Egocentric and relative spatial codes in S-R compatibility

Summary It has been shown that spatial compatibility is due to a comparison between the spatial codes that describe stimulus and response positions. Such codes are often defined in right-left terms. There are, however, two types of right-left codes that can be used for describing a position in space. One is formed with relation to the egocentric axes and can be termed side, whereas the other is formed with relation to an external reference location and can be termed relative position. Five experiments were conducted to determine the role of these different codes in producing spatial compatibility effects. In Experiments 1 and 2 the position of the stimulus provided the relevant cue for choosing the correct response (i.e., the situation was typical of spatial compability proper), whereas in Experiments 3, 4, and 5 the stimulus provided a locational cue that was not necessary for choosing the correct response (i.e., the situation was typical of the Simon effect). The experimental manipulations concerned the task demands and the time elapsing between availability of the stimulus code and availability of the response code. The results showed that upon stimulus presentation, both stimulus codes (that concerning side and that concerning relative position) were formed, but experimental manipulations determined the one that was effective in yielding compatibility effects. When the task required the use of one type of code, then spatial compatibility depended on that code alone. When the two coding processes were separated in time, then spatial compatibility depended only on the code that was formed simultaneously with the response code.