Fifteen years before he wrote it down, Roger Mullin sat his ten-year-old daughter Mhairi on his knee, asked his wife Barbara for paper and a pencil, and started to draw.
Mhairi’s parish priest, Father Pat, had died suddenly.
She had never been to a funeral. She did not know what a coffin looked like, whether she would be able to look at it, whether she would cry too much in front of everyone and have to leave before she got to say goodbye. Her mother had spent an evening trying to talk it through with her, gently and patiently, and it had not worked.
Mhairi was, in Roger’s words, “all mixed up inside.”
Roger Mullin has taught decision making for over twenty years. At the time, he taught Decision Support Systems at the University of Stirling. Barbara was midway through an Open University course on the same subject. When Roger suggested drawing a decision tree with a grieving ten-year-old, Barbara has since admitted she thought her husband had lost the plot. She sat down anyway, mostly to see how badly it would go.
It didn’t go badly. Roger drew a box: “Mhairi’s difficult decision.” Two branches grew out of it: go to the funeral, stay at home. Down each branch, he asked her what might actually happen. Down each outcome, he asked her how likely it felt, and how much it would matter to her if it happened. She put numbers on things she had never been taught to measure. A ninety-five per cent chance she’d be badly upset if she stayed home. A value of one hundred on getting to say goodbye properly, zero on making a fool of herself and having to leave.
By the time the arithmetic was done, the tree said go. Mhairi went. She got through the service. She was glad, afterwards, that she’d gone.
Roger, Barbara and Mhairi wrote the whole exchange up as a case study, published in the journal Judgment and Decision Making in December 2008, with commentary from two working decision analysts, Jack Dowie and Rex Brown. Roger is a friend, and he sent me the paper this week. I have been turning it over in my head since.
The thing that stops most people using a tool like this is the assumption that structure and feeling are opposites. That bringing a framework into a hard moment is, by definition, a cold thing to do. Barbara believed that too, walking in. What she watched instead was her daughter’s crying slow down and then stop, not because anyone told her to feel better, but because she could finally see the shape of what was tangled up inside her. The tree didn’t remove the grief. It gave the grief somewhere to sit so that Mhairi could think past it.
I see the same tangle in founders and business leaders across the Highlands more often than I’d like. Not tangled about grief, obviously, but about a decision they cannot get their head fully around because there is too much riding on it and too much noise around it. Whether to apply for a loan that comes with conditions that will shape the business for years. Whether to keep a client who pays well but is quietly wrecking the team. Whether to close a location that has never quite worked, or give it one more season. I have sat across the table from people at exactly this point, not short of information, short of a way to see it clearly.
What Roger did with Mhairi is not complicated, and you do not need a background in decision theory to do a version of it yourself. Name the decision honestly, in one sentence. List the choices you are actually weighing, not the ones you think you should be weighing. For each choice, write down what could genuinely happen, the good version and the bad version. Put a rough sense of how likely each outcome feels, out of ten if percentages feel like homework. Put a rough sense of how much each outcome would matter to you if it happened. Then look at what the numbers, rough as they are, are quietly telling you.
It will rarely tell you something you didn’t already suspect. That is not a failure of the method. The value is in seeing your own instinct laid out plainly enough to trust it, or plainly enough to notice it’s wrong.
There is one caveat worth keeping, and it comes from the paper’s own commentators. Jack Dowie and Rex Brown, responding to Roger’s case study, both pointed out that Mhairi’s tree used a single measure of value and no outside check against how other people in similar situations had actually felt afterwards. A ten-year-old working through grief with her father is one thing. A business decision with money and people attached to it deserves the same tree, and then, perhaps, a phone call or two to someone who has actually lived through the equivalent. The tree shows you the shape of the decision. It does not replace the judgement of people who have been where you are about to go.
Mhairi is a grown woman now, a speech and language therapist, still willing to be named as a co-author on the paper that came out of the worst week of her ten-year-old life. That says something about how it felt to be helped that way, rather than simply comforted. Structure, done properly, is not the opposite of care. Sometimes it is the clearest form it can take.
You can read the full academic paper here: https://sjdm.org/~baron/journal/81128/jdm81128.pdf
This case study, Mhairi’s Dilemma: A Study of Decision Analysis at Work, was published in the Journal of Judgment and Decision Making (2008), and has also been published by Cambridge University Press (2023).
