The shape of the face template: Geometric distortions of faces and their detection in natural scenes

- Human face detection might be driven by a simple skin-coloured template.
- We explored the template's shape with horizontally and vertically stretched faces.
- Detection of stretched faces was impaired, even when size was controlled.
- This indicates that the height-to-width ratio of faces is important for detection.
- This result also adds to the evidence that face detection differs from recognition.

Human face detection might be driven by skin-coloured face-shaped templates. To explore this idea, this study compared the detection of faces for which the natural height-to-width ratios were preserved with distorted faces that were stretched vertically or horizontally. The impact of stretching on detection performance was not obvious when faces were equated to their unstretched counterparts in terms of their height or width dimension (Experiment 1). However, stretching impaired detection when the original and distorted faces were matched for their surface area (Experiment 2), and this was found with both vertically and horizontally stretched faces (Experiment 3). This effect was evident in accuracy, response times, and also observers' eye movements to faces. These findings demonstrate that height-to-width ratios are an important component of the cognitive template for face detection. The results also highlight important differences between face detection and face recognition.