Here is the guy who tried to get his own accuracy on imagenet: https://karpathy.github.io/2014/09/02/what-i-learned-from-competing-against-a-convnet-on-imagenet/
Getting 5.1% error was really hard, takes a lot of time to get familiar with the classes and to sort through reference images. The 3% error was an entirely hypothetical, optimistic estimate, of a group of humans that make no mistakes.
If you want to appreciate it, you can try the task yourself here: http://cs.stanford.edu/people/karpathy/ilsvrc/
Here is the guy who tried to get his own accuracy on imagenet: https://karpathy.github.io/2014/09/02/what-i-learned-from-competing-against-a-convnet-on-imagenet/
Getting 5.1% error was really hard, takes a lot of time to get familiar with the classes and to sort through reference images. The 3% error was an entirely hypothetical, optimistic estimate, of a group of humans that make no mistakes.
If you want to appreciate it, you can try the task yourself here: http://cs.stanford.edu/people/karpathy/ilsvrc/