Abstract
We examined the relationship between orienting (exogenous vs. endogenous) and selection (space-based vs. object-based) of attention. The cueing paradigm of Egly, Driver, and Rafal (1994) was adopted because the cue-validity effect and the same-object effect, which are indicative of space-based and object-based selection respectively, can be observed in the same task. Moreover, with the manipulation of cue informativeness (i.e., cue validity), exogenous and endogenous orienting could be induced alone or simultaneously in this paradigm. When the same informative peripheral cue as in Egly et al. (1994) was used, in which both endogenous and exogenous orienting were assumed to be induced, both the cue-validity effect and the same-object effect were obtained (Experiment 1). When an uninformative peripheral cue was applied to induce pure exogenous orienting, only an inhibition of return (IOR) at the cued location was obtained (Experiment 2). Experiment 3 used the same informative peripheral cue as in Experiment 1, but the object disappeared after the cue display for 200 ms (Experiment 3A) or 80 ms (Experiment 3B) before the target appeared. Results showed that the cue-validity effect was observed, but not the same-object effect. Thus, the same-object effect vanished under the two manipulations by either excluding the endogenous orienting (Experiment 2) or making the object disappear (Experiment 3). The cue-validity effect (Experiments 1 & 3), on the other hand, changed into an IOR effect with pure exogenous orienting (Experiment 2). We conclude that endogenous orienting is necessary but not sufficient for object-based selection, and that it modulates the space-based representation upon which exogenous orienting operates.
Supported by the National Science Council of Taiwan, NSC91-2413-H-002-013