Saturday, 25 March 2017

Critical thinking

There are a lot of memes around - ideas and rituals that get passed on to people and spread by word of mouth (or worse, the Internet), even distorting and evolving and they spread.

Some of these are plain silly.

My kids all seem to have got the idea that you should never, ever, set the volume control on your car stereo or TV to an odd number. Why? because it is bad luck! Personally I think it is bad luck to be superstitious.

Some may have had a good reason once.

Our industry is not immune to this - BT would always set Ethernet ports on leased lines to no auto negotiation, fixed full duplex and fixed speed. Why? nobody really knows. Many "CISCO people" say the same. The best explanation I ever got is that when auto negotiation first came in it had a lot of problems and this was the work around. These days that is simply not the case, but the work around persists causing its own problems. A better work around of fixed settings announced by auto-negotiation never seems to get used. Historical problems have led to a meme, one we are stuck with mostly and will be for years to come. To be honest, we have much the same feeling in the office when it comes to spanning tree having been badly bitten by that years ago and with no real reason to think it is actually a problem now, but we don't really want to risk it.

Some may be a basic misunderstanding.

Setting a thermostat to max to get to desired temperature more quickly. This drives me nuts and I posted on how it was even applied to an oven. In the car, if it is cold the temperature gets set to max (like 30 ℃), then it ends up too hot, so it is set to min (16 ℃) and this is repeated! Setting to 21 ℃ does that for you, and gets to 21 ℃ just as fast as if you set to 30 ℃. Somehow people don't understand how things actually work, not realising the binary nature of the output of most thermostat based systems. This "solution" works for them, well, sort of, so they don't question it. Indeed, people refuse to understand why they may be wrong! We had much the same when air-con installers said never use "auto" mode, but could not in any way explain why that was a problem, or, if it was a problem, why manufacturers include the feature. At work the auto mode allows the two control temperatures to be set and to allow a narrow range. At home there is one setting an around ±2 ℃ making an annoying 4 ℃ window. Apart from an "economy" mode making the window wider I have no other control - so I end up using "heat" in winter and "cool" in summer so as to maintain a more controlled temperature. But this was not an explanation the installers had, and would not apply to the more controllable office system they were installing.

Some come with their own explanation.

The first thing I do is ask "why?". This is the critical thinking, and I think I have managed to get my kids to do the same. The odd numbers on volume does rather surprise me, but I think that falls in to "playing a game" rather than a lack of critical thinking. If there is no explanation then I don't do it or pass it on. If we were all like that then stupid memes would die out. However, some memes come packaged with their own plausible explanation. This is clever as it is basically targeting the critical thinkers. Ideally it is an explanation that is plausible but hard to verify. Sadly the explanation may be totally made up, as part of the way memes are spread - someone once asked why and someone made a guess or invented an answer and it stuck. There are examples like "why never boil the kettle twice" which often comes with "because every time you boil it you reduce oxygen, and so boiled twice does not taste as good". See this (with some nice graphs) for a clue why that is almost certainly bullshit. One clue is when the same meme comes with a variety of unrelated "explanations".

Sometimes the explanation is the meme.

Sometimes the whole meme boils down to the made up explanation - and this spreads because people want to be smart and tell someone something they know and the other person did not. Of course, when the explanation is made up, there can be a counter meme to explain why actually that is a common mistake. I suspect there are cases where these exchanges can go on several times.

Even so, memes, these stories and "facts" and rituals that float around, are an interesting topic. I am sure that once upon a time, before books and the Internet, they were essential in ensuring collective knowledge allowed people to learn from other's mistakes.


  1. I've always liked to think of these as memetic viruses, rather than memes: self replicating corrupt ideas.

  2. Maybe this:

  3. The BT thing changed long ago when the ADVA FSP 150 product started to be used to terminate leased line services.

    On fibre-delivered services they now expect you to have AutoNeg ON - but the capability advertisements will only offer Full Duplex.

    See SIN476 (for 21CN Ethernet) and SIN492 (for EAD).

    Oh and don't get me started on people turning off AutoNeg on 1G links.......

  4. WRT car heating/cooling. Whilst I don't disagree with your interpretation of what the thermostat does in a modern climate controlled car, there is another element; The temperature of the person (and the car interior).

    If you go out on a hot summer's day (perhaps for a long walk) and then if you enter a A/C space (such as a car or shop etc) where the air temperature is 21℃ you will notice that the air is cooler, but you will not _be_ cool straight away. You have a heat capacity, you take time to cool down. In such a situation you would likely be more comfortable if the air temperature in your new environment was lower than 21℃, perhaps 16℃, until you have cooled down. Indeed having the air temperature in this new environment be 16℃ will aid your cool down.

    Hence setting your car temp to 16℃ when you get into it on a hot day is not unreasonable, as long as you increase it back to 21℃ (ish) when you and the interior of the car (ie the seats) have cooled down.

    1. An interesting view, but that is not really what people are trying. That would be someone [over] thinking it, and maybe has some merit. It seems to be just an unwillingness to understand actually how it works. See

  5. Your kids are wrong - you should always set the volume to an odd number - 11.