We often use many visual clues to determine whether a person is male or female.
Hair length, clothing, and voice pitch all play a part. When just looking at a picture though – especially the ones below where we’ve covered up parts of the face – it can be hard.
Parts of a face that give strong clues about a person’s gender are the eye and brow region (particularly when viewing photos of a face straight on) and nose/chin protuberance (when looking at 3/4 view photos).
We seem to judge faces based on the relationship between facial features (called a configural process), instead of judging individual or isolated facial features.
So, when you can only see one feature (such as the length of a nose), it’s harder to judge whether someone is male or female than when you can see the person’s eye in relation to their eyebrow. (Although even then, it can still be tricky!)