Many people, including Geoffrey Hinton, have raised concerns about the back-propagation algorithm and the fact that it’s likely not a promising way to achieve Artificial Intelligence (see this Axios blog post).
Alternative mechanisms for learning have been and are currently studied to try and approach the learning problem in a more effective way.
Direct feedback alignment
The theory is sometimes summarized as “Cells that fire together wire together.”.
- Arild Nøkland. . "Direct Feedback Alignment Provides Learning in Deep Neural Networks". Arxiv:1609.01596 [cs, Stat]. http://arxiv.org/abs/1609.01596.
- James C. R. Whittington, Rafal Bogacz. . "An Approximation of the Error Backpropagation Algorithm in a Predictive Coding Network with Local Hebbian Synaptic Plasticity". Neural Computation 29 (5):1229–62. DOI.
- Beren Millidge, Alexander Tschantz, Christopher L. Buckley. . "Predictive Coding Approximates Backprop Along Arbitrary Computation Graphs". Arxiv:2006.04182 [cs]. http://arxiv.org/abs/2006.04182.