ISTR it being suggested that intermittent positive reinforcement (IPR) forms the basis of a model for gambling addiction. Some research has shown that when positive reinforcement for a behavior is delivered irregularly/inconsistently, the behavior is elicited even more strongly than when consistent positive reinforcement is used. Indeed, I’ve seen videos of research monkeys banging away furiously at a button, with the button having been programed to deliver a morsel of food only about 10% of the time. Gambling may be seen the same way: only a fraction of those scratch-off lottery tickets are winners, for example, but addicts will still buy them by the dozens.
If IPR is at work here, then clearly our ingrained response to IPR is maladaptive in this situation. Is there a circumstance in which our ingrained response to IPR is adaptive, i.e. responding vigorously to IPR helps to perpetuate the species and/or the individual’s genes?
The initial question you pose in the thread title is answered by yourself. Good answer!
The second question, I guess, is the real question. And the answer to that is ‘yes,’ IPR is a good survival instinct for all animals. It’s the mechanism by which you start to figure out how the world works. If you look under a rock and there are tasty grubs there, then, quick! look under all rocks! But not all rocks have grubs. So you keep trying even if some rocks don’t pay off, but that’s OK, because there is enough of a pay-off from trying all rocks. And hey, maybe after a while you notice that only rocks that are likely to have cool, moist, and loose soil underneath are the ones that have the grubs. You wouldn’t have noticed that unless you kept trying all the rocks.
But that just explains why persistence is selected for. It doesn’t explain why we look under rocks MORE if there are only grubs 10% of the time than if there are grubs every single time. Though I suppose it’s more like “We get into looking under rocks MORE if there is a pile of 10 grubs 10% of the time than if there is one grub every single time”. What would be interesting to know is if IPR is stronger than consistent reinforcement even when the average payout is lower: would we rather find 10 grubs 10% of the time or 2 grubs every time?
I, myself, am not a fan of evolutionary biology except in the most obvious cases: I think it’s too easy to construct “just so stories” that work because we are starting from the conclusion and working backward.
Positive Reinforcement is subject to habituation - a declining response to stimulus. Over time, you need to provide more stimulation to elicit a response. In terms of brain chemistry, this is mediated by the dopamine response. IPR has a re-excitation effect, effectively “resetting” the threshold as a reaction to failure (and even enhancing the positive response if the run of negative responses is large). So the dopamine “high” of success in IPR is much higher than that involved when PR brings success. But the “lows” associated with IPR are also lower, but may be forgotten faster. IPR creates a boom/bust pattern, whereas PR is more stable but at a lower level of perceived reward.
In real world terms, it is more likely that you have to turn over a lot of rocks before you find a grub. So nature itself selects for IPR - it is adaptive to our environment and helped humans (and other animals) become successful across a wide range of ecosystems.
It is also worth noting that interfering with the human dopamine system (drugs such as Miraplex, used to treat Parkinsons disease) can also trigger compulsive risky behaviour (gambling addiction, obsessive eating and various sexually related addictions including paedophilia).
My guess would be that we posess a gene for persistence that we may use in hunting, fishing and breeding. If we got discouraged easily fishing we may starve to death. The occassional fish gives us a huge rush and even though it may take hours or even days sometimes for another fish we happily pursue it. Similar with hunting especially with primitive weapons, we may have to take 5 shots to get one animal. Pursuing a mate is another example, we may flirt, dance, smile at whatever a dozen or so ladies before we find one that responds. The one that does respond reinforces the behavior. I see a definite advantage to the addictive behavior here.
Their may be something else at work also, when we gamble we often develop strategies. The same thing when we hunt, fish or turn over rocks, or hunt for mates. When we change a strategy we persist to validate our own thought process to some extent.
