Why Some Celebrities Match So Many People
Picture every face as a point in space, with similar faces close together. Most faces crowd around the middle, the average. Fewer sit out at the edges. A celebrity whose face is near the middle has many people close by. A celebrity with a very distinctive face, far out at the edge, has few.
So when lots of people search, the celebrities near the middle come up again and again. Not because they're more famous or more photographed, but because their face is close to a large number of other faces.
The Most "Average" Faces in Ollie's Index
The Ollie team averaged the embeddings of every celebrity in the index (over 5,000 people) to find the centre of the model's face space. The celebrities closest to that centre included:
- Robert Downey Jr.
- Isabella Rossellini
- Margaret Qualley
- Mikey Madison
- Jeffrey Dean Morgan
"Average" here is a compliment, and not just politely. Face research since the 1990s has found that faces close to the average of a population tend to be rated as more attractive. See what attractiveness research tells us.
It also doesn't mean these faces look generic. "Average" here means average across 512 numbers at once, which is a very different thing from looking ordinary.
Read more: Why Some Celebrities Get Matched More Than Others
Hubness: A Quirk of High Dimensions
There's a second, more mathematical reason. In 2010, Miloš Radovanović, Alexandros Nanopoulos and Mirjana Ivanović published "Hubs in Space", describing an effect that appears in high-dimensional data. When you find each point's nearest neighbours, a few points turn up as the nearest neighbour of far more points than expected. They called these points hubs.
The effect gets stronger as the number of dimensions grows, and face embeddings have 512. Points near the centre of the data tend to become hubs. So in any face search system, a handful of celebrities will appear as lots of people's top match, more than averageness alone would predict.
| Type of celebrity face | How often it's matched | How convincing the match looks |
|---|---|---|
| Near the centre (a hub) | Often | Sometimes subtle |
| In a busy region | Fairly often | Mixed |
| Distinctive, at the edge | Rarely | Usually obvious |
What It Means for Your Results
If your top match is a celebrity who seems to be everyone's top match, two things could be going on. Your face may genuinely be close to theirs, or you may simply be in the busy middle where they act as a hub.
Here's how to tell:
- Check the gap. If your first match is well ahead of the rest, it's probably specific to you. If all five scores are bunched together, you're in a crowded region.
- Look at your other four. Matches that share a specific feature with you (the same brow, the same jaw) are more telling than one hub celebrity.
- Repeat with other photos. A hub may stay at the top across photos too. If a more distinctive celebrity keeps appearing in your top five, that one is likely a more specific match.
Read more: Celebrities Who Look Alike, According to an AI
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Distinctive Faces: Fewer Matches, Better Ones
Celebrities with unusual features, say very wide-set eyes or a strong, angular jaw, sit out at the edges of face space. They don't come up often. But when they're your top match, it usually means you share that distinctive feature, and people tend to see the resemblance immediately.
This matches research on human memory too: distinctive faces are more memorable because they have fewer neighbours in our mental face space. See what makes a face memorable.
Is It Just Ollie?
No. Any lookalike app that ranks faces by distance in an embedding space will show this, because it comes from the geometry, not the brand. Search engines, music recommenders and image retrieval systems all deal with hubness too, and some use corrections to spread recommendations more evenly.
For a lookalike search, a simple correction is the one you can do yourself: look at all five matches and try more than one photo. For other reasons some celebrities appear more often, like how many photos they have, see why some celebrities get matched more than others.