What neuroscience too often neglects: Behavior

A Quora conversation led me to recent paper in Neuron that highlights a very important problem with a lot of neuroscience research: there is insufficient attention paid to the careful analysis of behavior. The paper is not quite a call to return to behaviorism, but it is an invitation to consider that the pendulum has swing too far in the opposite direction, towards ‘blind’ searches for neural correlates. The paper is a wonderful big picture critique, so I’d like to just share some excerpts.

neurobehav_krakauer_etal_poeppel2017

“Neuroscience is replete with cases that illustrate the fundamental epistemological difficulty of deriving processes from processors. For example, in the case of the roundworm (Caenorhabditis elegans), we know the genome, the cell types, and the connectome—every cell and its connections (Bargmann, 1998; White et al., 1986). Despite this wealth of knowledge, our understanding of how all this structure maps onto the worm’s behavior remains frustratingly incomplete.”

“New technologies have enabled the acquisition of massive and intricate datasets, and the means to analyze them have become concomitantly more complex. This in turn has led to a need for experts in computation and data analysis, with a reduced emphasis on organismal-level thinkers who develop detailed functional analyses of behavior, its developmental trajectory,and its evolutionary basis. Deep and thorny questions like‘‘what would even count as an explanation in this context,’’ ‘‘what is a mechanism for the behavior we are trying to understand,’’and ‘‘what does it mean to understand the brain’’ get sidelined. The emphasis in neuroscience has transitioned fromthese larger scope questions to the development of technologies,model systems, and the approaches needed to analyze the deluge of data they produce. Technique-driven neuroscience could be considered an example of what is known as the substitution bias: ‘‘[.] when faced with a difficult question, weoften answer an easier one instead, usually without noticing the substitution’’ (Kahneman, 2011, p. 12).”

This next excerpt raises an important issue with interpretations of mirror neuron studies. (I also have my own little rant about mirror neuron “theory”.)
“Interpretation then has the following logic: as neurons can be decoded for intention in the first person, and these same neurons decoded for the same intention in the third person, then activation of the mirror neurons can be interpreted as meaning that the primate has understood the intention of the primate it is watching. The problem with this attempt to posit an algorithm for ‘‘understanding’’ based on neuronal responses is that no independent behavioral experiment is done to show evidence that any kind of understanding is actually occurring, understanding that could then be correlated with the mirror neurons. This is a key error in our view: behavior is used to drive neuronal activity but no either/ or behavioral hypothesis is being tested per se. Thus, an interpretation is being mistaken for a result; namely, that the mirror neurons understand the other individual.”

Here the authors talk about the importance of emergence as a bridge between neurons and behavior:

“The phenomenon at issue here, when making a case for recording from populations of neurons or characterizing whole networks, is emergence—neurons in their aggregate organization cause effects that are not apparent in any single neuron. Following this logic, however, leads to the conclusion that behavior itself is emergent from aggregated neural circuits and therefore should also be studied in its own right. An example of an emergent behavior that can only be understood at the algorithmic level, which in turn can only be determined by studying the emergent behavior itself, is flocking in birds. First one has to observe the behavior and then one can begin to test simple rules that will lead to reproduction of the behavior, in this case best done through simulation. The rules are simple—for example, one of them is ‘‘steer to average heading of neighbors’’ (Reynolds, 1987). Clearly, observing or dissecting an individual bird, or even several birds could never derive such a rule. Substitute flocking with a behavior like reaching, and birds for neurons, and it becomes clear how adopting an overly reductionist approach can hinder understanding.”

Krakauer, John W., Asif A. Ghazanfar, Alex Gomez-Marin, Malcolm A. MacIver, and David Poeppel. “Neuroscience needs behavior: correcting a reductionist Bias.” Neuron 93, no. 3 (2017): 480-490. [Paywalled]


My main criticism of this paper might be that their proposed solution — a separation between analysis of behavior and analysis of neural data, with behavioral analysis ideally happening first — might be too rigid, and also might leave the behavioral analysis somewhat underconstrained. It is definitely important to have a clear behavioral hypothesis if you are running a behavioral study, even if is part of a larger study of neural data. But the actual process of understanding might require a lot more ‘cross-talk’. It may not always be useful to come up with a high-level analysis of behavior in isolation from neural data. There is no guarantee that the high-level analysis will be accurate: there may be multiple high level models that correspond to the same behavioral data. So we might need to add a third circle to their Figure 1: one for the space of behavioral explanations.

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Could the brain be a radio for receiving consciousness?

 

bradio.pngHere’s an answer I wrote a while ago to the following question:

 Is there any conclusive proof that the brain produces consciousness? What rules out the case that brain acts as receptor antennae for consciousness?

