(This originally appeared at Globis.jp, in a series on critical thinking.) Assume makes an ass out of you and me. A high school baseball coach was the first person I ever heard say this. A teammate had thrown behind the runner – sending the ball to second base as the runner ran to third – an error that even a Little Leaguer would recognize. The coach, red-faced and clenched teeth, but valiantly striving for patience, approached the player between innings: “The runner’s going to third, not second. Why in the world are you throwing the ball to second?” “Coach, I assumed he would want to stop at second.” The coach blinked for an instant – stunned, as if he’d been hit in the head. Then he let out a bellowing laugh and walked away shaking his head. He stopped at the far end of the bench. “You assumed he would want to stop at second? He’s playing baseball. He wants to run home just like everybody else. Son, let me tell you something: Assume makes an ass out of you and me, and don’t you forget it.” Erroneous assumptions when exposed are often laughably foolish. Until then, they masquerade behind unquestioned respectability. Allow me to explain. On a spring Sunday morning I ask my son, Andy, what he wants to do. We have time and weather with us. We are up early and the day full of possibilities. He mimes riding a bicycle, “Bike riding.” He’s an accomplished cyclist and so I offer as a destination Innokashira-koen, the big park near Kichijoji station. We’ve done the ride only once before so I know it will still be interesting to him. I’m concerned that it’s a long ride, following the Kandagawa canal, and he seems tired from the overnight visit to his aunt’s house, where he played a lot and slept little. But, I decide that we can take our time, stopping to play at the smaller parks along the way. If he proves too tired, we can turn back short of the destination and it will still be a pleasant ride. Soon, we are on our way, pedaling under the trees along the canal. One of the first things we learn in critical thinking is how uncritical we are of our own assumptions. Perhaps, the most serious problem is that we have difficulty seeing that others don’t share our assumptions. We tend to think our audience understands us and that they can easily see our point of view point because it makes so much sense to us. When we receive an affirmitive answer to our position, we rarely check to confirm that the audience a) understands our idea, b) shares our assumptions about it, and c) is actually agreeing to what we proposed and not something else. The first park we come to is in an older neighborhood and it seems that most of the children have grown up and moved away. Some areas in the park are even overgrown with grass. We play on a ship styled from concrete, but soon return to our bicycles. We ride on to a second park, a wide expanse sheltered by a giant ginko. The main attraction is a long slide with rollers, like a factory conveyer. We play a long time there. When we leave the sun is overhead and we can feel it. As we continue along the canal, Andy begins to have trouble keeping my pace. Usually, it is the opposite. I ask several times if he feels good enough to continue and he insists that he does. We go on. Assumptions help us to narrow our data into useful form. They make the cup we fill from the data firehouse, which, if left unconstrained, would overwhelm us. But assumptions can also be misleading, allowing us overlook important information. Too often we fail to ask why enough times because we like being quick with a decision as much as we like being right. Combine that with our inclination to assume that our audience shares our assumptions, and we have a potentially calamitous situation. We have no clue – or rather fail to note the clues — until it all is undone. We stop at a third park — cool and dark, with a carp pond and a meandering stream. I watch Andy push his bicycle along the edge of the pond. The usual excitement in him just isn’t there. I buy a sports drink from a vending machine and he drinks some and brightens for a fleeting moment. Again, I ask if he’d like to turn back, and again he declines. We continue toward Innokashira, but the spirit of a forced march has descended on our excursion. Soon, he lags far behind and then stops. I come back to him and offer the sports drink. He waves it away, “How much farther?” We are still far from Mitakadai station. Beyond there the path widens into the park. We need to go back, or it will be a problem for him to return home. He begins to cry. I’m stunned. Why is it such a tragedy to turn back? It’s been a good ride. It’s been fun. Why in the world is he crying? “I wanted to see the animals,” he says. Animals — what animals? At that moment I’m as lost as my baseball coach had been. Animals? When we are confronted by our erroneous assumptions, it often takes time to let them go. We don’t want to be wrong, let alone foolish. Sometimes, though, it takes just a few seconds because we may have suspected that we were wrong all along and it has become painfully clear. Finally, I got it: Two weeks before on a school field trip, Andy had visited the zoo on the far side of Innokashira park. He had understood my offer to ride to the park as a ride to visit the zoo. He knew that he was tired when we started, but wanted to visit the zoo again. He wanted to show me the animals and tell me all the interesting things he had learned. Meanwhile, I had assumed that riding to Innokashira meant going there and turning around. Wasn’t it obvious? Of course, it was not. I offer to take him the next weekend to visit the zoo – by train. He agrees. After a break at a convenience store, he gamely rides home. How blithely we expect that we are understood and our assumptions are shared; that people know what we’re talking about especially when they agree with us. This is even truer for managers and team members under time pressure to execute. Sometimes, assume makes an ass out of you and me. Especially, me.