Recording, Analyzing, and Displaying Spatio-Temporal Position Data

Abstract

Many psychological investigations require the precise measurement of the spatial position of an organlsm (or a body part) at successive temporal intervals. This type of study generates large quantities of data. A manual analysis is usually not exhaustive and detailed because l r 1s tedious, time-consuming, and expensive to perform. The techniques of Haith (1 ) and Herron and Frobish (2 ) may be combined to provide a semiautomatic procedure for recording, analyzing, and displaying spaao-temporal position data. Haith (1 ) has developed a semiautomatic recording technique. Successive spatial positions were recorded on motion picture film. Each film frame was projected onto a screen which had a grid of wires in front of it. Touching a metal probe to the vertical and horizontal wires which formed the coordinates of the point to be measured automatically punched rhe Cartesian coordinates into IBM cards. Herron and Frobish. ( 2 ) have described an automatic method for analyzing and displaying movement patterns of one or more organisms within a spatial field. Positions were recorded using time-lapse photography. The photographs were of children in a play area using 10-sec. intervals over several play sessions. Each child's position on each frame was manually recorded as Cartesian coordinates by estimating his position relative to a grid of 3-ft, squares painted on the floor. The coordinates were punched into 1BM cards which served as input to an IBM 7094 computer and a CalComp 670-564 (California Computer Products) plotter. The computer-plotter was programmed to yield a number of numerical and graphical descriptions for each session and over all sessions, viz., distances travelled, distances between children, frequency o f entry into specified territories, frequency of solitary activity in each territory, and frequency of accompaniment by selected permutations of other children in each territory. Numerous other analyses are possible once position data have been recorded as Cartesian coordinates. Since Haith's appararus requires special construction, it is desirable to consider an alternative semiautomatic procedure which uses hardware already available. A graphical input device, e.g., a CALMA Digitizer, may be used to record position data on dlgital magnetic tape. It may be applied to either positives or negatives obtained from either motion pictures or time-lapse photography. The reference coordinate system may be placed either on the floor or superimposed over each frame with a template. The digitizer is used to identify the experiment, run, and number of each frame, and a manual stylus locates the position of each person with respect to the coordinate system. Thus, a tape is produced containing a number of frames of position data for analysis and display by the computer-plotter system. Programs mag be applied to correct for lens magnification and pin cushion distoraon.