RECDIS: A BASIC program for computing interindividual distances within a rectangular area

Abstract

A variety of investigators have observed freely behaving rats in circular open fields and have used interindividual distances as a quantitative measure of social attraction or gregariousness (Barefoot, Aspey, & Olson, 1975; Eckman, Meltzer, & Latane, 1969; Latane, 1969; Latane, Cappell, & Joy, 1970; Latane & Glass, 1968). To facilitate such raw data collection and organization, Aspey (in press-b) developed a computer program (CIRDIS) for determining interindividual distances between any two subjects when observed in a circular open field marked off into 49 sectors. The program RECDIS refers to distances, and extends the generality and applicability of determining interindividual distances by specifying locations in terms of numbered sectors to rectangular test areas of variable length and width. The program is written for a rectangular test area marked off into any number of identified squares of equal size and shape. Length and width are user specified, and the program is applicable to a variety of research situations whenever two animals' locations can be specified in terms of the N squares. In an ethological research example, Aspey (in press-a) computed the theoretical personal space among groups of adult male wolf spiders by determining interindividual distances during agonistic encounters when tested under varying social, spatial, and population densities. Diagrams of the rectangular area, marked off into a numbered grid (Figure 1), make useful data sheets for recording subjects' locations during testing, or for transcribing tape-recorded protocol. Additionally, a theoretical, chance interindividual distance can be computed by entering all combinations of the numbered squares and obtaining the mean of all possible distances. Furthermore, control distances can be computed by recording each partner's location when tested alone and computing the distances as if the partners had been tested together. This measure provides an indication of the expected interindividual distance between subjects if they were to move through the rectangular field independently of each other. Description. After operationally defining location (e.g., as that numbered square where a spider's right palp is located during a given trial), the numbers of the squares are recorded where each member of a subject