Time-dependent effects of perceptual load on processing fearful and neutral faces.

High perceptual load is thought to impair the early processing of task-irrelevant distractors. In contrast, for emotional faces, previous studies have shown that early event-related potentials (ERPs), the P1, the N170, and, albeit to a lesser degree, the EPN, are relatively resistant to perceptual load manipulations. However, the temporal dynamics of the interaction between load and processing of emotional distractor faces have been neglected so far. In this preregistered EEG study (N = 40), we investigated effects of perceptual load and different interstimulus intervals (ISIs) on ERPs to fearful and neutral task-irrelevant faces. We used a task with identical visual input regardless of perceptual load (high vs. low), and four ISIs between task and face onset (100 ms, 300 ms, 600 ms, 900 ms). Results show that emotional ERP modulations depend on load manipulations as well as on specific ISIs between the perceptual task and face onset. Emotional P1 effects were modulated by load, irrespective of the ISI, while emotional N170 and EPN effects were independent of load, but modulated by the ISI. In particular, emotion effects for the EPN were only observed after a prolonged period between load task and face onset (ISI900), suggesting a strong vulnerability of this component to any competing task. Taken together, our findings show that early ERP components for fearful expressions show dissociable responses to load and timing manipulations.