Not All Rules Are Equal: Rare Conditional Rules Shape Behaviour but Yield to Global Probability in Passive Listening

Area of Science:

• Auditory Neuroscience
• Cognitive Psychology
• Human Auditory System

Background:

• The human auditory system efficiently processes sound patterns, often using the oddball paradigm to study responses to predictable (standard) and unpredictable (deviant) sounds.
• Deviants typically trigger prediction error signals like the mismatch negativity (MMN) and P3a, but their role in informing auditory predictions, especially less frequent ones, is less understood.

Purpose of the Study:

• To investigate whether less frequent deviant sounds, despite carrying predictive information, influence auditory prediction.
• To examine how the auditory system processes conditional probability information from deviants versus global probability information from standards.

Main Methods:

• A modified oddball paradigm was used, presenting sequences where deviants could be followed by the same deviant (repetition) or a standard sound, creating conditional likelihoods.
• Participants engaged in both active deviant detection and passive listening tasks to assess behavioral and neural responses.

Main Results:

• Behaviorally, participants utilized conditional probability information from deviants when it was relevant to the task, showing increased response times over the task.
• However, neural responses (MMN and P3a) in passive listening were sensitive only to violations of global probability rules, not conditional probabilities from deviants.
• Observed sensitivity to conditional probability in neural measures was minimal compared to global probability effects.

Conclusions:

• The auditory system appears to primarily rely on frequently encountered regularities (global probability) for auditory prediction, particularly during passive listening.
• Predictive information from less frequent deviant sounds is extracted behaviorally when task-relevant but does not significantly modulate early neural responses in a passive setting.