Visual Similarity of Pen Gestures

Comments:
1. Nabeel's Blog
Summary:
Gestures, a powerful feature in Pen based UI, are commands issued with a pen. Factors that affect selection of gestures are similarity among gestures, difficulty in learning gestures and wrong recognition by the computer.A pair of experiments is conducted to measure the similarity among gestures and derive an algorithm for computing the similarity.To analyze the date collected, Multi-Dimensional scaling technique is used. This technique reduces the number of dimensions in the data set so the patterns can be seen by viewing a plot of the data (2/3 dimensions). The gesture set chosen in the first experiment were based on 2 criteria: span a wide range of gestures and to include variation in orientation. Data was collected from 21 people. Analysis of the plots of gestures generated by MDS helped author to determine the geometric properties which influenced the users perceived similarity. Regression analysis helped the author develop a model of gesture similarity which can predict how people perceive 2 gestures. Similarity of the gestures were given by the euclidean distance between their features. Smaller distance means greater similarity. Regression analysis produced weights for different features in determining the similarity.The authors were able to derive a model which predicts gesture similarities with 0.74 correlation with reported data.Second experiment had 3 gesture sets with each set used to check the effect of variation of particular features on similarity perception.Though this goal could not be completely achieved since some features co varied with others.The derived model predicted reported gesture similarity with 0.71 correlation. The analysis of first gesture set (effects of absolute angle and aspect) gave 3 dimension with MDS plot. It showed that absolute angles in the set co varied greatly that it was difficult to determine if it was significant.Analysis of second gesture set shows that neither length nor area and significant in similarity judgement.Analysis of third gesture set showed that gestures whose lines were horizontal and vertical were perceived similar.

Discussion:
In both the experiments, the users were unaware of the operations a gesture is mapped to. It would interesting to find if there is a link between the context in which the gesture is used( application with which an user is interacting), operations performed by the gestures and the way user perceives a gesture.