The auditory system has an amazing ability to rapidly encode auditory rules. Evidence comes from the classic oddball paradigm, in which frequent (standard) sounds are occasionally exchanged for rare (deviant) sounds, which then elicit signs of rule violation (e.g., MMN, P3a, performance decline). It is less clear whether deviants, which also carry certain rules, contribute to internal models of the auditory environment although they are encountered less often than standards.

To investigate this, we developed a novel, conditional oddball paradigm: two kinds of deviants differ in their probability of repetition. Depending on repetition probability, the sound actually following a deviant (another deviant or a standard) is conditionally likely or unlikely. Independently, this sound is either unlikely (deviant) or likely (standard) with respect to the global rule (i.e., overall stimulus probability). This dissociation allows for probing rule extraction from rare events.

I will present robust empirical findings at the level of response times and false alarm rates (three studies, altogether 160 participants), demonstrating that conditional rules associated with rare deviants can be extracted when behaviourally relevant (active deviant detection task). I will discuss electrophysiological findings in a passive listening setting (two studies, altogether 120 participants) with respect to what rules the auditory system relies on when all sounds are to be ignored.

Altogether, I will show how disentangling the type of information (conditional vs global probability) from the frequency of rule encounters (rare vs frequent) provides novel insights into how our brains cope with the complexity and dynamics of the world.