Penfield Mood Organs are devices used by future citizens to regulate their emotions. (But does it come in chewable tablets?) All they have to do is find the proper emotion number in the manual, dial it, and then they get to feel whatever they want. For example, if they input 481, they instantly receive an "'[a]wareness of the manifold possibilities open to [them] in the future'" (1.19).
Just imagine plugging an emoticon into a device and instantly feeling :-), :-o, :'(, or even :-P. That's some pretty sweet technology—even if there's an irony underlining the whole affair that's just a tad disturbing.
Basically, the Penfield mood organ turns people into machines, programming them like one might a computer or, yep, an android. Iran makes this exact comparison:
"My first reaction consisted of being grateful that we could afford a Penfield mood organ. But then I realized how unhealthy it was, sensing the absence of life, not just in this building but everywhere, and not reacting—do you see? I guess you don't. But that used to be considered a sign of mental illness; they called it 'absence of appropriate affect.'" (1.17).
The problem with the Penfield, according to Iran, is that people live with the absence of appropriate affect. Also known as the flat affect, this is the condition where "a person does not display emotions to the degree that other members of his or her culture normally exhibit" (source). For example, if a future citizen gets fired they don't have to feel sad about it. They can jump on the Penfield and, bam, instant elation! Now legal in 23 states!
But remember how one of an android's key characteristics is that they do not feel empathy when, say, they see an animal being tortured? Androids suffer from the flat affect, just like users of the Penfield mood organ. But don't see Penfield users with bounties on their heads, do you?