Unraveling the ‘Inverse Screwdriver Law’

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What does DIY frustration have to do with memory, emotion and superstition?

Has this ever happened to you: you’re working on some project where you need to tighten a screw and you reach into your toolbox, hoping you’ll get something that fits. How often does that work out the way you want? Sometimes it almost seems as though the tools are taunting you: that if you need a flat-bladed screwdriver, all you can find are Phillips head drivers, yet if you need the Phillips head driver, all you can find is flat-bladed tools. I call this phenomenon the ‘inverse screwdriver law’, a pseudo-natural law and playful poke at the way physicists write their theories.

But what’s really going on here? The answer has much more to do with the contents of our heads than the contents of our tool kits. More specifically, the inverse screwdriver phenomenon happens because of what we don’t understand about our own memories.

Human memory is intelligent in its own way. In some sense, you could say that your memory has a mind of its own. A little introspection suggests that we don’t control or have direct insight into our memory — at least, what we call our conscious mind does not. It is more the case that consciousness co-exists alongside of memory. The status and activity of memory are largely hidden from conscious awareness. Memory usually does what we want and need it to do, but when it doesn’t, we’re powerless to discipline it. We’ve all suffered from the ‘tip of tongue’ experience, when we know we know something, but simply cannot recall it at the current time.

Memory does two jobs: storage and retrieval. Storage is all but invisible, which makes life hard for students, because there’s no indicator that experience has actually been stored such that we’ll recall it later. Furthermore, we tend to massively over-estimate how much we retain.

The second task, recall, is by necessity a bit more explicit, as the results of memory must necessarily reach conscious awareness. But how that happens isn’t obvious. Memory gives us no explicit clue what specific cue or observation in the present moment triggered recall. As good students know, the only way to really prove something has been remembered is to go through the entire encoding–cue–recall cycle enough times to start to believe you’ve ‘got it.’ Worse yet, the ability to recall degrades over time, and this third process is, again, entirely outside of conscious awareness.

And memory, this semi-intelligent, semi-independent sub-part of our minds, makes its own decisions about what it will recall. All other things being equal, memory will tend to retrieve things that evoke strong feelings. And here lies the secret behind the inverse screwdriver law: getting the right screwdriver has no emotional implications at all, so memory glosses over it. But getting the wrong screwdriver is a problem. It’s annoying. It’s frustrating. And so, memory locks on to these ‘inverse screwdriver’ instances like a bulldog, and doesn’t let go. As a result, when you think about finding tools, your memory doesn’t give you a dispassionate statistical analysis of all the times you succeeded in getting the right tool versus all the times you failed, but rather, it selectively favors all the failures. From your memory’s perspective, you ‘always’ get the wrong tool, even when that’s not objectively true.

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And when you understand the inverse screwdriver law as a trick of memory, you can find its cousins everywhere. “When you forget to bring your umbrella, it rains ‘every single time’.” There’s a superstition among the technorati that computers will misbehave or breakdown more frequently when the user most needs them to work. Both of these scenarios pit two low-emotion conditions (no rain when you’ve left your umbrella at home, and a computer breaking down when you don’t really need it) against two high-emotion conditions (rain and no umbrella, and computer failure at a time of high need). Once you know how memory works, these ‘anomalies’ become tricks of our memory, rather than properties of some punitive defect in the way the world seems to handle probability.

In the world of sports, players often talk of ‘streakiness.’ Some are on a ‘winning streak’ where they can’t seem to lose, others are stuck in a ‘losing streak.’ Statisticians are not immune to the feeling that some players are ‘on fire’ while others are ‘ice cold.’ But when impartial statistical analysis is brought to bear, ‘streaks’ are nowhere to be found. Even a patently random event like a coin toss can seem ‘streaky’ to an observer. Throw a coin five times and it’s unlikely (but far from impossible) that it will come up heads each time. Keep throwing that coin, and the longer you keep doing it, the chance of seeing a ‘streak’ increases until it becomes a near certainty. We remember the streaks because they are remarkable. We are elated by winning streaks, and even more crushed by losing streaks. Grinding along with some wins and losses just doesn’t make the same impression, so by inverse screwdriver law, we’re bound to remember streaks more than we remember expected performance.

In therapy, inverse screwdriver law has important implications. Cognitive behavioral therapy (CBT) icons like Aaron T. Beck urged clients to abandon ‘always’ and ‘never’ statements (“I always mess up,” “she never listens”), not only because they’re factually false, but they cause upset with no rational basis in reality. Inverse screwdriver law allows us to go one step farther: we can agree that exaggerated statements are false and destructive, as CBT reports, but also have compassion for people who hold tight to these ideas. Beyond mere negativity is a glitch in memory that skews what we recall to the most emotionally intense and, more often than not, disturbing events. It takes effort to look past and through our memory’s recall foibles to see what’s really happening.

All clinical material on this site is peer reviewed by one or more clinical psychologists or other qualified mental health professionals. This specific article was originally published by on and was last reviewed or updated by Pat Orner Oliver on .

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