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

experimental psychology Experimental psychology refers to work done by those who apply experimental methods to psychological study and the underlying processes. Experimental psychologists employ human participants and animal subjects to study a great many topics, in ...

. SOA denotes the amount of time between the start of one

stimulus A stimulus is something that causes a physiological response. It may refer to: *Stimulation **Stimulus (physiology), something external that influences an activity **Stimulus (psychology), a concept in behaviorism and perception *Stimulus (economi ...

, S1, and the start of another stimulus, S2 (Figure 1). 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. In one type of study on subliminal stimulation, called "pattern masking," subliminality is achieved by masking the subliminal stimulus with a second stimulus composed of either random parts of letters or numbers, or containing different kinds of figural properties. Here, the critical parameter is the time interval (the SOA) between the onset of the subliminal stimulus and the onset of the masking stimulus. In

psycholinguistics Psycholinguistics or psychology of language is the study of the interrelation between linguistic factors and psychological aspects. The discipline is mainly concerned with the mechanisms by which language is processed and represented in the mind ...

the stimuli are typically a

prime A prime number (or a prime) is a natural number greater than 1 that is not a product of two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime because the only ways ...

and a target, in which case the stimulus-onset asynchrony is measured from the beginning of the prime (S1) until the beginning of the target (S2). This time can be manipulated experimentally to determine its effects on other dependent measures such as

reaction time Mental chronometry is the scientific study of processing speed or reaction time on cognitive tasks to infer the content, duration, and temporal sequencing of mental operations. Reaction time (RT; sometimes referred to as "response time") is meas ...

or brain activity.Harley, T. (2008). ''The Psychology of Language.'' 3rd edition. New York: Psychology Press. p 171. For an example of the application of stimulus-onset asynchrony, see

psychological refractory period The term psychological refractory period (PRP) refers to the period of time during which the response to a second stimulus is significantly slowed because a first stimulus is still being processed. This delay in response time when one is required t ...

References

{{Reflist Experimental psychology