Most of the time it feels as though our perception of the world is based on what’s out there, what psychologists call ‘stimulus-driven’ or ‘bottom up’ processing. But in reality, our perceptual experience is a seamless mixture of both what really is out in the world and what we expect to be out there (so-called ‘top down’ or ‘concept-driven’ processing). Tom gave an elegant example of this in a recent post, describing how so many people hadn’t noticed the erroneous use of the word ‘conservations’ in the Mind Hacks book, when it should have said ‘conversations’ – in this case readers saw what they expected, not what was written.
I was struck by a couple of similar examples in recent visits to the gym. On the first occasion I’d just finished on the running machine where I have to really crank up my MP3 player volume to drown out the loud music played over the public speakers. When I sat down in the far quieter weights section, the volume on my headphones suddenly felt painfully loud in this quieter environment, and so I quickly jabbed the volume down a few notches. I felt such a relief as the music gradually softened and my eardrums were saved. It was only much later that I realised my MP3 player’s controls were in the lock position – I hadn’t turned the volume down at all. My expectations had overridden the true information arriving at my senses.
On my next visit I proudly grabbed two 14kg (don’t laugh!) dumbbells for some bicep curls. I’d worked up to this weight over recent months and considered it my limit. I was pumping away but my left arm was really struggling, which I put down to it being my weaker arm. Still, I persevered and did my usual number of reps. It was only when I went to replace the dumbbells that I saw the weight in my left arm was 18kg! – someone had put the weights in the wrong places… Well, I thought, maybe I’ve not been pushing myself enough, but no, later on when I went to try out some curls with 18kg weights, it was hopeless: when I ‘knew’ what the weight was it ‘felt’ too heavy!
Anyone got some other examples?


Sex and relationship psychologist 
There’s a raft of new articles just appeared on 


Last Saturday’s Guardian featured an 