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WHY DO I FORGET THE REASON I WALKED INTO THE ROOM?

This brain fart is so common it even has its own name: the 鈥渄oorway effect鈥�. Intrigued by this frustrating experience, at the University of Notre Dame, Indiana, and his colleagues asked people to navigate a virtual environment. Occasionally the participants would pick up an object, causing it to disappear from view. Now and again they would be asked what they were carrying. If they had moved into a different room, they were . Radvansky repeated the experiment in genuine rooms and found the same thing: people鈥檚 powers of recall are worse after they pass through a doorway than when they walk the same distance within a room.

What鈥檚 going on? As we move around the world, our brain is thought to construct what Radvansky calls a temporary 鈥渆vent model鈥� of our environment and our thoughts and actions in it. But storing several event models at once is inefficient. 鈥淣ew environments may require new sets of skills, and so it is best to focus our memory on what is currently at hand,鈥� says Radvansky.

Doorways seem to trigger the replacement of one event model with another. This swap makes us more likely to forget what happened in the first room. It鈥檚 not just doorways that trigger this shift 鈥� passing from rural fields into a town can do it too, or from highways to backstreets, upstairs to down.

WHY DO RANDOM NOISES TURN INTO WORDS?

Is it just me or does my printer say 鈥渃old feet, cold feet鈥�, every time it turns on? This strange perception actually hints at something fundamental about the way the brain creates our whole reality.

The world around us bombards us with sensory information. The brain doesn鈥檛 process every little detail 鈥� that would be very inefficient. Instead, it makes educated guesses.

When it comes to sound, the primary auditory cortex processes the rawest elements, such as pitch. Higher brain regions further up the chain process more complex features such as melody and meaning.

But rather than every detail being relayed up, the brain takes the rudimentary elements and combines them with memories and experience to make a prediction of what you might be hearing.

That prediction passes into the frontal lobes, which perform a kind of reality check. If that judges it to be sensible, we consciously perceive the sound. If not, then the information is sent up to the higher regions, which adjust subsequent predictions.

Because of the way the brain fills in these blanks, neuroscientist , UK, calls our reality 鈥渁 controlled hallucination, reined in by our senses鈥�. Indeed, when this goes wrong and the brain鈥檚 predictions are no longer kept in check, people can experience hallucinations.

As for my printer moaning about cold feet, what was once random noise must at some point have reminded my brain of the words 鈥渃old feet鈥� 鈥� perhaps it was its pitch or rhythm, or maybe I had cold feet at the time. Whatever it was, my frontal lobe gatekeeper deemed it an acceptable prediction and it floated into my consciousness. Once I had spared some conscious thought to my printer鈥檚 chatter, my brain had even more information on which to base future predictions. Now, it鈥檚 hard not to hear these words every time the machine switches on.

You can test this out for yourself. Listen to sine-wave speech, a sonically degraded version of speech (visit the online version of this story for an example). All you will hear is beeps and whistles. But if you listen to the original recording and return to the degraded version, suddenly you will be able to make out what is being said. Nothing has changed apart from your brain鈥檚 expectations 鈥� it now has better information on which to create your reality.

WHY DOES STARING AT A WORD TURN IT TO NONSENSE?

Coffee. Coffee. Coffee. Read a word enough times and not only does the spelling seem impossible but the word starts to lose meaning. This peculiar feeling was . Fixate on a printed word for too long, they wrote, and 鈥渋t will be found to take on a curiously strange and foreign aspect鈥� sometimes making it look like a word in another language鈥� or a mere collection of letters.鈥� The phenomenon was later named semantic satiation by psychologist .

This well-studied form of mental flatulence is thought to be a result of 鈥渃ellular fatigue鈥�. When a brain cell fires, it uses energy. It can usually fire a second time immediately, but if it keeps on firing it eventually tires and must take a short break to do so again.

鈥淩eality is a controlled hallucination, reined in by our senses鈥�

When we read a word over and over, the brain cells responsible for processing all aspects of it 鈥� its form, meaning and associations 鈥� tire. And so the word stops making sense.

To prove this theory, Jakobovits James and his colleagues had students repeatedly read and speak words and numbers two or three times a second for 15 seconds. They were then asked to rate how meaningful they were on a scale, either straight away or after reading or speaking a different word or number. The numbers and words after continuous repetition, but increased in meaning after a short interruption.

Some words are more conducive to the illusion. More meaningful or emotional words, such as 鈥渕assacre鈥�, for instance, may take longer to appear alien because your brain cycles through several different associations that it attaches to the word before fatiguing completely. A less evocative word such as 鈥渃offee鈥� may take only a few repetitions to turn into gobbledygook.

