Ignoring the unimportant

Before I get into the subject of today's post, I want all of you to watch this two-minute video, entitled "Whodunnit?"

*****

How many of you were successful?  I know I wasn't.  I've watched it since about a dozen times, usually in the context of my neuroscience class when we were studying perception, and even knowing what was going on I still didn't see it.  (Yes, I'm being deliberately oblique because there are probably some of you who haven't watched the video.  *stern glare*)

This comes up because of some recent research that appeared in Nature Communications about why it is we get tricked so easily, or (which amounts to the same thing) miss something happening right in front of our eyes.  In "Spatial Suppression Promotes Rapid Figure-Ground Segmentation of Moving Objects," a team made up of Duje Tadin, Woon Ju Park, Kevin C. Dieter, and Michael D. Melnick (of the University of Rochester) and Joseph S. Lappin and Randolph Blake (of Vanderbilt University) describe a fascinating experiment they conducted that shows how when we look at something, our brains are actively suppressing parts of it we've (subconsciously) decided are unimportant.

The authors write:

Segregation of objects from their backgrounds is one of vision’s most important tasks.  This essential step in visual processing, termed figure-ground segmentation, has fascinated neuroscientists and psychologists since the early days of Gestalt psychology.  Visual motion is an especially rich source of information for rapid, effective object segregation.  A stealthy animal cloaked by camouflage immediately loses its invisibility once it begins moving, just as does a friend you’re trying to spot, waving her arms amongst a bustling crowd at the arrival terminal of an airport.  While seemingly effortless, visual segregation of moving objects invokes a challenging problem that is ubiquitous across sensory and cognitive domains: balancing competing demands between processes that discriminate and those that integrate and generalize.  Figure-ground segmentation of moving objects, by definition, requires highlighting of local variations in velocity signals.  This, however, is in conflict with integrative processes necessitated by local motion signals that are often noisy and/or ambiguous.  Achieving an appropriate and adaptive balance between these two competing demands is a key requirement for efficient segregation of moving objects.

The most fascinating part of the research was that they found you can get better at doing this -- but only at the expense of getting worse at perceiving other things.  They tested people's ability to detect a small moving object against a moving background, and found most people were lousy at it.  After five weeks of training, though, they got better...

... but not because they'd gotten better at seeing the small moving object.  Tested by itself, that didn't change.  What changed was they got worse at seeing when the background was moving.  Their brains had decided the background's movement was unimportant, so they simply ignored it.

"In some sense, their brain discarded information it was able to process only five weeks ago," lead author Duje Tadin said in an interview in Quanta.  "Before attention gets to do its job, there’s already a lot of pruning of information.  For motion perception, that pruning has to happen automatically because it needs to be done very quickly."

The last thing a wildebeest ever ignores.  [Image licensed under the Creative Commons Nevit Dilmen, Lion Panthera leo in Tanzania 0670 Nevit, CC BY-SA 3.0]

All of this reinforces once again how generally inaccurate our sensory-integrative systems are.  Oh, they work well enough; they had to in order to be selected for evolutionarily.  But a gain of efficiency, and its subsequent gain in selective fitness, means ignoring as much (or more) than you're actually observing.  Which is why we so often find ourselves in situations where we and our friends relate a completely different version of events we both participated in -- and why, in fact, there are probably times we're both right, at least partly.  We're just remembering different pieces of what we saw and heard -- and misremembering other pieces different ways.

So "I know it happened that way, I saw it" is a big overstatement.  Think about that next time you hear about a court case where a defendant's fate depends on eyewitness testimony.  It may be the highest standard in a court of law -- but from a biological perspective, it's on pretty thin ice.

********************************

This week's Skeptophilia book recommendation is by the team of Mark Carwardine and the brilliant author of The Hitchhiker's Guide to the Galaxy, the late Douglas Adams.  Called Last Chance to See, it's about a round-the-world trip the two took to see the last populations of some of the world's most severely endangered animals, including the Rodrigues Fruit Bat, the Mountain Gorilla, the Aye-Aye, and the Komodo Dragon.  It's fascinating, entertaining, and sad, as Adams and Carwardine take an unflinching look at the devastation being wrought on the world's ecosystems by humans.

