How effective are techniques such as biting, eye pokes, groin grabs et cetera as escapes from side control or other hold-downs? This would be in comparison to other escape methods like bridging, shrimping back to guard or a technical stand, or rolling to the knees in order to stand up.
Are those techniques which are generally illegal in grappling contexts more or less useful options than their legal counterparts? Why?
One of the major differences between the 'illegal' moves and the 'legal' moves is that the legal moves have fairly previsible responses. If you poke someone in the eye, you're not quite sure what their response will be. If you bridge, no matter the opponent's response, you're probably (no pun intended) on much more comfortable ground.
To go one step deeper - the 'legal' moves tend to be setup moves, preparing for your next moves. The illegal moves will cause physiological and abrupt reactions, which you can plan for, but can't really predict. Who knows if biting someone will make them let go or make them punch you in the temple?
So, what will be more useful to you is what you have trained for. Which probably means that, if you are training for self-defense, you should probably include the 'illegal' attacks so you are used to them, can defend against them, and can figure out when best to use them, if at all.
Assuming you have equal training in both the legal and illegal moves, then there should be no visible difference in their utility to you.
Biting is (generally speaking) a pain-compliance activity. Unless you are biting off a finger, or going for an artery, you are using your teeth as a method to induce pain in your opponent to either unbalance his technique or get him to abandon it entirely. Some other common examples include pinching and spraying people with pepper spray.
Pain is not likely to help the person feeling it be a better fighter. It can be a useful distraction from focus; but it's going to be inferior to a mechanical compliance technique.
In a life-or-death fight, I would bite any time there was something in front of my teeth for the same reasons I would use pepper spray: not because I expect it to win a fight, but because it can only reasonably serve to advantage me. It may tip the balance, though it is not reliable.
addendum to respond to follow-up below
Biting pretty much always occurs in a grapple regardless. It's when a target is close and is also relatively stationary (one does not bite a punch); but I will try to refocus my phrasing on escaping a hold and in contrast to not biting.
Mechanical escapes ("other escape techniques" in your post) are more reliable. They work unless actively countered. Biting, and all pain-compliance techniques, are less reliable used alone as they rely on someone abandoning the hold because of discomfort.
Biting during an attempt to exert a mechanical escape is more likely to improve, rather than lessen your chance of succeeding with the mechanical escape. It is a distraction to your opponent's brain as to what he is trying to do.
As to escalation: That's a pretty situational question. In competition or friendly play biting is entirely inappropriate. In a life-or-death fight, there's no where it could escalate to it isn't already at. At something in between? That seems a judgement call.
First, I see we have some definition misunderstanding.
Legal moves in terms of sport competition or self defense?
If it is self defense, you need to legitimize the level of force you use. If a bite was an available tool for you to escape and you can justify it, it was a legal move ...
Now, about biting itself.
It is a great tool if you rip a part of the opponent's flesh, and this will surely have even greater effect if you spit it out into his face, but there is a great risk in getting into contact with bodily fluids such as blood. These fluids might contain blood-borne viruses, bacterias, like Hepatitis B or C, HIV... You name it,
Would you consider to be covered with that, and have it in your mouth ?
Be safe.
The option of eye poking with your pinkies is more safer, even better with the nails.
And the legality of it: if you can justify using that level of force it is legal. Personally, if someone would hit me from behind in a dark alley I would not dwell about someone's health and safety, I could not know who, how old, and why someone did it, I would be in a position to deal with it to get away using level of the force that I perceived necessary to save my skin. Pinky eye tactics would work well. The face manipulation is well described in "Sunshido shredder", have a look.
Biting / Eye Gouging and Groin Grabbing (BEGGG) aren't in themselves escapes. You still need to know the mechanics of making some space and using it to escape. The only thing stopping you escaping is the person adapting to your escape. BEGGG could be used as a interrupt to that adaption.
Environment Conditions
Firstly I wanted to make one thing clear: you will not have a nice, clean, easy-to-drag-your-butt ground for you to use to create space: you might be wearing tighter jeans, or have a backpack, or thick winter jacket; it might be dark, wet ground, or too near a wall... This means that not always you will be able to execute the drills you have been practising, which is when you would need to count on improvisation and unpredictability.
Objective: Stand-up
Although BJJ proved to be really effective on a one to one (even "no rules" duels), on the streets the situation is very different: his friends might kick my head, he might pull a knife, the police might arrive and take us both... So the last place I want to be is scrambling on the ground with someone. Whatever escape/defense I try to pull, I will do so bearing in mind that what I ultimately want is to stand up, rather than trying to sweep him, or anything like that. I probably would not pull full guard, for instance; instead I would try and move from under the person to create space so that I can push his hips away with my feet.
Foul Techniques and Context
I would never go for a groin grab. This is small target (not bring funny) and fairly easy to protect. One of the early UFCs had an episode like that, but instead of grabbing, they were punches. He was hitting the guy right on the balls, several times; no result. Biting, yes, but it would depend on timing and context. Look at nature, how lions hunt. They run behind their preys, usually take a first bite on their backs so they can secure their claws into their preys' skin, until they climb reaching a bite to the neck.
