Thanks for the feedback!
The reference to linear algebra should only show, that there have to be states which are mapped to similar representations, even if we don't know a priory which ones will be correlated.
But if we now look closer at the structure of the brain as a neural network and the learning mechanisms involved, then I think that we could expect positive concepts to be correlated by cross activation, as you explained.
The point of the article is not to come up with a perfect explanation for how the halo effect is actually caused, but to show that there doesn't have to be an evolutionary reason for it to evolve, besides the 'obvious' one that pwno mentions in his comment.
Yes. I thought you were making an interesting and useful point. I was offering you an alternate formalism to explain the phenomenon, not expressing a disagreement with anything you wrote.
Introduction
When people on LW want to explain a bias, they often turn to Evolutionary psychology. For example, Lukeprog writes
I think that ''evolved faulty thinking processes'' is the wrong way to look at it and I will argue that some biases are the consequence of structural properties of the brain, which 'cannot' be affected by evolution.
Brain structure and the halo effect
I want to introduce a simple model, which relates the halo effect to a structural property of the brain. My hope is that this approach will be useful to understand the halo effect more systematically and shows that thinking in evolutionary terms is not always the best way to think about certain biases.
One crucial property of the brain is that it has to map a (essentially infinite) high-dimensional reality onto a finite low-dimensional internal representation. (If you know some Linear Algebra, you can think of this as a projection from a high-dimensional space into a low-dimensional space.) This is done more or less automatically by the limitation of our senses and brain's structure as a neural network.
An immediate consequence of this observation is that there will be many states of the world, which are mapped to an almost identical inner representation. In terms of computational efficiency it makes sense to use overlapping set of neurons with similar activation level to represent similar concepts. (This is also a consequence of how the brain actually builds representations from sense inputs.)
Now compare this to the following passage from here.
This shouldn't be a surprise, since 'positive' ('feels good') seems to be one of the evolutionary hard-wired concepts. Other concepts that we acquire during our life and associate with positive emotions, like kindness and honesty are mapped to 'nearby' neural structures. When one of those mental structures is activated, the 'closed ones' will be activated to a certain degree as well.
Since we differentiate concepts more when we are learning about a subject, the above reasoning should imply that children and people with less education in a certain area should be more influenced by this (generalized) halo effect in that area.
Conclusion
Since evolution can only modify the existing brain structure but cannot get away from the neural network 'design', the halo effect is a necessary by-product of human thinking. But the degree of 'throwing things in one pot' will depend on how much we learn about those things and increase our representation dimensionality.
My hope is that we can relief evolution from the burden of having to explain so many things and focus more on structural explanations, which provide a working model for possible applications and a better understanding.
PS: I am always grateful for feedback!