SIHM: Why Do We Dream?

There are many ways to answer this question. Most answers I've seen, from various fields from neuroscience to psychoanalysis to common, address some part of the functions of dreams and contain a good deal of truth. What we lack at the moment is a coherent theory as to why it is necessary, especially in the form it exists. What would we not be able to do if we didn't dream at all? What would we not be able to do if we dreamed differently?

As explained in a previous post - Structure and Interpretation of Human Minds - the tasks that the mind has to perform for us to even deal with the basic everyday life are rather overwhelming in scope. At the immediate level, it has to process sensory information and respond in real time. In order to respond properly it needs an elaborate model of reality.

The Structure of Reality

What we commonly call "reality" in conversations is what I refer to as a model of reality - or some common subset (or sometimes a superset) of such models within some population. For instance, I may say that Peter the Great was a real person, or in a more convoluted way, that the historical existence of Peter the Great is part of reality. What we're saying is that we have accepted as part of our model of reality that he existed in the form we have generally modeled him through our common imagination. The earth rotating around the sun, various physical laws, etc, are all aspects of our model of reality, aspects that are accepted by a large percentage of the human population.

But not all modeling happens in the form of strict propositional truths. Ultimately, what's more important than modeling the world propositionally (by encoding reality as a series of factual propositions) is mapping situations to reactions. Propositional truths, at best, can be seen as a tool that helps accomplish this mapping more efficiently. While simpler cognitive systems (many animals, many computer programs, etc) can be wired to react to specific stimuli, the cognitive problems we deal with are far too complicated without using propositional truths. It is because our modeling has reached this level of sophistication that we have a concept of reality.

Then, our model of reality can be seen as some sort of computational network populated by a large number of heuristics, some of which encode propositional truths and others code for reactions to situations. One important point from my earlier post Structure and Interpretation of Human Minds was that the mind does not clearly separate propositional truths from behavioral heuristics and all sorts of random heuristics get encoded as truths as long as they support seemingly advantageous behavior. These are, in some sense, indistinguishable from other propositional truths. In fact, all propositional truths are encoded as such ultimately for this reason - it's just that we do enjoy being right and/or being confirmed by others. Thus in domains where other emotional forces are weak, our model of reality tends towards truths that are verifiable by others as such.

One may ask, at this point, how does this model of reality in terms of these heuristics encoding truths and situational behavior - let's call those rules - get used? Let's take an example of someone driving. The driver has to be constantly aware of the causal consequences of his own actions. He has to know what the gas pedal does and what the steering wheel does. He also needs to predict how other cars will move, based on his experience, based on his knowledge of the traffic signals, etc. These rules combine to give him a sense what is likely to happen - they limit the range of possibilities his mind must consider in real time. Then the rules that govern his behavior kick in to guide his actions towards more positive possibilities. Note that deciding to pay attention or spend time thinking about something itself is immediate reaction that needs to be learned. He cannot afford to figure out, when he's about to run over a pedestrian, how much time he has to consider what to do. He must react, and he must have already known that's what he needs to do. On the whole, those rules code for the range of possible future situations at any given moment (in other words, cause and effect or how events progress over time which is why causality is such a significant part of our model of reality, despite poor logical justifications for it) and proper reactions (in some cases it could just be deliberation - you may not have already the answer to some math problem seen during a test, but at least you know what do) to them. This is, effectively, reality.

