I wrote a paper on another experiment by Berridge reported in Zhang & Berridge (2009). Similar behavior was observed in that experiment, but the question explored was a bit different. They reported a behavioral pattern in which rats typically found moderately salty solutions appetitive and very salty solutions aversive. Put into salt deprivation, rats then found both solutions appetitive, but the salty solution less so.
They (and we) took it as given that homeostatic regulation set a ‘present value’ for salt that was dependent on the organism’s current state. However, in that model, you would think rats would most prefer the extremely salty solution. But in any state, they prefer the moderately salty solution.
In a CABN paper, we pointed out this is not explainable when salt value is determined by a single homeostatic signal, but is explainable when neuroscience about the multiple salt-related homeostatic signals is taken into account. Some fairly recent neuroscience by Oka & Lee (and some older stuff too!) is very clear about the multiple sets of pathways involved. Because there are multiple regulatory systems for salt balance, the present value of these can be summed (as in your “multi-dimensional rewards” post) to get a single value signal that tracks the motivation level of the rat for the rewards involved.
I wrote a paper on another experiment by Berridge reported in Zhang & Berridge (2009). Similar behavior was observed in that experiment, but the question explored was a bit different. They reported a behavioral pattern in which rats typically found moderately salty solutions appetitive and very salty solutions aversive. Put into salt deprivation, rats then found both solutions appetitive, but the salty solution less so.
They (and we) took it as given that homeostatic regulation set a ‘present value’ for salt that was dependent on the organism’s current state. However, in that model, you would think rats would most prefer the extremely salty solution. But in any state, they prefer the moderately salty solution.
In a CABN paper, we pointed out this is not explainable when salt value is determined by a single homeostatic signal, but is explainable when neuroscience about the multiple salt-related homeostatic signals is taken into account. Some fairly recent neuroscience by Oka & Lee (and some older stuff too!) is very clear about the multiple sets of pathways involved. Because there are multiple regulatory systems for salt balance, the present value of these can be summed (as in your “multi-dimensional rewards” post) to get a single value signal that tracks the motivation level of the rat for the rewards involved.