Does the complexity of S2 have any effect upon RT1? A controversy in the PRP literature

Area of Science:

• Cognitive Psychology
• Human Factors
• Psychophysics

Background:

• The Psychological Refractory Period (PRP) effect describes a delay in responding to a second stimulus when it closely follows a first stimulus.
• Existing theories propose various mechanisms, including central processing bottlenecks, for the PRP effect.

Purpose of the Study:

• To examine how varying the complexity and uncertainty of stimulus-response (S-R) pairings influences reaction time (RT) within the PRP paradigm.
• To test specific hypotheses regarding the impact of S2-R2 complexity on RT1.

Main Methods:

• A within-subject Latin square design was used with 12 undergraduates.
• Four conditions manipulated S-R complexity: simple-simple, simple-choice, choice-simple, and choice-choice.
• Stimulus-response mapping involved visual stimuli (up to 4 lights) and manual responses (up to 4 key presses).
• Uninformed catch trials were included, and interstimulus intervals (ISIs) varied randomly (100-400 ms).

Main Results:

• No statistical evidence supported the hypothesis that increasing the number of choices for the second stimulus-response (S2-R2) lengthens the reaction time for the first stimulus-response (RT1).
• The complexity of the second task did not significantly impact the reaction time of the first task under the tested conditions.

Conclusions:

• The findings challenge explanations of the PRP effect that rely solely on a strict central bottleneck model.
• Results are discussed in the context of parallel-processing models, suggesting that some processing of the second task may occur concurrently with the first.