No abstract

In seeking hitherto-unused methods by which users and computers can comrnumcate, we investigate the usefulness of eye movements as a fast and convenient auxiliary user-to-computer communication mode. The barrier to exploiting this medium has not been eye-tracking technology but the study of interaction techniques that incorporate eye movements mto the usercomputer dialogue in a natural and unobtrusive way This paper discusses some of the human factors and technical considerations that arise in trying to use eye movements as an input medium, describes our approach and the first eye movement-based interaction techniques that we have devised and implemented in our laboratory, and reports our experiences and observa tions on them.

In seeking hitherto-unused methods by which users and computers can communicate, we investigate the usefulness of eye movements as a fast and convenient auxiliary user-to-computer communication mode. The barrier to exploiting this medium has not been eye-tracking technology but the study of interaction techniques that incorporate eye movements into the user-computer dialogue in a natural and unobtrusive way. This paper discusses some of the human factors and technical considerations that arise in trying to use eye movements as an input medium, describes our approach and the first eye movement-based interaction techniques that we have devised and implemented in our laboratory, and reports our experiences and observations on them.

Eye gaze interaction can provide a convenient and natural addition to user-computer dialogues. We have previously reported on our interaction techniques using eye gaze [10]. While our techniques seemed useful in demonstration, we now investigate their strengths and weaknesses in a controlled setting.In this paper, we present two experiments that compare an interaction technique we developed for object selection based on a where a person is looking with the most commonly used selection method using a mouse. We find that our eye gaze interaction technique is faster than selection with a mouse. The results show that our algorithm, which makes use of knowledge about how the eyes behave, preserves the natural quickness of the eye. Eye gaze interaction is a reasonable addition to computer interaction and is convenient in situations where it is important to use the hands for other tasks. It is particularly beneficial for the larger screen workspaces and virtual environments of the future, and it will become increasingly practical as eye tracker technology matures.

Intact DNA molecules extracted from HSV-1 (herpes simplex virus 1, human herpes virus 1) strain MP virions have a molecular weight of approximately 97 X 108, but cleavage with the HinIII restriction enzyme yields fourteen fragments with summed molecular weights of 160 X 106. Six "major" fragments occur once in every molecule in the population and account for 60% of the genetic information. Four "minor" fragments are present in amounts equivalent to one copy for every two genomes (0.5 molar ratio) and the other four occur only once in every four molecules (0.25 molar ratio). The minor fragments can be arranged into four equimolar sets, each with summed molecular weights that account for the remaining 40% of the genome. Treatment with lambda 5' exonuclease revealed that all molecules contain 0.5 molar ratio fragments at both termini. These observations and the results of similar analyses of the EcoRI and double HinIII/EcoRI digests indicate that there are four distinct structural forms of HSV DNA which differ only in the relative orientations of two subregions, designated L and S. The L and S segments consist of 82 and 18% of the sequences, respectively, and each has inverted terminally redundant regions that correspond to the internal duplications observed by electron microscopy. The DNA from other strains of HSV-1 and 2 also consists of equal proportions of all four possible permutations of the L and S segments. These unusual features of HSV DNA molecules have novel implications with re ard to the genetic map and the mode of replication and evolution of herpes simplex viruses.Electron microscopic studies have shown that herpes simplex virus 1, human herpes virus 1 (HSV-1) DNA molecules contain internal inverted duplications of their terminal sequences (1, 2). Measurements on "double-looped" structures formed by intact single-strands after self-annealing indicate that 6.0% of the sequences from the left end (designated ab) and 4.3% from the right end (designated ca) have adjacent inverted complements (baac) located internally in the same strand (see Fig. la). Therefore, HSV DNA molecules can be envisaged as consisting of two segments, designated L (82% of the sequences) and S (18%), each containing unique sequences bounded by a large inverted terminal redundancy, i.e., (ab...l...ba) and (ac...s...ca). The duplicated b and c regions were shown to have little if any homology by partial denaturation mapping (2); however, the a regions, at the extreme left and right ends of the molecule, represent a noninverted terminal redundancy of less than 1% of the sequences (Wadsworth, Hayward, and Roizman, in preparation).In another paper in this series (4), we reported evidence for limited heterogeneity in the positions of restriction en-