Pedagogical Pattern #18
The Three Bears Pattern
(Version 1.0)
Kent Beck
70761.1216@compuserve.com
 
INTENT 
Remove "fear of failure" as a barrier to learning by making failure part
of the goal.
 
MOTIVATION
Learning is experiential. Without experience, there is no learning. However much
the learner wants to learn, getting over the barriers to experience can impede
or even completely block learning.
Confident learners to use failure and frustration as investments whose payoff
comes in future success. Most traditional schooling systems are so effective at
punishing failure that the confidence to fail is rare and dearly bought (and who
said the school system can't teach?)
 
Many topics challenge the learner to find a balance along some continuum. How
much should a point guard shoot? How often should a developer refactor? How
strictly should a musician follow the rhythm? Effectively answering these
questions requires that the learner discover a position or range along a
continuum from "too much" to "not enough".
 
Learning to find a balance poses particularly severe barriers to gaining
experience for the learner. There is no chance the learner will be successful
the first time, unlike many other learning activities. Even if they fell into
the right balance, chances are the learner would not recognize that the balance
would be struck.
 
STRUCTURE
Continuum- Define the continuum for the learner. A simple approach is to explain
 the reductio ad absurdum on either end.
 
Experiment- Give the learner a chance to locate the balance in three places-
either end of the continuum and right in the middle.
 
Review- Give the learner the chance to reflect on the three experiments.
 
Implementation:
1. Define the continuum- I have had good luck with the reductio ad absurdum
strategy. I also like posing a set of questions that will be asked of the
resulting balance. For example, in reviewing the point guard's decision about
how much to shoot, I would ask "Did the other players get into the flow of the
game?" "Was the defense forced to guard you closely?" "Did you win?"
 
2. Conduct the experiment- You want the learner to experience all three options
close enough in time to accurately compare them. Reduce the topic to something
that can be accomplished in less than an hour, if possible.
 
3. Review the experiment- One technique I've found helpful is to have the
 learner briefly present the three solutions, then have the rest of the class
guess which was which. This can help learners who haven't yet learned the true
boundaries of the continuum.
 
CONSEQUENCES
+The learner has failure as a goal, so fear of failure will be less of a
problem. Some learners just can't get over the fact that they "have to do it
right" eventually, however.
+The learner understands the continuum by explicitly experiencing its ends.
-You may have over-simplified the topic for the learner by reducing the topic to
a single continuum.
 
KNOW USES
I may have picked this technique up from "Disney Animation: The Illusion of
Life" by Frank Thomas and Ollie Johnston. In it, they relate the story of a
frustrated Walt Disney telling his animators to exaggerate the movement of
characters. The result was just what he was looking for.
 
I have taught requirements engineering with this technique. I ask the learners
 to write stories that will define the system- one too large in scope to be
useful, one too small, and one just right. I taught this technique in India and
ended up telling the story of Goldilocks and the Three Bears after lunch.
 
I have taught pattern writing with the Three Bears. Tyro pattern writers often
struggle to find the appropriate scope for their patterns.
 
I use The Three Bears in my own learning all the time. When I got a Smalltalk
with the constraint-ish ValueModel framework, I deliberately wrote a system that
used it too much. When I learn a piece of music, I deliberately play it like a
metronome and with the beat wandering all over.