Thursday, 14 February 2013

The importance of context (even for recognising family!)

I've been using the face recognition feature in my photograph management software. It was coming up with some suggestions that were pretty impressive (e.g. finding several additional photos that featured my mother, when primed with a few) and some that felt a little spooky (e.g. suggesting that a photo of me was actually of my mother – something that probably none of us wants to admit to, however attractive the parent). But it was also making some inexplicably bizarre suggestions – e.g. that a male colleague might be one of my daughters, or that a wine glass might be a face at all. This recognition technology is getting very sophisticated, but it clearly does not recognise faces in a human-like way!

From a computational perspective, it does not account for context: it identifies and matches features that, in some low-level way, correspond to "face", and it gets that right a lot of the time, identifying real human faces and artificial faces (such as a doll). However, it does not have the background knowledge to do the gender- and age-based reasoning that people naturally do. This makes some of its suggestions seem bizarre. And the fact that it works with low-level features of an image is really exposed when it suggests that a wineglass should be named.

From a human perspective, context also matters in recognition. For most adult faces that were close friends or relations, recognition was generally straightforward, but for children or less familiar people, it was almost impossible to recognise people out of context. The particular software I was using did not allow me to switch easily between detail and context, so there are some faces that are, and will remain, unlabelled, meaning that I won't be able to find them again easily. For example, with context, it was instantly apparent who this small child was: she was sat on her (recognisable) mother's knee, with her big sister at her side. But without that context, she is a small (and slightly uncomfortable-looking) blonde toddler. Context matters.

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