dependent upon the collection of temporal sequences of spatial information. 

 Cinematography is the classical method used to gather such information. 

 Behavioral variables such as the position of an organism, its orientation, and 

 angles of flection of its appendages are extracted from the motion pictures by 

 means of frame -by-frame analysis. An important advantage of this technique is 

 its flexibility; it may, in principle, be employed in the investigation of any 

 overt behavior which can be photographed. However, two factors preclude the 

 widespread use of this method: (1) manual quantitization via frame -by -frame 

 analysis is a lengthy and tedious process; and (2) once the data is obtained, a 

 substantial amount of subsequent data processing may be required in its 

 analysis. 



The Bugsystem (2, 4, 5) was designed to enable the acquisition and 

 processing of video data by a minicomputer. Behavioral data are initially 

 recorded using standard closed-circuit television equipment. These data are 

 analyzed by replaying a video tape into a specially designed video-to-digital 

 processor (christened the "Bugwatcher"). This device acts as an edge detector, 

 greatly reducing the information flow to the computer and thereby allowing 

 the real-time collection of spatial coordinates delineating the outlines of 

 moving organisms. Frame-by-frame analysis of digitized video data is achieved 

 through the use of specially designed programs tailored to the task of 

 quantizing behavioral variables of interest to the researcher. 



The original version of the Bugsystem was developed by Greaves and 

 implemented on an IBM 1800 computer at the University of California, Santa 

 Barbara. This prototype system, previously described by Greaves (5), has been 

 utiUzed by Hand and Schmidt (6) and by Wilson (8) to investigate the 

 photokineses and phototaxes of marine dinoflagellates. However, several 

 features of this system severely limited the domain of its application. 

 Supported by a research grant from the Environmental Protection Agency, we 

 have developed a second generation Bugsystem. Our explicit goal in the design 

 of this system was to provide a flexible tool for the quantitative investigation 

 of behavior, a system capable of realizing much of the potential of 

 frame -by-frame analytic techniques. 



The purpose of this paper is to describe this second generation Bugsystem, 

 emphasizing the way in which certain hardware and software refinements have 

 expanded the scope of questions which may be conveniently answered by 

 means of "bugwatching." We discuss the way in which the user interacts with 

 the system via a specially formulated "Behavioral Research Language" and the 

 way in which this language has been implemented upon physical machines. We 

 also describe the input of data to the system, the processing and display of 

 behavioral data, and a variety of experimental strategies accommodated by the 



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