This article is fascinating. The argument is that the well-known Dunnign-Kruger effect (i.e. unskilled people overestimate their skill), is not a psychological effect. Rather, it is a statistical mistake. It is an artifact of autocorrelation: Comparing a variable to itself.
Tom Stuart is a great, clear writer. This article does a great job at introducing the usefulness of monads – explaining them from the ground up, without the math pretentiousness.
Ruby supports many ways of doing that. This excellent flow-chart from a StackOverflow answer tells you which one to use. I am reposting mainly so that I can find it again easily!