Because IPR developed in our ancestors before we were able to do math. And even then, there are many aspects of probabilities which are non- and counter-intuitive even for us humans (e.g., plane travel is statistical safer than car travel, yet, which one is thought of as being more dangerous?). So, yes, we can figure out that there are grubs under only 10% of all rocks, and therefore, if we want to survive, we have to overturn 235 rocks per day. But for our ancestors, they couldn’t make that calculation. The ones who got the dopamine rush for a random success (grubs!) went chasing after more rocks than those who didn’t and thus survived better passing on that trait to their young.
I suspect their may be another factor involved where those who get addicted to gambling may be lacking sufficient dopamine stimulus in other healthier areas of their lives. Once they discover they can get it gambling they don’t look back. Their is probably a genetic advantage to this as well as if we are not good at one thing we will keep looking until we find something that satisfies us.
My WAG:
If there are always grubs under every rock, then there’s no real scarcity. You can spend half the day snipe hunting and know that dinner is still there under the rock if it doesn’t pan out.
When there is scarcity or unpredictability of grubs, you work hard to maximize that resource while it’s still available; you can go back to snipe hunting after you’ve used up the grubs. In nature, where things tend to be limited and seasonal, it makes sense to take advantage of the limited resources first, then fall back on the more predictable resources later. If the resource truly is seasonal, then you quickly reach a point where there are no more grubs at all, and the behavior is no longer intermittently reinforced and you stop.
So gambling makes this maladaptive because gambling is such an artificial construct. It’s designed so that the occasional rewards are interspersed with small losses, and it takes a real analysis to see just how much you’re losing. There’s just enough strategy to make you think you can beat the system, but just enough complexity to prevent you from understanding why you can’t beat it. You’re certainly not going to see a scenario like that very often in nature.
when I was a kid I would spend my days hunting for lizards, snakes, salamanders, shrews things like that by turning over rocks and boards in local fields. I was hopelessly addicted and would sometimes ditch school so I could turn over rocks. The most common animal was an aligator lizard and the least common were king snakes. I might only have caught a couple of snakes in a year. The rush of knowing I might catch a snake was about like getting a royal flush. I have since identified myself as having an addictive personality but only excersize it on my hobbies. The hobbies have the same identifiable super reward that I only achieve on occassion but that seems to be enough to keep me sucked in and I can see where the persistance gene is connected to the chemical rush I get when I am successful.
Is there a similar evolutionary basis for all kinds of addiction? In some families I know, there are siblings who variously have alcohol addiction, gambling addiction, and nicotine addiction (fortunately no drugs). Does the pattern of addiction run in families, and each person has to find their own way to get addicted?
At the heart of all addictions is the dopamine response - the way we respond to feeling good. Physical addiction (like nicotine) sits on top of this response. For many people, success at beating one addiction comes with the risk of another - a proportion of patients who have successful bariatric surgery leading to weight loss may develop other addictions (alcohol, nicotine, gambling). I just read an article the other day about a drug addict who had beaten his drug addictions, but was compulsively running 20+ miles a day - one addiction traded for another (admittedly a healthier one, but possibly not sustainable).
So it is likely that some aspects of this response are genetic. However, some is conditioned and there also may be environmental/biochemical factors - a proportion of children respond badly to stress, for example (so-called orchid children), and may be more prone to addictive behaviour that would not occur if they had grown up in a nurturing environment. More resilient children (dandelion children) are not as damaged by stress in childhood, but (as I recall) showed similar rates of addictive behaviour whether they had a stressful or nurturing childhood.
Perhaps the question can divided into two sections:
Why (from an evolutionary biology POV) is some level of randomnly intermittent positive reinfocement such a strong stimulus to maintain a learned behavior?
Why in some percent of the population does that play out as compulsive gambling, in behaviors that persist despite the reinforcer being extremely intermittent?
The first is fairly well addressed already it seems. Persistence pays off and is more needed when the pay-offs are scarce but highly valued. No persistence is required when any effort leads to a result.
But why does such a response play out in maladaptive ways in a certain segment of the population? Is it that some have an excessive load of the genes that contribute to the behaviors? Or would the level these people have actually be adaptive if manifest in an environment more similar to that which was present for most of the time scale meaningful from an evolutionary selective perspective?
