are selected using the terminal cursors. Thus, the ratio between the distances 
separating the points in Bugspace and in physical space yields a factor or 
proportionality between Bugwatcher units and conventional units of spatial 
measurement (e.g., gm, mm, cm, etc.). 
Experimental Parameters and Experimental Variables 
Biological interpretation of behavioral data requires that the behavior of 
organisms be related to experimental conditions prevailing at the time of 
observation. Consequently, we have developed methods to associate 
experimental parameters and experimental variables with sets of data. An 
experimental parameter is a quantity characterizing a condition which is 
constant throughout any given record but may vary from record to record 
(e.g., temperature, concentration of a pollutant, etc.). Using the PARAMETER 
operator, such numerical constants may be inserted into the set of attributes 
belonging to each data vector. Parameters may be deleted, modified or listed. 
They may be used to organize graphical displays (e.g., average linear velocity as 
a function of temperature) or to modify the execution of certain operations. 
An experimental variable is a quantity whose value changes during a single 
record. Times at which simple step changes in stimulus conditions (e.g., 
switching a light on and off) occur may be indicated by the presence or 
absence of tones stored on the audio track of a video tape. The Bugwatcher 
possesses four tone generators to produce such temporal markers during the 
course of an experiment; it also possesses external connections which allow the 
simultaneous gating of laboratory apparatus. When the video tape is replayed 
into the Bugwatcher these tones are detected. As discussed above, the second 
attribute in each data vector sent to the computer contains four bits dedicated 
to representing the presence or absence of the four tones. 
We are presently developing a technique which provides for the 
representation of stimuli which vary continuously over time. The stimulus level 
will be encoded by means of frequency modulation (fm) on the audio track of 
the video tape. When the tape is replayed into the Bugwatcher the fm signal 
will be digitized and represented with 10-bit precision by the fourth attribute 
of each data vector sent to the computer. The APPEND operator will be 
employed to extract this information from each data vector, scale it and store 
as an equispaced time series. Again these data may be used to organize 
graphical displays or they may enter into computations involving time series of 
behavioral variables. One of us (Wilson) is preparing to employ this method to 
investigate behavior evoked by rotation of the plane of polarized light. The 
organisms swim beneath a polaroid filter whose angle is controlled by an analog 
servomechanism. The filter may be rotated so as to describe quick jumps, 
ramps, harmonics, etc. A signal directly proportional to the angle ol the filter 
will be encoded and analyzed. 
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