system. Finally, we outline work now in progress to further generalize the 
Bugsystem to provide for the analysis of movement in three dimensions. 
DEFINING A BEHAVIORAL RESEARCH LANGUAGE 
The Behavioral Research Language, or BRL, is a high level operator based 
language that is tailored to the unique problems associated with the input, 
scaling, analysis and display of video images of moving objects. BRL is an 
interpretive language which runs as an application program on a good sized 
minicomputer and relies heavily upon user interaction with a storage graphics 
terminal to input, plot, edit and transform the data through image processing 
functions. Image processing generally culminates in the computation of paths 
or trajectories of the objects moving before the video camera. Sets of 
trajectories may be merged together and the data may be transformed to yield 
time series of behavioral variables (e.g., linear velocity, angular velocity, 
direction of travel, etc). These results may then be analyzed statistically, and 
the resultant data sets either listed numerically or plotted on the graphics 
terminal. Thus, the Bugsystem consists of two basic subsystems: (1) an unique 
image processing system for the frame-by-frame analysis of video data; and (2) 
a signal processing system for the statistical analysis of equispaced time series. 
The key element to understanding and using BRL lies in grasping the 
operator-operand-resultant nature of specifying functions or commands to the 
system. The general command syntax is as follows: 
*Operator/sw/sw Operand-name/sw/sw Resultant-name/sw/sw nl, . . . n5, 
Where “*” is the prompting character, “Operator” is one of the available 
functions (of which there are currently 88, with the list still growing), 
“Operand-name” is the name of the input (or operand) data set, and the 
numeric constants “nl” through “n5” are optional numeric constants which 
govern details of the function of certain operators. The “/sw” denote optional 
“switches” (the word is taken from minicomputer jargon) which are used as 
operator modifiers or to supply special information to the operator being used. 
All data sets are disk resident and are specified by a four-letter name that can 
be used to denote an experimental condition, a two-letter extention that 
specifies the type of data represented (e.g., “VI”-video, “PA”-path, 
“LV’Minear velocity, “CA”-catergorized, etc.), and a six letter front name that 
can be used to identify the species studies and/or the date of the experiment. 
The front name must be specified only when starting the system and remains 
unchanged unless it is explicitly modified by the LOAD operator. Operator 
names will henceforth be in bold upper case letters in the text. 
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