The Computer Between the Ears

[Russell Bowyer]

A dive computer for me is a must have bit of diving kit. Whilst I started diving before they were used, I can't imagine going diving without one. It's a bit like using a satnav (or GPS for The Americans on here) when you drive to somewhere new - I can't imagine going back to using old style maps either

 

[rjack321]

A dive computer for me is a must have bit of diving kit. Whilst I started diving before they were used, I can't imagine going diving without one. It's a bit like using a satnav (or GPS for The Americans on here) when you drive to somewhere new - I can't imagine going back to using old style maps either

We almost routinely have people following their GPS into the worst possible roads and conditions over here. Snowing heavily on a dirt road, road closed, they keep going and going until they get stuck. Happens at least once a winter here in Washington, Oregon, Idaho, northern California, and/or Nevada. Oddly enough its not common in Montana or Wyoming - fewer city folk who blindly follow the line on the tiny screen I guess.

The divers who seem to understand deco the best to me are those that don't rely on a computer very much. More than once I have talked about "what's the max time we could do at 50m?" and many heavy computer users just blank out and don't know. They can punch in the numbers and it spits out a profile they can follow, but they don't intuitively know how the basic limits of the dive interact with one another (gas & time) and which one is limiting at 20mins and which one is limiting at 40mins. Basically the computer ends up being a crutch for both their ascent profile and their gas plans.

On the other hand, back when we used the uwatec's and not much else they hid all sorts of ascent profile flaws unfortunately.

 

[Neilwood]

Strictly a recreational diver here but I follow this section a fair bit.

To my mind what the essential discussion relates entirely to is the reliance on the computer between the ears - irrespective of diving with a computer or diving using "the computer between the ears" during the dive. Why? Because in both cases we are reliant on the human brain to make the right choices. In both cases the human brain is responsible for the plan.

This might sound like semantics but consider the following:
1) The diving computer is following an algorithm by running a program written & checked by the human brain - I have never heard of any computers that can program themselves and self check.
2) The computer between the ears is attempting to run the algorithm via a predetermined plan or a deco ratio (used that term deliberately to avoid any issues with any particular system that the DIR bodies suggest) without any outside influences.

Why is that important?
In 1, the computer can be designed and thoroughly tested prior to use in "real life" with the algorithm checked and rechecked to ensure it is performing as expected. Once the testing phase is complete the diver should be able to rely on the output of the computer (so long as there is no malfunction in which case there should be a fall back plan such as a redundant computer , a SHTF deco plan or for rec diving a direct return to the surface at a safe rate). The computer however (so long as it is working correctly) is never subject to stress or circumstances that can affect its ability to function.
In 2, there can be a number of external influences that can affect how the brain is running that plan/ratio such as narcosis, timing errors, currents etc which means that should a wrong assumption be made or a calculation error be made that can be compounded. Also if some of the assumptions used in generating the plan are incorrect or not followed (ascent rate, depth etc) then the plan becomes more and more imprecise. If you are task loaded and miss a depth change or extend a time at a certain depth for whatever reason, your plan has gone. If your plan has gone astray, you might never know it until it goes badly wrong.

People will ALWAYS get bent using either system simply because neither system takes in to account exact physical factors on the day such as hydration, fitness etc. The measure with a micrometer, mark with chalk, and cut with an axe analogy comes to mind - the systems at present are only approximations of how things "should" work. The important thing we can do as human beings is minimise the chances of problems.

 

[Dan_P]

Y'know, this entire discussion reminds me strongly of how some racers talk about how unnecessary antilock brakes are for them.

Reminds me of how it might sound if drivers were seriously advocating that having a GPS makes them better drivers.
It's my experience that the exact opposite is the case.

The problem with overemphasis on computers, is a risk of lacking development in the diver's ability to think - but, more importantly - a disconnect from the diver's capacity as they progress. When you're forcing yourself to think, you will gradually familiarize yourself with the diving you're doing, and intrusively feel discomfort when you start to move towards your limit. That is, before you put yourself in the deep end of things, as illustrated so well in the examples of this string.

