after the change, and it is influenced by time factor, but the reaction time doesn't change as the differences of the graphics presented by the letters, and also isn't influenced by time factor. Thereby, it indicts the differences between imagery presentation and proposition presentation, and imagery presentation has its own unique function.Experiment 2 A and B indicate that there is an imagery presentation method, image size and time interval have an impact on the reaction of subjects. But the result of experiment 1 shows that there is no significant main effect in the alphanumeric judgment task, that reaction time doesn't increase as the rotation angel increases, which means that the judgment was not carried through after the rotation to a specific location in the alphanumeric judgment task.. In the classic psychological scanning experiments, Kosslyn(1973,1978) found distance effect, but Pylyshyn didn't(Pyhyshyn,1981). In the studies of size effect, which means the small object can not be easy to see compared to those big ones, so does it in imagery. Kosslyn (1974,1975,1980) found that when asked the subjects to form visual imagery, the time we affirmed if the object had a certain feature was affected by the size of image, but if we didn't ask them to do this, reaction time was not restricted by the object size, but associated with the frequency of the object's characteristics. It also shows that the use of image is conditional, based on the nature and requirement of the tasks. Experiment 3 asks subjects to judge if the shapes of two graphics appear before and after are the same, it is found that reaction time no longer changes as the difference size of the graphics change, so as to demonstrate that when the subjects make judgment of the consistence of the shape, they don't zoom them to the same size before the comparison, this may indicate that the use of imagery is conditional, but not widespread.Supporters of hypothesis assume that the reason why imagery seems like perception and is the simulated imagery is that people have mastered the tacit knowledge used to imaging (Pylyshyn,2003), Pylyshyn indicated that there is a common problem in nearly all of the studies that support visual theory, that is when asked the subjects to imagine something, they always asked themselves how it would be when saw it at first, than they would imitate the response, in this case, there is relation between perception and imagery. Therefore, Pylyshyn named this null hypothesis, for it doesn't make assumptions towards the representation form of imagery, but the tacit knowledge and some basic psychological skills make effects, he even said that though imagery presentation has similarity to perception presentation, it doesn't mean that the presentation form of imagery is similar to pictures, because the representation form of imagery is not necessarily similar to the form of pictures. Experiment 4 compared psychological scanning task to visual scanning task, it shows that: there is only distance effect but not left and right visual effect in psychological scanning task, and still no interaction, which indicted that psychological scanning seems to be the self-terminating scanning model diffused from middle to both sides, but not full-scanning. And visual scanning task only has distance and visual main effects without interaction, which indicates that visual scanning also begins from middle, but has a priority at left. Although psychological scanning and visual scanning both begin from middle, they have totally different model: psychological scanning seems to diffuse from middle to both sides, with more parallel processing, but visual scanning seems to diffuse from left to right, with more serial processing. Therefore, the result may be that distance effect in psychological scanning is not caused by the imitation of perception or the tacit knowledge, at least it is not the full-imitation of visual scanning.Based on the above behavioral experiments, we use behavioral experiment in experiment 5 A and ERP in 5 B to seek out the relationship between imagery presentation and proposition presentation and the corresponding neuropsychological basis. Experiment 5 asked the subjects to judge if the pictures or characters appear on the screen if they are the same thing, result shows that when the first project matches the end project (both of the simulations before and after are pictures or characters), subjects have the short reaction time, but when they are not matched(one stimulation is picture and the other is character), the reaction time is long. The result once again indicates that these two forms of presentation is different, demonstrated that when subjects make consistence judgment, they transform the presentation form of end project to the first project before making the judgment. But in the condition when the first project is characters and the end project is pictures , the reaction time is faster when the end project is also characters , along with that the transformation speed of imagery presentation is faster than that of proposition presentation, the reason may be that imagery presentation can stimulate proposition presentation automatically, the transformation is self-moving processing and independent from will, but it is not self-motive but controlled processing and will needs when the proposition presentation transforms into imagery presentation.From the experiments above, the following conclusions are put forward: imagery presentation a unique simulated presentation that is different from proposition presentation , they are separated both in behavioral and neuropsychological basis; the psychological operation in imagery tasks are not the simulation of perception, the hypothesis of tacit knowledge can not explain the results this study; the use of imagery is conditional, but not widespread; imagery presentation and proposition presentation can access and transform to each other, it is faster when imagery presentation transforms to proposition but not the reverse.