How Much of Sonography is an Illusion? Better Ask the The Brain: It Could Use Some Better Support (and get out a little more often)… A Height Estimation Illusion

In carpentry (and all construction), the rule is to measure twice, cut once.  And though a seasoned woodworker can estimate by sight down to very small dimensions, she or he never would.

We work with materials more priceless and spatial judgements more critical, but how often do we find ourselves acting on an estimate: fetal femur length, renal size, ventricular ejection fraction… so many other things throughout our days.

We’ve all met the clinician who can analyze all the data as fast as he can dictate, the genius who can eyeball the image and categorize every dimension as fast as a court reporter types.  And why not?   Ten thousand hours of practice and you’re an accomplished expert.  You’re qualified like no one else.

So, today’s little exercise will amuse, or perhaps trouble you.  You’ll decide.

And either way, you’ll see once more why to never trust your eyes alone….


What do you see? Where’s the Red Dot?

Screen Shot 2023-11-10 at 5.21.15 PM

It’s located halfway up the triangle, although it appears to be much higher.  If you’re like most of the rest of us you’re going to want to measure it out to put the illusion to rest, because your brain isn’t going to give up on this one easily.

This is a variation of the Inverted T illusion (more on that later on this year), of which vertical lines are judged to be of greater extent than horizontal lines of the same length.


The lesson for Sonographers (and all Imaging Professionals):

It’s pretty obvious: take the time to measure before you think, before you speak, before you act.  Not one of us is above the delusion of the mind.

Even though you now know the red dot is equidistant from the base and the apex, it still looks off center.

In the CT report, six-year-old’s brain tumor looked on the midline (and thus likely malignant).  On the CT image, the tumor measured off the midline (and probably benign).  And in the OR, the frozen section (and final path analysis) showed it to be the most malignant form of brain cancer possible.

Now, look one more time at the red dot: What do you see?

It doesn’t matter: Measure.


And the lesson for the Rest of Us:

Psychiatry and Psychology Professionals have disagreed among themselves for generations over many things, but on this one point there is near unanimous agreement.  It has to do with one of the most malignant brain diseases in existence, one that affects nearly every one of us: our tendency to overestimate the gifts of others and underestimate our own.

Consider the practical IQ (or effective genius) of the person already in your field that you’re most in awe of. You know, the one who can eyeball a complex set of data and crank out an authoritative analysis of it as fast as a super computer; the one that can lay out a project like Edison and complete it like Super Girl; the one who can capture any audience’s attention–and hold it–on any topic.  Chances are, the experts say, you’re making your estimate far too high.

Now do the same for you.  Unless you’re the rare, self-absorbed narcissist, you tend to estimate your own potential and talent a little too low. Those same Brain Experts tell us that your reality lies somewhat higher than you give yourself credit for.

Whether you’re off by too much or too little, whether your aim is too high or your view too low, your mind (like everyone else’s) is misled by the irrelevant elements lying outside the facts.

You’re being misled by the outliers, whatever form they take. Ignore them, cover them up, tolerate them, or maybe even enjoy them… but take time to pause for a moment and take critical, dispassionate, heartless, and sterile measure.

Do it twice….


By the way: the Red Dot is still sitting at the exact midpoint between the base and the apex….

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