From a brain science perspective, the method just described is unsatisfactory because it is obvious that complex hypotheses such as crime explanations and scientific claims are not represented in the brain by single neurons. Another problem is that constraints in figure 4.2 are symmetric, allowing two elements to mutually constrain each other, so that excitatory and inhibitory links between units are also symmetric. But in real neural networks it never happens that two neurons both excite or inhibit each other. Fortunately, it is possible to model the calculation of explanatory coherence in a much more neurologically realistic way.