Faces are encountered across a huge range of visual conditions, including differences in light, distance and visibility. To accurately detect all faces under all these conditions, the face detection system must be suitably generalized. However, in autism spectrum conditions (ASCs), the typical generalization of perceptual learning is narrower. Here, we tested the generalization of the face detection system in a sample of adults with ASCs and a matched control group without ASCs. We recorded electroencephalography while participants viewed images of actual faces, face-like objects and non-face-like objects. Analysis of the N170 event-related potential component, which is related to the early stages of face detection, showed that the two participant groups were comparable in the activation of the N170 to actual faces and face-like objects, but that the typical control group showed an increased N170 for non-face-like objects over the group with ASCs. This indicates that the face detection system is less generalized (narrower) in ASCs than in typical development. We propose that the reduced social interest characteristic of ASCs is associated with a narrower face detection system that is less reliable in detecting all the faces in the environment.