IIRC, the conclusion was that "surprise" is when some low-probability complex hypothesis suddenly rises to prominence. Thus it's not something that describes one of 100000 same-probability events happening, but something that describes one winning a lottery 10 times in a row, or an old lame horse winning the race, in which case you start suspecting that something is going on. If a low-probability event doesn't give a hint that something unexpected is going on, there is no surprise.

The emotion of surprise itself is possibly an adaptation that tells the brain to pay attention, to try to figure out what that new unexpected phenomenon might be and what else that entails.