Neck control is very important in BJJ sport because that's how you control the whole of person's body, especially if you have their hips secure as well. Plus, strong bite to the neck can be fatal. If you can get your mouth near your aggressor's neck, you can rip their throats out. What about a stone? Stones are fantastic, either if I am trying to escape and all of the sudden I see a stone lying around there that I can grab and hit him from the bottom, or even if I am on the top and I wanted to finish him (in a very extreme case, as I do have consideration for human life; but if it were a much more serious situation I would definitely make use of it). Thus, in the same way that a triangle choke is only applicable depending on timing and context the same applies for what you are calling 'foul techniques'.
Timing: When to Make Use of Foul Techniques
Another key aspect to bear in mind is timing. If we are both standing in mid-range and he is launching a double-leg takedown, I would not try to aim my finger to his eye, but counter with a punch, for example, or more likely sprawl. If he already got me on side control but not fully locked, then I would not waste my time with foul techniques, as this extra time spent in trying to poke his eye would impede me from escaping and I would end up spending more time on the ground, which is against my principle of not staying on the ground. If, on another hand, the guy got me fully locked in this position, then that's when I would do a bit of bridging, and if that was too tight, then I would probably try to reach to the next available foul technique target.
Why Bother with Foul Techniques
Because simply put, there is nothing your attacker on top cannot do while you are biting, or eye poking him that he cannot do if you were not biting him; to the contrary: the longer you stay on the bottom, the more exposed you become. I shall expand it further. Bottom Targets While you are on the bottom you might potentially be exposed to:
The attack vectors are virtually the same, whether you are biting, screaming or starting to create space to get out of the bottom - once the space has been created, then yes, his attack vectors are reduced. However, until such time, you are exposed to the same threats. What this means, essentially, is that you have a certain spectrum's width of risk (the types of attacks that can be launched against you from the top) which accommodate a certain number of escapes and counter you can perform. Adding foul techniques is an extra set of tools you could potentially add at no extra cost, meaning you are still exposed to the same threats as you would be if you had not considered foul techniques at all. So why not consider them?
Finally, as a double benefit, by incorporating these extra repertoire that most of orthodox MA trained people do not expect, you would also add the benefit of unpredictability and shock: usually under a sudden moment of surprise and shock, the natural reaction is to back away from the source of the unexpected event, which might be another window of opportunity for you to escape.
Summary
Foul Techniques are only labelled 'foul' because they are illegal in sports competition. This distinction does not exist on the streets, which is why for me they are like any other well-thought and practised technique that need to be mastered: self-preservation comes first.
Final Edit on Escalatin Issue
"Are you worried at all about potentially escalating the fight while in a disadvantageous position?"
Worrying about this would mean stop reacting in the hope that the aggressor will suddenly calm down and let go of me. In no way this is realistic. The more you comply, the harder it becomes for you to escape.
Luis Gutierrez has a nice article about the differences between street and sport martial arts:
"Just add dirt"
I can hear it now from all the street fighters... "But Luis, what about eye gouges, hair pulling, biting, ripping, pinching, scrotum striking, yanking and smashing, scratching, spitting, foaming at the mouth, growling, breaking bottles, wearing boots, colon control and crapping at will?" Well, what about all that? If you can't even hit a guy with a 16oz. glove how the hell are you going to eye jab him? If you can't keep a guy from putting you on the ground and proceeding to do his best rendition of River Dance on your cranium, how the hell are you going to just kick him in the balls or bite him? And if you indeed are getting punched, kicked, and out grappled by a superior martial artist and you get the bright idea to bite him, what's to stop him then from doing the same if not worse to you…and from a much better vantage point to boot? (Pun intended.) Bottom line…if you build a foundation on movement (timing and awareness in motion) and the attributes necessary to deliver and apply efficient strikes, controls and finishes, you just need to add the foul or dirty tactics. It doesn't work the other way around.
Foul techniques should be used as a supplement to techniques based on leverage. Biting and eye gouging are unpredictable and not reliable as escapes from an inferior position or as a defense against a bigger, stronger opponent.
One of Gutierrez' best points is that using dirty tricks to escape a bad position escalates the fight. If they were only intending to beat you, being bitten or eye-gouged is going to make them want to hurt or maim you. This is rarely a good idea, and it is a particularly bad idea when the opponent is already in a better position!
Contrary to the arguments of light-contact martial artists, this exact scenario sometimes plays out in MMA. Gene Lebell versus Milo Savage is one example:
I land on him, then I got behind him to choke him, and he grabbed my thumb and started to bite it. I said, "Milo, you bite my finger, I'll take your eye out."
So he opened his mouth.... I reached around and I choked him out.... Poor Milo was sitting down there, and when I walked [after the victory] I 'accidentally' stepped on him.
