Stimulus onset asynchrony

Stimulus-onset asynchrony (SOA) is a measure used in experimental psychology.

In this respect, a stimulus may consist of, e.g., a presented image, sound or printed word.

A short time interval between S1 and S2 may lead to interference in the neural processing of these two patterns.

Conversely, a very long SOA may lead to a situation where the brain activity caused by S1 may have faded, such that S2 has become an isolated event.

Typical research questions concern the facilitation, deterioration, or biasing effects of the sequential stimulus presentation on a required later response.

Figure 1. Time diagram for a trial in a psychological experiment. The stimulus-onset asynchrony (SOA) between the first presented pattern (S1) and the second stimulus (S2) is manipulated in order to measure an effect on reaction time (RT). Usually also the correctness of the response is studied.