That's what so many divers who are forming an opinion about computer-free diving, are missing; you're not going from computer to no computer in the current dive, rather, you build up your diving and develop with it, over a long time.
But, I find it perplexing how this doesn't illuminate the obvious problem; if going from computer to no-computer in the present setting seems unnerving, surely, there must be a level of overreliance taking place.

As for accuracy, it's a joke of an argument.
One, you get pretty damn close with depth averaging.
Two, you can still confirm your avg. depth with most depth gauges, and in either case, your team.
Three, nothing in the currently available body of knowledge on the physiological decompression process prompts a requirement for minute accuracy.

I've said it before and I'll say it again - if you're diving within your limit, diving computer-free (or, shall I say, using Ratio Deco) is plenty safe and has a number of significant benefits.
I think it's in it's place to disambiguate "can't trust a computer" from "can't blindly follow a computer", and in either case, computers can't do jack diddly about factors that the human brain interprets - and they're not predictive in the way the human brain can be.

 

[rjack321]

Reminds me of how it might sound if drivers were seriously advocating that having a GPS makes them better drivers.
It's my experience that the exact opposite is the case.

The problem with overemphasis on computers, is a risk of lacking development in the diver's ability to think - but, more importantly - a disconnect from the diver's capacity as they progress. When you're forcing yourself to think, you will gradually familiarize yourself with the diving you're doing, and intrusively feel discomfort when you start to move towards your limit. That is, before you put yourself in the deep end of things, as illustrated so well in the examples of this string.

That's what so many divers who are forming an opinion about computer-free diving, are missing; you're not going from computer to no computer in the current dive, rather, you build up your diving and develop with it, over a long time.
But, I find it perplexing how this doesn't illuminate the obvious problem; if going from computer to no-computer in the present setting seems unnerving, surely, there must be a level of overreliance taking place.

As for accuracy, it's a joke of an argument.
One, you get pretty damn close with depth averaging.
Two, you can still confirm your avg. depth with most depth gauges, and in either case, your team.
Three, nothing in the currently available body of knowledge on the physiological decompression process prompts a requirement for minute accuracy.

I've said it before and I'll say it again - if you're diving within your limit, diving computer-free (or, shall I say, using Ratio Deco) is plenty safe and has a number of significant benefits.
I think it's in it's place to disambiguate "can't trust a computer" from "can't blindly follow a computer", and in either case, computers can't do jack diddly about factors that the human brain interprets - and they're not predictive in the way the human brain can be.

Hey I agree with you. Except for the part about "plenty safe"

Multiple studies have shown the ratio deco profiles can get you out of the water. But at a statistically greater risk of DCS and with more post surfacing decompression stress. "plenty" is in the eye of the beholder.

 

[Dan_P]

Hey I agree with you. Except for the part about "plenty safe"

Multiple studies have shown the ratio deco profiles can get you out of the water. But at a statistically greater risk of DCS and with more post surfacing decompression stress. "plenty" is in the eye of the beholder.

Spisni?
Reading the report, I think it'd be fair enough to state that the "panic" is blown out of proportion compared to what's actually available.
But in either case, I think deep stop emphasis is maybe best discussed as a separate topic from using "ratios" generally - I'll just say "computerless"

 

[TrimixToo]

Reminds me of how it might sound if drivers were seriously advocating that having a GPS makes them better drivers.
It's my experience that the exact opposite is the case.

The problem with overemphasis on computers, is a risk of lacking development in the diver's ability to think - but, more importantly - a disconnect from the diver's capacity as they progress. When you're forcing yourself to think, you will gradually familiarize yourself with the diving you're doing, and intrusively feel discomfort when you start to move towards your limit. That is, before you put yourself in the deep end of things, as illustrated so well in the examples of this string.

