How fast can we recognise a famous face?
Even under extreme time pressure, people need at least about 360-390 milliseconds to recognise a famous face among unfamiliar ones, much longer than simply detecting a face.
Source
Fast and Famous: Looking for the Fastest Speed at Which a Face Can be Recognized
Study at a glance
- Design
- Human experiment — Speeded go/no-go famous-versus-unknown face task; Experiment 1 used strong speed encouragement, Experiment 2 added a 600 ms response deadline with audio feedback (the SAB procedure); minimal RT estimated from when hits first reliably outnumber false alarms
- N
- Experiment 1: 31 volunteers. Experiment 2: 101 recruited, 14 failed the task leaving 87, of whom a minimal RT could be computed for 57
- Population
- Healthy young adult volunteers with normal or corrected-to-normal vision
- Outcome
- Minimal reaction time (minRT) for correct famous-face responses, median RT, d-prime sensitivity and response bias C
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What they did
In Experiment 1, 31 people saw photos flashed for 100 ms and lifted their fingers as fast as possible only when the face was famous, with feedback and encouragement to beat their times. Experiment 2 tested 101 people with a stricter 'speed and accuracy boosting' procedure: responses had to come within 600 ms and each answer received immediate positive or negative audio feedback. The key measure was each person's minimal reaction time, the earliest point at which correct 'famous' responses significantly outnumbered false alarms.
What they found
In Experiment 1 the median minimal RT across people was 555 ms, but the two fastest participants reached 390 ms with normal accuracy. In Experiment 2 the median minimal RT dropped to 420 ms and the fastest individual was 360 ms (350 ms pooled across all trials). Faster people were also more accurate in Experiment 2, so there was no speed-accuracy trade-off, and participants responded less conservatively than in Experiment 1. The authors conclude recognition cannot happen faster than about 360-390 ms.
The limits
What it doesn't show
The two experiments used different stimuli (whole photos in context versus cropped grey faces chosen as the most recognisable), so their results cannot be compared directly as a pure test of the procedure. It measures familiarity for celebrities only, not personally known or newly learned faces, and the task can be done on a feeling of familiarity without full identification. The neural interpretation about the perirhinal cortex and feedback processing is inferred from reaction times and prior literature, not measured in this study. In Experiment 2, 14 people failed the task and a minimal RT could not be computed for many others, so the estimate rests on a subset.
Key terms
- Go/no-go task
- A task where people respond to one category of stimulus (go) and withhold responses to another (no-go).
- Minimal reaction time (minRT)
- The earliest time bin at which correct responses significantly outnumber incorrect ones, estimating the fastest reliable processing speed.
- Familiarity vs recollection
- Two proposed memory processes: a fast feeling of having seen something before versus slower retrieval of specific details about it.
- Speed and Accuracy Boosting (SAB)
- A procedure combining a response deadline with audio feedback to push people to their fastest accurate strategy.
- d-prime and bias C
- Signal detection measures of how well targets are discriminated from distractors, and whether responding is conservative or liberal.
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Quiz yourself
What is the approximate fastest time at which people can recognise a famous face in this study?
Common questions
Why not just use average reaction times?
Averages include slow, deliberate responses; the minimal RT isolates the fastest point where people are reliably above chance, which better estimates the speed limit of the process.
Why does 360 ms matter for brain theories?
Subtracting roughly 100-130 ms for decision and movement implies familiarity signals are ready by around 260 ms, later than the 170 ms face-sensitive EEG component, suggesting recognition needs processing beyond early face areas.
Is recognising a face slower than detecting one?
Yes; detecting that a face is present in a scene takes about 250-290 ms behaviourally, and the authors estimate that recognising a face takes roughly 100 ms longer than categorising an object.
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