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HOW CAN YOU SUDDENLY FORGET YOUR PIN?

They are a handful of simple digits you鈥檝e been using on autopilot for years鈥� and then one day at the ATM, all of a sudden you get your PIN wrong. To make matters worse, the harder you try, the more remote those magic numbers feel. How can something so familiar just vanish?

Our memories are thought to live at synapses, the gaps between neurons where electrical impulses jump from one cell to the next. Each firing strengthens the connection between the pair of neurons concerned, making any further activity in the first neuron more likely to stimulate the second. For instance, if we think about an image of a flower and its name, the network of neurons responsible for those two concepts will activate and strengthen. When we later recall the image, the flower鈥檚 name is now more likely to be retrieved at the same time. This is the foundation for how we store information long term, such as our PIN.

Besides serious illness, there are two main reasons why our memories occasionally fail us. Connections between neurons weaken over time if not frequently activated 鈥� by recalling the memory, for example. This may be why your PIN occasionally flies out of your head; perhaps you just haven鈥檛 used it in a while.

The other reason is interference. When we recall a memory, it also becomes malleable and prone to change. In the case of the forgotten PIN, you may have used those numbers in some other way, mixing up the digits to create a new online password, for example 鈥� replacing the original number in your mind. Or perhaps you recently received a PIN for a new card. The memory of your original PIN has been contaminated with new information.

Your frame of mind could also be to blame: stress, in particular, is known to flood the brain with chemicals that can mess with memory. But it鈥檚 unlikely that a number you use as often as your PIN has left your memory bank completely, so take a break and try again later.

If that fails, try to recall your PIN using visual imagery 鈥� the line your finger usually takes to type it on the keypad, for instance. Studies have shown that associating things we want to remember with images makes them easier to recall.

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WHY IS THE DOOR HANDLE SMILING AT YOU?

Kate Middleton recently turned up in a jelly bean, and Jesus has appeared in everything from a to a .

Seeing faces in inanimate objects is a well-known phenomenon called pareidolia. You鈥檝e probably experienced it yourself, in the form of the man in the moon. Even monkeys get it. But why?

Our brain is primed to see faces from an early age. Fetuses can recognise the shape of a face from inside the uterus 鈥� scans show that they turn towards dots of light shone into their mother鈥檚 belly that resemble a face, but ignore random shapes.

鈥淔etuses can recognise a face from inside the uterus鈥�

To investigate pareidolia, at the University of Toronto, Canada, scanned people鈥檚 brains while they watched clips of random static. He told them that half of the time a face would appear.

Despite this being untrue 鈥� the screen always displayed static 鈥� participants a face a third of the time.

During the task, regions at the front and back of the brain involved in memory, planning and decision-making appeared to cause activation of the right fusiform gyrus, our face-processing region.

We know that the brain makes predictions about what we might see on the basis of prior knowledge (see 鈥淲hy do random noises turn into words鈥�).

The fact that the right fusiform gyrus becomes active suggests that the expectation of seeing a face is priming the brain to create one from even the most minimal information.

But why do we see faces even when we鈥檙e not expecting to?

Evolutionarily, it makes sense for the brain to be on high alert for faces. We need to be able to detect one and understand its motives 鈥� whether it is friend or a foe 鈥� in order to react.

That we are occasionally too good at it, spotting a screaming banshee in half a pepper or the Virgin Mary in grilled cheese is of little consequence compared with failing to spot a face hidden in the woods.

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WHAT CAUSES FREUDIAN SLIPS?

In 2012, CBS news anchor Robert Morrison referred to Prince William as the 鈥渄ouche of Cambridge鈥� rather than the duke. It was an unfortunate slip of the tongue, but did it reveal any private opinions about William?

Freud would have said that Morrison鈥檚 slip gave away his thoughts, but there could be a more forgiving explanation. When we speak, the brain calls up numerous areas 鈥� networks that consider all the possible word choices, those that process meaning, and those that help us form individual sounds. With all this processing going on, the brain occasionally makes a mistake, failing to suppress an alternative choice of word or activating the sounds for one word instead of another.

I mean goxi furl

Sometimes an entirely inappropriate word pops out, as when you call your boss 鈥渕um鈥�. This can happen because the word shares some context with the one you intended 鈥� your boss might look like your mother, or their names may both trigger the idea of an authority figure. As the brain shuffles through these associations to come up with the right word, once in a while it trips up.