Reality and Dreams

What does any of this have to do with dreams? My contention is that dreams make all of this possible. What's even more overwhelming than the number of rules that constrain possibilities is the sheer range of possibilities before applying the rules. The rules we use to generate possible realities in our mind must both be sufficiently narrow to exclude outrageous ones (which allows for faster reaction and a lighter cognitive load) yet not neglect even unlikely possibilities that have significant damage potential. Having a wrong set of rules could be disastrous - the driver may not see that the truck coming his way is on a collision course, or that a toddler is not looking his way and won't get out of the way. Yet, from a computational standpoint, sometimes the only way one can tell if one rule is better than another is to try out both on some level. This is where dreams come in - dreams provide a safe testing ground for new rules. Thus it is during dreams where we figure out what reality is. We make up all kinds of alternate rules for reality (how things are) and for behavior (how we should respond), and figure out which ones make sense and which ones don't. To some extent, daydreaming (or thinking to a lesser extent) serves a similar purpose, except that some rules are difficult to train under this scenario, since the mind must perform a lot of other cognitive tasks when awake - this increases the possibility of inappropriate or even dangerous reactions (or non-reactions) to external stimuli. If your imagination is too vivid, you may not be able to respond properly to physical stimuli; if your imagination is not vivid enough, you're not able to train certain rules or consider larger changes in the rule set. Those with schizophrenia, for instance, appear to daydream in an uncontrollable manner with nearly the same level of vividness as others dream at night. Part of the rigidity of human sleeping/dreaming patterns, some of which may seem computationally inefficient probably has to do with the extreme difficulty of determining the meta-rule that determines when it's okay to dream - it's difficult to simulate the effects of dreaming itself within a dream. One speculative hypothesis I have is that at least some cases of mental illness may be caused by irreversible meta-training of the process of dreaming itself - it may allow the entire computational stage for determining reality to be hijacked by a narrow emotional need.

Other thoughts

I've recently heard the Jessica Alba refutation to a related general hypothesis that dreams serve an active cognitive purpose. It goes like, if dreams help you prepare for reality, why do I have a threesome involving Jessica Alba and Snow White in my dreams, like I need to prepare for that possibility? This refutation directly supports my hypothesis. You know it's ridiculous precisely because you have dreams along that line. Our rules for figuring out what's absurd or not must be developed as well. For nearly any absurd dream, you can probably find a mentally ill person who believes in a similarly absurd reality. If you don't take for granted that you know the difference between real and absurd, learning what's absurd requires simulating absurd scenarios, at least in some cases.

Beyond absurdity, the other common theme in dreams is threats. This is also expected by the hypothesis. Reality needs to be most precisely modeled (and our responses most intensely rehearsed) in potential situations where significant action is required and incorrect action is costly. Thus the mind is biased to remember and generate rules based on emotionally intense scenarios.

What I have not attempted to explain is why we remember some dreams but not others (most) - most likely this has no clear computational purpose; remembering dreams is likely one of those slightly incomplete adaptations that do not have significant adverse effects and thus remained. Again, because of the difficulty of meta-training of the process of dreaming itself, a lot of the specific mechanisms of dreaming, other than the requirement that the mind not have to perform any significant cognitive task at the same time, are probably not particularly adaptive, merely not dramatically maladaptive.

Structure and Interpretation of Human Minds

In an earlier post, I explained that cognition is best understood as interaction between mental processes. Here, I explain the nature of some of those higher-level mental processes and the interaction and relationships among them. Some of those explanations are, in many ways, simply rewording of some obvious things we already know about the human mind. Others are speculative hypotheses.

Before discussing how the human mind works, we can consider what it must do. Here are some broader classes of computational tasks that our mind performs:

• Modeling natural phenomena - the mind must model the physical world.


• Modeling social phenomena - the mind must model the social structure, including self, others and any interaction amongst them.


• Establish preferences and actions to perform - the mind must somehow learn to know what to like, what not to like, what to do and what not to do.


• Allocate resources among various processes - the mind must allocate its limited resources using some control structure At any point in time, there are many things we want to do that cannot be performed simultaneously - the mind must prioritize between these tasks. Furthermore, the mind must decide what to think about, as well as what to pay attention to.

