Valuing Sentience: Can They Suffer?

In the re­cent dis­cus­sions here about the value of an­i­mals sev­eral peo­ple have ar­gued that what mat­ters is “sen­tience”, or the abil­ity to feel. This goes back to at least Ben­tham with “The ques­tion is not, Can they rea­son? nor, Can they talk? but, Can they suffer?”

Is “can they feel pain” or “can they feel plea­sure” re­ally the right ques­tion, though? Let’s say we re­search the biolog­i­cal cor­re­lates of plea­sure un­til we un­der­stand how to make a com­pact and effi­cient net­work of neu­rons that con­stantly ex­pe­riences max­i­mum plea­sure. Be­cause we’ve thrown out nearly ev­ery­thing else a brain does, this has the po­ten­tial for or­ders of mag­ni­tude more sen­tience per gram of neu­rons than any­thing cur­rently ex­ist­ing. A group of al­tru­ists in­tend to cre­ate a “happy neu­ron farm” of these: is this valuable? How valuable?

(Or say a su­pervillian is cre­at­ing a “sad neu­ron farm”. How im­por­tant is it that we stop them? Does it mat­ter at all?)