Neuropsychology
Face Recognition Detective
Recognising someone is not one step. Put a difficulty somewhere in the model, see which tasks notice, then work backwards from six fictional profiles.
Simulated - schematic faces generated from seven numbers, fictional cases, no assessment of anybody
Learning objective
By the end you should be able to say which step of person recognition a profile implicates, and why the voice route decides it.
About 30 minutes, in two experiments. Nothing you do here is saved or sent anywhere.
This is not a test, and not a diagnosis
Nothing here assesses the person reading it: no self-test, no score for you, and nothing that can tell anybody whether they have difficulty recognising faces.
All six cases are invented. The faces are drawn from seven numbers by a seeded generator and resemble nobody. No photograph, no published test and no real person appears.
- Experiment 1. Put the difficulty at one component and read down the seven task outcomes. Then move it.
- Notice which components spare the voice route and which do not.
- Experiment 2. Six fictional profiles. Work backwards to the component - and decide when you cannot.
First, a judgement
A fictional person says they no longer recognise colleagues by sight. On testing, they can tell any two unfamiliar faces apart without difficulty, and they know exactly who a colleague is the moment that colleague speaks.
The model
- 1 Forwards, from component to profile
- 2 Backwards, from profile to component
Key terms
- Component
- One step in the sequence this model uses to get from a face to a name. The difficulty is placed at exactly one of them.
- Familiarity
- A sense of having met this person before, with nothing else about them necessarily available.
- Name retrieval
- Producing the person's name. The model treats it as a later step than recognising who they are.
- Voice route
- Reaching the same information about a person from their voice rather than their face. Some tasks here use it; others cannot.
- Control task
- A task included so that a low score elsewhere can be read as selective rather than as part of a general difficulty.
Experiment 1 - forwards, from component to profile
Goal
The model, with the difficulty marked
The seven tasks
Reading this
The seven tasks and what each one needs
| Task | What it asks for | Components it needs | Outcome |
|---|
The faces used here, and why they look like that
Each face is drawn from seven numbers - head width, chin width, eye spacing, eye height, eye size, nose length and mouth width - chosen by a seeded pseudo-random generator. The seed is printed beside them so a demonstrator can reproduce the same set. They are schematic on purpose: no photograph is used, no published test stimulus is reproduced, and no drawn face here corresponds to any real person. Nothing in the model depends on what the faces look like.
Challenge - a claim to weigh
What this demonstrates
Recognising someone is several things in a row
Seeing a face well enough to tell it from another face, finding that face familiar, knowing who the person is, and producing their name are separable steps. They separate because they can be affected independently, and the evidence for that is exactly the pattern you have been building: a difficulty at one step leaves everything before it intact and everything after it stranded.
The second route is what makes the argument
People can also be recognised by voice. A difficulty that ruins recognition from the face while leaving recognition from the voice untouched has to sit on the face route, before the two converge. A difficulty that ruins both sits after they converge, and is therefore not about faces at all. Without the voice tasks, those two very different accounts produce the same face-task profile.
The control task is not optional
Face perception and general visual processing produce identical profiles on every face task. The only thing that separates them is a non-face task - and only if the objects are as hard to tell apart as the faces were. Faces are unusually similar to one another, so an ordinary object task is easier, and an easier task can look intact for reasons that have nothing to do with faces.
Some profiles have no answer
Profile E is below range on all seven tasks, including the voice route and the object task. No single component in this model produces that. Before reaching for a component, the explanations to consider are effort, fatigue, low-level vision such as acuity or contrast, mood, general slowing, unfamiliarity with the specific faces used, and testing in a language or a face population the person has less experience with. Most of these are easier to check than any of the components.
Real difficulties are heterogeneous
Face-recognition difficulties differ in which component is affected, in how severe they are, in whether they were acquired after an injury or present from early life, and in how much a person has learned to work around them using hair, voice, gait, context and clothing. Two people with the same label can have very different profiles, and a profile is a description of tasks rather than a description of a person.
For teaching elsewhere: take this activity as one self-contained block of HTML, on the clipboard or as a file. Either way it is styled so that it will not disturb the page you put it into.