**mechanisms**to speed up things. For instance, if we come up to a situation that we have experienced before, we simply

**shortcut**things and

**repeat**the same

**decision**we did the first time. Which in fact makes sense: if we already thought about it and there's nothing new to add, why should we waste our time thinking about it

**again**, right?

In fact, if you think about your own morning routine when you get up you'll probably get to the conclusion that if you had to think about everything you do in order to make the best decision possible it would take you more than 24 hours to get up, get dressed and have breakfast...

## What is self-herding?

In**behavioral economics**, self-herding (which oddly enough I couldn't find any reference in Wikipedia) is a

**cognitive bias**of ours that refers to our tendency to

**repeat decisions**that we have made in the past. And this relates exactly what I just said. Now, by itself this is a good thing that we do: we recognize a

**pattern**, we check that "we've been there" so we

**jump**to the conclusion instead of going to the process of

**deciding**again what is the

**best option**for that case. But what happens when

**something changes**, even if slightly? How do we behave when our initial

**decision**was a

**bad**one?

This is what this 2 part article is about: this first part (this one) is about the

**subjectivity in numbers**(with a somehow dense example if you're not into physics and math) and the second part (due to be published next Friday) is about

**perpetuating mistakes**just because we made a

**wrong decision**the first time.

## So how do you feel about numbers?

Weather you feel comfortable with numbers or not, there is a general notion that

**numbers are objective**: if something happened 15 hours ago, it didn't happen 20 hours ago, right? We**feel safe**about numbers, numbers can't get us wrong. Or can they?## What about a black hole lighter than air?

Actually this should be rephrased to “What about a black hole with a smaller average density lower than air”.Sometimes you get really odd results that question your perception of things and force you to take a second look at what’s going on. When those results appear in the form of numbers, this strange feeling is sharper because we feel that

**numbers are objective**. This usually happens because (i) you're trying to apply rules that don't fit in your particular case or (ii) you just proved your perception wrong. And to show you this I’ll walk you through black holes and prove your perception wrong. I choose this example because I believe it is both appealing and accessible, although you have to do a little math and understand some physics concepts. I'll present it first just by arguing and then show you how to perform the calculations to reach these conclusions.

## It matters to Project Managers

This is relevant to Project Management because Project Managers try to be as**objective**as possible. On doing this we use

**numbers**on every possible occasion in the hope that this removes all

**subjectivity**. But guess what: that is not always the case. Even numbers can mean

**different**things to

**different**people. So my message is: be careful with the numbers you present; double check to see if everyone understands them the same way you do.

OK, are you ready?

## Now for the black holes

You probably have the notion that a black hole is an extremely dense astronomical object and we can start with that. Extremely dense is an euphemism: if we could turn our planet Earth into a black hole, it would fit into something like a box of matches, that’s how extremely dense black holes are.Just let me introduce a couple of concepts starting with the event horizon. The event horizon is the boundary where light cannot escape because the required escape velocity (the other concept being introduced) would be greater than the speed of light – and there’s nothing with the ability to travel faster than light. The escape velocity is how fast you have to get to bypass a gravitational pull, like the necessary speed you have to get to put a satellite on orbit. The gravity is so big for black holes that even light cannot escape - thus the name black hole. And this creates a boundary that separates both worlds. Although mass can go into a black hole from the outside in, nothing ever can move from the black hole to the outside – not even light.

Probably there's nothing here to challenge your knowledge, right?

## But now we get to the funny part

Now suppose we have a black hole with the mass of the Sun to start with. Now suppose we add some mass to it. Suppose you get the mass of the black hole to be twice its original mass. What happens to the event horizon? It grows twice too: twice the mass, twice the distance. The funny part is that the density drops tremendously because the volume of the sphere grows much, much more than twice.If you keep on adding mass to a black hole you will eventually get something as big as our Solar System. And if you have such an object, the average density is… lower than air’s density.

Hum? Can a black hole be less dense than air? Yes, it can! In fact, this is what happens to at least some massive black holes, like the

This is very counter-intuitive. But true. Do you want to check out the math behind this?

## The math behind

Let’s start with the mass of the black hole and then compute the radius of the event horizon.You can calculate the escape velocity using

where v

_{e}is the escape velocity (the speed of light in our case), G is the gravitational constant, M the mass and r the radius (what we want to find out). If we isolate r, we get

_{e}, G and M) and use a spread sheet to compute this. And we get:

No. of Sun masses | Radius (meters) |
---|---|

1 | 2,954 |

2 | 5,908 |

2,000 | 5,908,235 |

200,000 | 590,823,541 |

2,000,000 | 5,908,235,406 |

20,000,000 | 59,082,354,056 |

200,000,000 | 590,823,540,562 |

2,000,000,000 | 5,908,235,405,623 |

To calculate the density we must divide the mass by the volume of the sphere which is calculated using the formula

And now we get:

No. of Sun masses | Radius (meters) | Density |
---|---|---|

1 | 2,954 | 2,046,541,923,579,763,710 |

2 | 5,908 | 511,635,480,894,940,930 |

2,000 | 5,908,235 | 511,635,480,895 |

200,000 | 590,823,541 | 51,163,548 |

2,000,000 | 5,908,235,406 | 511,635 |

20,000,000 | 59,082,354,056 | 5,116 |

200,000,000 | 590,823,540,562 | 51 |

2,000,000,000 | 5,908,235,405,623 | 1 |

Air has a density a bit higher than 1 and you can get a black hole with an average density of 1. See? I wasn’t pulling your leg… Just a final note: having an average density of 1 doesn’t mean that matter is evenly distributed on a black hole or that these huge black holes are made of air.

## Again, this matters for Project Managers

This matters for Project Managers because numbers can have different**meanings**to each person. It’s not the example itself that matters, but what can happen when you happily report a CPI of 110% and an SPI of 115%. If your audience doesn't know about

**Earned Value Management**you could as well report it in a language only known to you. And this is for starters alone.

And finally, relating this back to self-herding, what exactly happened here? Why was there such a

**mismatch**between reality (black holes can be as dense as air) and our

**perception**(black holes are very, very, very dense)? The thing is that we've heard that black holes are very dense. I've known for a fact that a black hole with the same mass as our planet (which apparently cannot exist) would be the same size as a box of matches. But then we changed things: we made the black hole really bigger, like 2 billion times the mass of the Sun instead of the mass of Earth. But somehow, we expect the same logic (extreme density) but that logic just doesn't work anymore.

Now think about this for a minute: when was the last time that you were so sure about something even though things changed a bit, that you didn't take the bother to think it over again? Isn't this why so many internationalization initiatives fail, because people expect to do business the same way everywhere they go? This is just an example, but do think about it for a minute, will you?

The first part of this article was about

**self-herding**when the context changes a bit (larger objects or a different culture, for example). The next and final part will still be about

**self-herding**but this time it will be about the difficulty of correcting a wrong decision - when that decision was some time ago. I hope you have enjoyed this!

Continue to part 2

Posted by Luis Seabra Coelho

## No comments:

Post a Comment