I am mainly interested in how humans perceive and recognize others. To find out, I use event-related brain potentials (ERPs). ERPs can be calculated from the human encephalogram (EEG) – small voltage changes recorded from the scalp, which reflect electrical activity of the brain. ERPs have an excellent temporal resolution, and are therefore particularly suited to test at which point in time particular processes of interest occur. This, in turn, can be used to to test psychological theories about how the mind works, and more specifically, how face perception and memory is achieved.
The figure below shows shows an ERP of a single participant (me!). Solid lines represent trials in which upright faces were presented, dashed lines represent faces that were inverted, i.e., rotated by 180°. Face inversion is known to interfere with face perception and recognition, and a specific ERP component, the so-called N170, is sensitive to this modulation. N170 (the time range between the vertical dotted lines) is typically larger and increased for inverted faces (see e.g., Bentin et al., 1996; Rossion et al., 2000; Eimer, 2000). It can be inferred that face inversion acts at an early perceptual processing stage.