Some changes to our mental world take place gradually. An orchestra comes to a crescendo, and then fades back to nothing, all the while playing the same chord. As the listener, we experience a graded change in volume. But other changes are more immediate. When squinting to read a street sign from a distance, there is a moment when you suddenly “get it”, and know what it says. There is no way in which the sign gradually becomes more or less intelligible. This is an example of categorical perception.
Might knowledge of ourselves be similar?
A study by Katerina Fotopoulou and colleagues sheds light on this issue. She focussed on a fascinating case of recovery from anosognosia. Anosognosia (from the Greek meaning “without knowledge”) is the term given to a lack of awareness or insight into a particular neurological condition. In extreme form, anosognosia can result in very bizarre symptoms, such as Anton’s syndrome, where cortically blind patients claim to be able to see. Dr. Fotopoulou’s patient was a 67-year-old lady who suffered from hemiplegia – paralysis of half of the body following a right-hemisphere stroke. However, she claimed to be able to move her arm, and breezily asserted that she could clap her hands. At least, until Dr. Fotopoulou showed her a recorded video of herself being examined:
“As soon as the video stopped, LM immediately and spontaneously commented: “I have not been very realistic”. Examiner (AF): “What do you mean?” LM: “I have not been realistic about my left-side not being able to move at all”. AF: What do you think now?” “I cannot move at all”. AF: “What made you change your mind?” LM: “The video. I did not realize I looked like this”.”
This altered self-awareness was still present 6 months later. It appeared that allowing the patient a third-person perspective on herself had removed her anosognosia, and led to changes in the representation of her own body. While this is a single case report, and may not work for all patients, the data are tantalising. In particular, they suggest that onset of self-awareness can be sudden and transformative. This makes sense – we all have experienced the “aha” moment accompanying retrieval of the name of that actor that you couldn’t drum up during dinner the previous evening. Changes in awareness of the self may share similarities with other domains of categorical perception. Whether this mental plasticity is accompanied by a rapid form of neural reorganisation, or a “change in the software”, remains unknown.