Examination of factors affecting the intraoral perception of object size: a preliminary study

Oral sensory function is essential for the successful performance of a range of ingestion. Although the perception of object size is important in determining the degree of manipulation, evidence suggests that people does not always perceive the size of the object in oral cavity accurately. The purpose of this study was to investigate the factors affecting the intraoral perception of object size. Twenty-three healthy young volunteers detected the size of cylinders inserted into oral cavity blindly and identified it from the reference set. The diameter of cross section varied from 10 to 14 mm in a gap of 1 mm and had three different temperatures (5, 36, 50 °C) in each. The perceived size was recorded, and the difference with the actual size was assessed. The required time for identification was also measured and compared between gender and between temperatures. The results demonstrated that the direction of size illusion was significantly affected by the required time for identification. Long manipulation led to overestimation, and short manipulation led to underestimation of object size irrespective of temperature and size. Gender was the other factor affecting intraoral size perception. The rate of overestimation was low in female participants comparing with male participants in this experiment, although the number of participants was limited. We therefore concluded that in order to detect the other factors affecting intraoral size perception, regulating oral manipulation time is indispensable.