Of those computational tasks, modeling of the social structure and resource allocation using a control structure are intertwined in an interesting way. Undoubtedly, one's comprehension of the social structure must be taken into account in the way the mind prioritizes the tasks. For example, consider a soldier. The military command hierarchy largely dictates the decisions he makes. He may have his own preferences regarding what to do, but when he receives an order from his superior, that is what he must do - it overrides his other personal preferences. While it's tempting to use a generic decision-making framework where the mind does a global cost-benefit analysis before making decisions, soldiers obeying orders do not first question orders, evaluate the pros and cons and act accordingly - they instinctively obey orders. Remember that whether to do a cost-benefit analysis itself is a decision, as well as deciding how much time and cognitive resoures to spend on the analysis. But many decisions must be made in real time - a soldier must choose between retreating and saving a comrade's life and may not have more than a fraction of a second to decide. By the same token, we follow social conventions every second of our life, without having the luxury to question or scrutinze individual decisions. When a mother with two kids gets on a subway train, she has to balance her own needs with the kids' needs and other passengers' needs. She must pay attention to many things, including potential threats and her kids' behavior.

While in the soldier example, the control structure is about doing what one is told, the control structure here is much more nuanced - it's about attention and more subtle social obligations. The mother knows what her obligations, to herself, her kids and other passengers, as dictated by the social structure are and her attentional resources are divided accordingly. Should any emergency or any other situations requiring decisions arise, she'll know what to do - there would no particular need for her to perform a cost-benefit analysis. Notice, for instance, that when you're on a train (and are not the mother), you also pay more attention to the kids than to adults. In fact, one would notice that the amount of positive attention you pay to someone is (let's ignore for time being how we can't help but pay attention to homeless people who smell and other factors that demand our attention) highly correlated with the degree to which you would be socially obligated to help the person in an emergency.

So what does this all mean? The control structure is some sort of a global process. Our mental representation of the social structure, likewise, is a group of interacting processes. We must model each person in our social network, consider the relationship between the person and self and the variety of rules, written, unwritten, real and imaginary by which this relationship is governed. To the extent that the control structure, even at the most subtle level, takes into account this social structure, the group of interacting processes that model the social structure effectively controls the control structure, which is another way of saying that those processes form part of the control structure (control over control is control). Thus, the processes that model the social structure (with all the subtle social rules that detail our obligations under a variety of scenarios, many of which never come to pass) partially governs the mind. Thus, in this sense, the mind's internal system of control, mirrors the subtle control structure inherent in the society's rules and obligations.

Where does the rest of the control come from? Self, of course. Everyone has basic needs and desires. Though many things that we think of as our own desires are a combination of our desires and social conventions. We don't generally desire nice clothes for ourselves at first - we want to look nice to others. This is where preference learning comes from - not only are we explicitly influenced by what we've learned as other's preferences and take those into account, we learn to incorporate those preferences as our own. Over time, means become an end. Note that this preference learning process is effectively a form of precomputation (though all learning, on some level is). By incorporating what others want and wanting it yourself, you can skip the process of having to model. At the same time, complex behavior cannot easily be modeled as preferences. In fact, even something as simple as eating vegetables, which should be modelable as such, often isn't. Many carry an aversion to healthy foods well into their adult life and learn to eat vegetables not as a matter of preference for its taste, but as some sort of obligation to self.

Thus precomputation of socially desirable behavior as preference has limits - this does not mean that other forms of precomputation aren't possible. As mentioned before, we often tend to just know what to do in fairly novel situations that we've never been in before. It can also be critical for the mind to partially precompute decisions that need to be made under infrequent emergencies - those are the precise situations where one can't afford to leisurely consider various possibilities. This is where our modeling of natural phenomena and social phenomena comes in - in order for us to quickly respond in situations of importance, we're constantly using our models of reality to simulate reality (this encompasses imagining, daydreaming, nightdreaming and plain-old thinking - it can be done consciously or not, while sleeping or awake) in our mind. This computation can be seen as training of the control structure using the model of social and natural reality, but it can also be see as training of all of those. Some faults or incongruity in our understanding of reality can certainly be resolved by elaborate simulations.

