The Dunning-Kruger Effect – I don’t know

Interviewing people is always a rich source of anecdotes, or should that be anec-dont’s? Whatever.

When interviewing for a technical specialist, such as a senior Oracle DBA, it seems important to ask a number of technical questions to ascertain the competency the individual has in relation to Oracle and the technologies related to Oracle. This is where the Dunning-Kruger effect comes into play beautifully.

Kruger and Dunning proposed that, for a given skill, incompetent people will:

1. tend to overestimate their own level of skill;
2. fail to recognize genuine skill in others;
3. fail to recognize the extremity of their inadequacy;
4. recognize and acknowledge their own previous lack of skill, if they are exposed to training for that skill;

So, lets ask a technical question of the candidate:

Under what circumstances will the optimizer decide not to use an index?

Here’s 4 extremely confident actual answers from 4 different candidates. This was the extent of their answers, although some (but not all) did elaborate further:

• when you do a count(*)
• when the columns you are selecting are not indexed
• I query using a table and build a SQL Profile to bypass the index
• it depends on the join condition

All candidates were OCP certified with at least 10 years worth of Oracle experience on their CV’s, applying for a senior position. To quote Darwin: “Ignorance more commonly begets confidence than does knowledge”. I like to think that it’s our brains protecting us from ourselves.

I mean… how hard is it to say “I don’t know” ? For some nationalities, that would appear to be impossible. A long time ago I spent several weeks teaching programmers in a country whose native/official language was not English. Given I am from the North of England, there are some who would say that this is also the case for me, given my notable regional accent. The combination of my idiosyncratic dialect, combined with the unnamed-county’s locals’ inability to lose face by saying “What you talkin’ about Neil?”, like Gary Coleman might have, meant that the second week of training was spent going through exactly the same materials as the first week, as it took me that long to realise they didn’t have a clue what I was saying half of the time. If only one of them had been brave enough to say (or I had been a little smarter and realised) then it would have save a whole lot of pain. However, the locals might never come understand what happens when you get “your knickers in a twist.”

NOTE: I do appreciate that I could be a Dunning-Kruger “victim” and these blogs merely indicative of immense incompetence. I’ll let you decide. 😐