The Influence of Spatial Frequencies, Orientation and Familiarity on Face Stimuli Integration

When we observe an object, our visual system identifies its shape and integrates it with specific details to form a coherent representation. This coarse-to-fine approach involves rapid processing of low spatial frequency (LSF) content to generate a basic template, which aids the integration of the more detailed high spatial frequency (HSF) information. Here we explore with two experiments how the contribution of LSF and HSF integration extends to face processing. To do so, we leveraged the face inversion effect, whereby inverted faces are more difficult to recognize than upright ones. In Experiment 1, ten participants matched two familiar faces displayed in rapid succession (template and probe face, respectively). The template and the probe shared either the same SF (congruent) or had complementary SF (incongruent). In congruent conditions, HSF templates yielded better matching accuracy than LSF templates. However, in incongruent conditions, mapping LSF probes onto HSF templates was more effective, but only for upright faces. We propose that, depending on the task, holistic processing may be facilitated by detailed information. In Experiment 2, twelve participants performed the same task with both familiar and unfamiliar faces. While for familiar faces the effects were the same as Experiment 1, for unfamiliar faces the overall accuracy was better for congruent than incongruent conditions, and, crucially, it was independent of the template SF. Our results challenge the view that LSF content provides a foundational template for integrating HSF information, and instead suggest a flexible encoding of SF information, that depends on image contingencies.