But it should be required reading for anyone interested in ecology, the environment, and the animal kingdom. Lucid, often funny, always eye-opening, Last Chance to See will give you a lens into the plight of some of the world's rarest species -- before they're gone forever.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

Invisible lung gorillas

In recent posts, I've made the point more than once that eyewitness testimony is inherently flawed because of built-in inaccuracies in our perceptual apparatus.  Put simply, we are just poor observers.  Not only do our brains sometimes make stuff up, we also remember events inaccurately, and given appropriate priming, interpret things based on what we thought was happening. 

None of this is meant to malign our brains, honestly.  They are extraordinarily good at a great many things, and evolution has crafted them into a data-processing device that is orders of magnitude more complex than the best computer in the world.  The fact that they fail sometimes is only to be expected.

You can't be good at everything, after all.

However, a recent experiment, done by Trafton Drew, Melissa Vo, and Jeremy Wolfe of Brigham and Women's Hospital of Boston, has delivered yet another blow to our opinion of the brain's accuracy.  And this one is not just humbling, it's downright scary -- especially to anyone who has had to rely on the skills of medical professionals.  [Source]

The trio recruited a group of 24 trained radiologists as volunteers, and an equal number of average, non-medical types.  The volunteers were given a set of lung CT scans from five different patients to look at on a computer, and were instructed to click on any anomalous nodules they saw.  (The untrained group were given a brief description of what they were looking for.)  The nodules were small, and there were only ten of them in the hundreds of scans analyzed.

What they didn't tell any of the volunteers, however, was that hidden in the slides of the final patient was an image of a gorilla.  (The gorilla was chosen because of the seminal study of inattention, by Simons and Chabris -- see their famous video here.)  The gorilla image was huge by comparison with the nodules -- an estimated 48 times larger than the typical nodule size.

Twenty of the 24 radiologists, and all of the untrained volunteers, didn't see the gorilla.

And it wasn't hard to see.  Every single one of the people who didn't see the gorilla were shown the slide in question afterwards, and asked, "What is that?" and they all answered, "That's a gorilla."  Nevertheless, the vast majority of people who had analyzed the image closely didn't see what was right in front of their faces.  (The phenomenon has been named "inattentional blindness.")

Now, to their credit, the radiologists, who presumably would know that a gorilla in your lungs is abnormal, were better at spotting the anomaly than the average guy.  They were also (reassuringly) way better at finding the nodules.  But this once again punches a hole in our certainty that what we notice (and remember) is what is actually there.

I'm often asked -- usually apropos of UFO sightings, and less commonly about phenomena such as hauntings -- why I am so skeptical, when eyewitnesses report thousands of encounters every year.  It's not, honestly, that I think it's impossible that there is something weird out there; especially in the case of UFOs, I think that the likelihood of life elsewhere in the universe is near 100%, and I'd be mighty surprised if some of it didn't turn out to be intelligent.  (Why they'd want to come here, though, is a bit of a mystery.)  So, my beef isn't that I think the claim is impossible.  My problem is that eyewitness testimony is so inherently flawed that I need more than just your claim of having seen a UFO in order to believe it myself.  (In fact, I need more than just "I saw it," as well.  I don't trust my own brain any more than I trust yours.)  Our perceptual systems are simply too easy to fool, and too poor at remembering details, to be reliable recorders of data.

So, anyway, that's the latest from neuroscience.  More evidence of the inaccuracy of the human brain.  Makes me wonder what I'm missing, as I wander through my day -- all the stuff I'm not noticing.  Probably most of it is trivial, and it's just as well that my brain dismisses it -- but you have to wonder how many times something truly marvelous crosses your path -- the equivalent of an invisible lung gorilla -- and you don't see it.