鈥淚 used to constantly tell my class about piss and stretch when I was supposed to be talking about pitch and stress,鈥� says , emeritus professor of communication at the University of California, Davis. The linguistic blunders we make are non-Freudian on the whole, says Motley. 鈥淭hey are simple conflicts between different word choices.鈥�

That said, there is some evidence to support Freud鈥檚 ideas. In 1979, Motley鈥檚 team asked groups of heterosexual men to read pairs of words silently to themselves until a buzzer sounded, at which point they were told to read the words aloud.

One group had been greeted by Motley, a middle-aged man at the time. Another group was met by a good-looking, provocatively dressed young woman. 鈥淲e wanted to influence what their thoughts might be,鈥� says Motley.

They found that the men all made the same number of slips, but in different ways. The men greeted by the woman , reading 鈥済oxi furl鈥� as 鈥渇oxy girl鈥�, for instance. So on occasion, our thoughts do seem to influence our linguistic stumbles. Maybe there was more to Morrison鈥檚 slip up after all.

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WHY DOES A RECORDING OF YOUR VOICE MAKE YOU CRINGE?

When we speak out loud we hear our voice in two ways. The first is just as others hear us 鈥� via sound waves that make eardrums vibrate. The other is via vibrations that originate in our vocal chords and travel through the skull to our eardrums. Both sets of vibrations are transferred into nerve signals that are combined and then processed by the brain to give you an impression of what your voice sounds like.

However, as the vibrations from your vocal chords travel through your skull, they spread out, which lowers their frequency and leads to the impression that they are lower in pitch. When you hear your own voice on a recording, you hear its true pitch 鈥� which isn鈥檛 the sound you have spent your whole life hearing. That鈥檚 when most of us realise we have a squeakier voice than we previously thought.

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WHY DOES BAD NEWS MAKE ME BURST OUT LAUGHING?

As faux pas go, it鈥檚 pretty awkward. In the middle of a row, or when someone tells you some terrible news, the only thing you can do is laugh.

One possible reason for your apparent gaffe is that laughter acts as a social glue; it tells the people you are with that you like them and think like them. So an urge to laugh in the middle of an argument may just be an innate way of defusing the situation.

A study of macaques found that young animals would often of laughter and smiles when they felt threatened by a dominant partner. This was accompanied by submissive behaviour, interpreted as the macaques trying to express that they wanted to avoid conflict.

Neuroscientist V. S. Ramachandran at the University of California, San Diego, has another explanation for nervous laughter. 鈥淭he rhythmic staccato sound鈥� evolved to inform our kin who share our genes: don鈥檛 waste your precious resources on this situation; it鈥檚 a false alarm,鈥� he writes in his book, A Brief Tour of Human Consciousness. Perhaps, he says, nervous laughter is a protective mechanism, a way of convincing ourselves and others that a situation is not as bad as we might think and therefore guarding against anxiety from the news and stopping it from being too debilitating.

So next time you laugh inappropriately, don鈥檛 worry that you鈥檙e a black-hearted buffoon. Just blame your overprotective brain.

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HOW CAN SPEECH ON A LOOP TURN INTO SONG?

In 1995, was editing her spoken introduction to a CD about musical illusions when she left a recording of the phrase 鈥渟ometimes behave so strangely鈥� playing on loop by accident. 鈥淚 had been working on something else when I heard it,鈥� she says, 鈥渁nd wondered why it was being sung rather than spoken.鈥�

Deutsch, a psychologist at the University of California, San Diego, later tested the illusion by playing groups of people the same segment of speech 10 times. As it looped, the speech either stayed the same, changed in pitch or had its syllables jumbled. Only when the speech stayed the same did it gradually sound like it was being sung. To verify this effect, Deutsch asked another group to listen to the phrase 10 times and then repeat it back. Combining recordings of their voices showed that they were singing the spoken words to the same rhythm and tune.

Deutsch says that because pitch isn鈥檛 a crucial feature of the English language, the areas of the brain that deals with it are inhibited to some extent, perhaps to allow the listener to focus on more essential aspects such as vowel sounds and meaning. When speech is repeated, however, she thinks those brain areas are disinhibited, so the pitch features become enhanced and the whole phrase sounds more like music.

Although this illusion works with any phrase, Deutsch鈥檚 particular example 鈥� 鈥渟ometimes behave so strangely鈥� 鈥� seems to work better than others. 鈥淚 think it might be because it also has a similar pitch pattern to the chimes of Big Ben, and the same rhythm as Rudolph the Red Nosed Reindeer,鈥� she says. 鈥淲hen you put them together, the mind creates the idea that it is a song, not speech.鈥�

This article appeared in print under the headline 鈥淎bsent minded鈥