All of this suggests some kind of correspondence between the structure of a society and the structure of a mind. To the extent that we simulate the social reality in our mind to make decisions, the social reality, or at least some virtual model thereof, drives our decision making proces - in fact this simulation process is largely the hypothetical control structure we were speaking of earlier. Furthermore, the feedback goes back the other way - to the extent that we, then, interact with others using results derived from our model, social interaction is borne out of our mental model of social reality.

On some level, everything in this post is a fairly obvious observation regarding our mind presented in a somewhat unconventional framework. Yet, this correspondence between society and mind has profound implications regarding our ability to study the human mind as a computational system. It's difficult to study how a mind functions because we have no inherent ability to interpret what's going on inside. As argued here before, neurological studies tend to be fruitless in understanding higher level functions because there are simply too many abstraction layers. However, understanding the nature of correspondence between a social structure and a mind may allow us to see, on a higher level, how the mind functions internally - after all we can directly observe many aspects of social interaction. Furthermore, we can apply some principles of computation, especially with the understanding that the system must have evolved and with some guesses regarding specific selective pressures it evolved under.

For instance, because the process of reality simulation is crucial to the control structure, we seem to use it not merely to simulate possible realities, but rather to manipulate the process itself to get ourselves to do things that some part of our mind thinks is a good idea. One good example is that some people imagine their deceased parents when they want to do the right thing. It's not that their deceased parents are a relevant part of social reality but rather that thinking of them is a way the mind came up to help make certain decisions. This sort of exaptation, where features that evolved for one reason are co-opted for another, is a common theme in evolution. My hypothesis is that many goal-driven processes in our mind (any desires, wants, etc) are constantly hijacking this largely subconscious reality simulation process in order to pursue their own agenda. Once the reality simulation becomes an important part of the decision making process, this sort of hijacking is nearly inevitable. Thus the reality simulation process, which can be seen as a complex network of processes that represent elements of social reality (such as mental model of others that are socially relevant) must also deal with various mental processes that aren't necessarily modeling any external reality, but rather elements of desires. This answers a question from earlier: how do we balance the needs of self with the needs of others? - we allow the needs of self to hijack our model of how we should behave. This is why, despite being incredibly social aware, we're still a bit self-centered - if there was no such hijacking, we'd perceive reality in a neutral way and act as though our needs were no more important than those of others.

This hijacking also explains the phenomenon of wishful thinking - if wishes or desires are hijacking the process of simulating reality which helps us clarify what reality is, it's no surprise that some aspect of what we want appears to be part of reality, because we can't necessarily figure out whether something appears in the simulation because it's an aspect of reality or because it was inserted by our desires.

It appears, then, that we're powerless against our own desires manipulating this reality simulation process. But we already have methods for dealing with other processes. If we can imagine our mother telling us what to do in this reality simulation process, we also need to, if necessary, tell her, hopefully in some polite way, to shut up so that we can do other things instead. How we imagine we would interact with others in this reality simulation process is how we govern mental processes representing our models of others. It's imagination in the sense that you're not actually interacting with others, but it's real in the sense that you're actually interacting with those mental processes. Of course, this general methodology cannot be too far from how you interact with others, because if that's the case, you're no longer simulating reality, but fantasies. While some fantasies may be mentally healthy, we do need to model at least some part of reality to make reasonable decisions. Anyway, when the desires intrude upon this reality simulation process, we are likely to use a mechanism we already have to govern them - the same used for governing mental processes representing others. Thus how we govern our mind, all those conflicting desires and wants, is largely reflective of how we imagine we would govern others, which in turn reflects how we actually interact with others. This neatly explains megalomania - governing your own desires is genuinely difficult and one way to do it is by giving a lot of power to self in the reality simulation process. Unfortunately, while this can be useful for governing inner desires, it necessarily leads to a distorted view of self in relations to others and affects social interactions accordingly.