Priming the paranormal

There's a familiar cliché, that "you see what you are looking for."  It's something that I think we can all relate to; our perception is often limited by what we already thought was there.  That our perceptual/integrative systems are inaccurate we've known for years; experiments have supported the conjecture that when our attention is focused, we can miss major features of what we're seeing.  (If you don't believe it, check out this amazing video -- it's less than two minutes long and will blow your mind.)  Further, when we already have preconceived notions about what we are going to see, we tend to find it whether it actually exists or not (this is the basis of the logical fallacy confirmation bias).

This latter point was the subject of a brilliant little study by Chris Jensen Romer, funded by the Society for Psychical Research, and which was just published this week.  It bounces off (and improves upon) a 1996 study by Houran and Lange, which looked at how individuals who are primed to notice "paranormal occurrences" in their houses mostly... do.

Romer's study, which is outlined in more detail here, involved five couples keeping a diary of "unusual or unexplainable experiences" that occurred in their homes over a one-month period (between October 17 and November 17, 2012).  Here were the instructions that were given to the couples who volunteered:

For the next month, until November 17th, please pay particular attention to any unusual occurrences in your residence. These occurrences may be emotional feelings, physical sensations, or environmental events in your residence. Please keep detailed and accurate notes, even if you know or believe to know what caused the occurrences to happen. I will need the gender and age of adult occupants, and who had each experience noting. If you have children please do not discuss this with them. I have no desire to upset children! The types of unusual experiences I am interested include but are not limited to

* Visual – seeing things not there

* Audio – hearing stuff with no known cause

*Tactile – the feeling of being touched with no obvious reason

* Olfactory – strange smells

* Sensed “presences”

* Intense emotion for no apparent cause beyond that you might normally experience

* Object movements with no apparent cause

* erratic function of equipment.

Of the five couples involved in the experiment, only one of them reported no experiences of any kind that fell into the categories listed.  The other four couples all reported varying numbers of odd observations; one couple said that these had occurred in the family car, but not in the home, a finding that Romer's analysis excluded as it did not fit the methodology, but which still supports Romer's conclusion quite nicely.  The other three couples all reported a great many goings-on, with one recording 22 overall "unusual experiences" -- just shy of one a day.

What's most interesting about this study is that consistently, the test subjects reported higher and higher frequencies of "unusual experiences" as the month progressed.  Although in my opinion it's still a small data set to draw any kind of rock-solid conclusion upon, the relationship looks linear -- the number of weird things you notice seems to be directly proportional to the amount of time you've spent looking for them.  This, Romer concludes, "... may simply show the priming effect of participating in the experiment.  There is no reason to think the participants would have thought very much if at all about what occurred, let alone ascribed it to spooks, if they had not been participating in the diary study."  It's evident that these peculiar little events happen all the time, and most of them (rightly) escape our notice; but when we're forced to notice them, we do, and then the ones we notice increase our certainty that "something strange is going on," and the whole thing snowballs.  Romer writes, "... I have no doubt that life is full of tiny anomalies: during the day it has taken me to write up this replication my partner has texted to say she had her sat nav come on while lying on her bedroom floor and make her jump by telling her to “turn right”; I myself thought I saw Cuddles my black cat sitting on top of a cupboard, but on looking again he was not there, and was still sleeping in my bedroom when I returned to the computer."  We only ascribe meaning to them when we're primed to -- when enough of them occur in rapid succession that we're forced to pay them more attention, when we already thought our house was haunted... or when we're asked to notice them and write them down.  After that, positive feedback takes over.

It's the psychological component of our perception that always makes me suspicious of eyewitness accounts.  People act as if we're highly accurate recorders of what we experience, when in reality our attention is selective and our memories highly unreliable.  Odd, then, that eyewitness testimony is considered one of the highest forms of evidence in courts of law, isn't it?  What Romer's study does is to cast further doubt on our ability to discern what constitutes out-of-the-ordinary occurrences -- which makes me even more suspicious of most of the alleged evidence of hauntings.

On the other hand, the whole thing has made me wonder a little about the scraping noise I keep hearing up in the attic.  Wonder if I should investigate?

Nah.  I'm sure it's nothing.