This is actually a fun question! Taken in the right spirit, it can be a good way to learn about what science is, and also what the limitations of science are.

What would count as proof that the brain produces consciousness? In the future we might try an experiment like this: we build an artificial brain. Let’s say we can all agree that it exhibits consciousness (leaving aside for now the extremely tricky question of what the word “consciousness” even means). Would this prove that the brain “produced” consciousness? Maybe.

But maybe the brain-as-antenna crowd would claim that their favored hypothesis hasn’t been ruled out. After all, if consciousness is somehow floating in the ether, how could we be sure that our artificial brain wasn’t just tuned to the ‘consciousness frequency’, like a gooey pink radio?

We’d need to construct some kind of cosmic-consciousness-blocking material, and then line the walls of our laboratory with it. Then we’d be able to decide on the question one way or the other! If our artificial brain showed no signs of consciousness, the antenna crowd could claim victory, and say “See!, you need cosmic consciousness in order to get biological consciousness! Consciousness is like yogurt: if you have some you can always make more.”

Constructing an artificial brain is hard enough. We have no idea if we will ever have enough understanding of neuroscience to do so. But constructing a consciousness-shield is straight out of science fiction, and just sounds absurd.


In any case, there’s actually a much bigger problem facing any scientific approach to consciousness. No one has any idea what consciousness is. Sure, there’s plenty of philosophical speculation and mystical musing, but in my opinion there’s almost nothing solid from a scientific perspective.

Here’s why I think science cannot ever address the subject of consciousness: science studies objectively observable phenomena, whereas the most crucial aspect of consciousness is only subjectively observable. What are objectively observable phenomena? They’re the ones that more than one person can observe and communicate about. Through communication, they can agree on their properties. So the word “inter-subjective” is a pretty good synonym for “objective”. Objectivity is what can be agreed upon by multiple subjective perspectives.

So the sun is a pretty objective feature of reality. We can point to it, talk about it, and make measurements about it that can be corroborated by independent groups of people.

But consciousness is not objective in the same way that the sun is. I do not observe anyone else’s consciousness. All I observe are physical perceptions: the sights and sounds and smells and textures associated with bodies. From these perceptions I build up a picture of the behavior of an organism, and from the behavior I infer things about the organism’s state of mind or consciousness. The only consciousness I have direct experience of is my own. And even my own consciousness is mysterious. I do not necessarily observe my consciousness. I observe with my consciousness. Consciousness is the medium for observation, but it not necessarily a target of observation.

Clearly all the scientists who claim to study consciousness would disagree with my perspective. Their approach is to take some observable phenomenon — either behavior or some neural signal — and define it as the hallmark of consciousness. There’s nothing wrong with defining consciousness as you see fit, but you can never be completely sure if your explicit definition lines up with all your intuitions about the boundary between conscious and non-conscious.

For example, Information Integration Theory (IIT) proposes that there is a quantity called phi (which at the current historical juncture appears impossible to compute) that captures the degree of consciousness in a system. Armed with this kind of theory, it is possible to argue* that extended, abstract entities — such as the United States as a whole — are conscious. Some people like this generous approach. Why lock up consciousness in skulls? The proponents of IIT have gone so far as to claim that they are okay with panpsychism: the idea that everything from quarks to quasars is at least a little bit conscious.

If everything is conscious, then the question of whether the brain “produces” consciousness — or the universe “transmits” it — becomes moot. There is no ‘problem of consciousness’, since it’s already everywhere.

Neuroscientists like me will probably still have jobs even if society decides to bite the panpsychist bullet. We have other things to worry about beyond consciousness. In fact many of us are actively uninterested in talking about consciousness — we call it “the c-word”. We’re happy to just study behavior in all its objectively observable glory, and hope to understand how the brain produces that. Whether and where exactly consciousness arises during this process seems like a question we can leave unanswered for a generation or two (while enjoying the various after-work conversations about it, of course!). For now we can focus on how our gooey pink radios give rise to language, or memory, or emotion, or even the basic control of muscles.


Notes

* Philosopher Eric Schwitzgebel wrote a very interesting essay entitled ‘If Materialism Is True, the United States Is Probably Conscious’.

More on the dreaded c-word!

Here are some consciousness-related answers that may be of interest:

How does the brain create consciousness?

What percent chance is there that whole brain emulation or mind uploading to a neural prosthetic will be feasible by 2048? [I’ve posted this one on this blog too.]

What are some of the current neuroscientific theories of consciousness?

What do neuroscientists think of the philosopher David Chalmers?

Is anything real beyond our own perspective?

What is the currently best scientific answer to the psycho-physical (body-mind) question?