<snip>

Dan, I think you missed my point entirely, and at least to me it seems that you responded to a number of points I neither wrote nor meant. I'm not going to go through that point by point, though, nor argue with you. I have a day job, nighttime hobbies beyond ScubaBoard, and no particular wish to tilt at windmills. You have every right to choose the risks you are willing to tolerate and I'll pick the ones I'm willing to tolerate. You won't change my mind and I won't change yours, and that's fine. Others will take a look at the body of what's been posted and choose for themselves as well.

 

[rjack321]

Spisni?
Reading the report, it'd be fair enough to state that the "panic" is blown out of proportion compared to what's actually available.
But in either case, deep stop emphasis is maybe best discussed as a separate topic from using "ratios" generally.

No I don't want to discuss deep stops with you, sorry been there done that. There are 40 threads about NEDU and spisni out on the internets already. I'm not panicking

But I have pointed out for years that RD (especially as taught by UTD) is not evolving to keep pace with current science. So AG actually supports the one study examining RD in detail, which shows that his approach is more stressful than the alternative. The buhlmann approach that he's railed against for over a decade (I took GUE Tech1 from AG 14 years ago) is actually less stressful - surprise! <sarcasm font off>. Combine his long history of promoting deep stops even deeper than VPM which has been completely debunked by the NEDU work.

And what happens? You all shrug it off as no big deal, measure with a ruler cut with an axe, it all comes out in the wash, the pattern is good enough blah blah. That shows me that UTD in particular is not interested in actual decompression science and you're are more interested in holding onto your invalidated opinions than actually being "safer" or "less risky" in a statistical sense. Which totally explains why you'd continue to teach and advocate "using the computer between your ears" - its not subject to empirical testing or replication so its much harder to demonstrate how misleading and inaccurate it can be.

 

[Dan_P]

Dan, I think you missed my point entirely, and at least to me it seems that you responded to a number of points I neither wrote nor meant. I'm not going to go through that point by point, though, nor argue with you. I have a day job, nighttime hobbies beyond ScubaBoard, and no particular wish to tilt at windmills. You have every right to choose the risks you are willing to tolerate and I'll pick the ones I'm willing to tolerate. You won't change my mind and I won't change yours, and that's fine. Others will take a look at the body of what's been posted and choose for themselves as well.

Absolutely, fair game.
I'm not arguing against any point you've made, simply adding my thoughts to the conversation with a basis in an analogy you made - your diving is your business and I don't have a problem with it.

No I don't want to discuss deep stops with you, sorry been there done that. There are 40 threads about NEDU and spisni out on the internets already. I'm not panicking

But I have pointed out for years that RD (especially as taught by UTD) is not evolving to keep pace with current science. So AG actually supports the one study examining RD in detail, which shows that his approach is more stressful than the alternative. The buhlmann approach that he's railed against for over a decade (I took GUE Tech1 from AG 14 years ago) is actually less stressful - surprise! <sarcasm font off>. Combine his long history of promoting deep stops even deeper than VPM which has been completely debunked by the NEDU work.

And what happens? You all shrug it off as no big deal, measure with a ruler cut with an axe, it all comes out in the wash, the pattern is good enough blah blah. That shows me that UTD in particular is not interested in actual decompression science and you're are more interested in holding onto your invalidated opinions than actually being "safer" or "less risky" in a statistical sense. Which totally explains why you'd continue to teach and advocate "using the computer between your ears" - its not subject to empirical testing or replication so its much harder to demonstrate how misleading and inaccurate it can be.

Hold on for a moment - other than directly supporting the Spisni-trial which was a scientific study of RD, UTD did in fact reduce the deep stop emphasis as a direct result of the Spisni-study.
And that was within a year of it being published.
Granted, UTD may (or may not) have had access to the relevant information earlier, but even so, that's quick adaptation (to scientific findings) in the context of a diver training organization.

Adding that UTD doesn't force anyone to use RD but offers it as an additional option to computers with whichever algorithm you might choose, and that they state very clearly that RD is subject to personal adaptation (e.g. for reduced deep stop emphasis), I really don't think your barrage of critizism is very warranted.
And in either case, that's completely ignoring any benefit to using a "standard deco"-paradigm in general.