4.1: Two Sides of the Coin: Sensation and Perception
The visual illusions in the video are powered by sensation and perception.
It became obvious that the anamorphic drawings were nothing more than flat two-dimensional drawings when viewed from different angles.
Sense and perception allow us to pick up signals in our environment and then we can assemble them into something meaningful.
Our perception of the world around us is often assumed to be perfect because of our sensory systems.
These beliefs are called naive realism.
One way that we can make sense of our confusing and chaotic perceptual worlds is by filling in information about the objects we see on a daily basis.
This process can occur without our knowledge.
The pixels that participants used to perceive images were often located next to regions where there was no sensory information, demonstrating that we use available sensory information to make sense of what's missing and thereby identify incomplete objects.
We often blend the real with the imagined, going beyond the information given to us.
We simplify the world by doing so and make better sense of it.
The basic principles apply to all senses.
Our brain picks and chooses among the types of sensory information it uses, often relying on expectations and prior experiences to fill in the gaps and simplify processing.
In this chapter, we'll look at some of the errors in perception depicted in the video at the beginning of the chapter.
They show us the parts of our brains that work for us.
We will discover how our sensory systems transform physical signals in the outside world into neural activity in the inside world.
We'll look at how and when our brains flesh out the details, moving beyond the sensory information available to us.
Our senses allow us to see majestic scenery, hear glorious music, feel a loving touch, and taste wonderful food.
When we first detect a stimuli, it's the best for all of our senses.
Unless it's an extremely hard seat or worse, we don't notice it after a few seconds.
The level of responding activation is the greatest when there is a need to conserve energy and attention.
If we didn't engage in sensory adaptation, we'd be watching everything around us all the time.
Many researchers focused on sensation and perception in the 19th century when psychology was distinguishing itself as a science.
A landmark work on perception was published by Fechner.
Imagine that a researcher puts us in a quiet room with a pair of headphones on.
She wants to know if we've heard one of the faint tones.
50 percent of our sensory systems are time sensitive.
On a clear night, our visual systems can detect a single candle.
The salamander's exquisitely sensitive Sniffer can detect a smell from as few as 50 airborne odorant molecules, and only one such molecule.
The JND is relevant to our ability to distinguish between stronger and weaker stimuli.
Imagine we're playing a song on an iPod, but the volume is turned so low that we can't hear it.
The amount of light generated by one candle standing one foot away is equal to the amount of light generated by the stronger stimulus.
Weber's law states that the brighter the light, the more noticeable the change in brightness is.
Imagine how much light we would need to make a difference.
We would need a lot of light in the first case and a little in the second.
Our friend can easily understand us without shouting.
They're uncertain when it's sunny.
They were able to account for participants' response biases.
We can measure how biased participants are when they respond "yes" or "no" with false-negatives and false-positives.
If you notice phosphenes when you rub your eyes after waking up, you can get a sense of this principle.
Many phosphenes look like sparks, and some look like multicolored shapes in a kaleidoscope.
Some people think that phosphenes may explain some reports of ghosts.
Different areas of the cerebral cortex are devoted to different senses.
Our brains respond the same way.
Table 4.1 Distinguishing Signals from Noise is when our visual sense receptors send it.
True positives, false-negatives, false-positives, and true negatives are part of signal detection theory.
The brain interprets the signals to the cortex as visual regardless of how they were stimulated in the first place.
Vision areas, hearing areas, and so on are all connected to corti V cal areas in the cortex.
Scientists have found many examples of cross-modal processing that produce different perceptual experiences.
The effect shows that our brains calculate the most probable sound from the information we get from the two sources.
The McGurk effect is when you hear the audio track of one syllable spoken repeatedly while seeing a video track of a different syllable being spoken.
The brain's best guess at integrating the two conflicting sources of information is this third sound.
An illusion that shows how our senses of touch and sight interact to create a false perceptual experience is another fascinating example.
This illusion involves placing a rubber hand on top of a table with the precise positioning that a participant's hand would have if she were resting it on the table.
The participant's hand is placed under the table.
A researcher strokes the participant's hidden hand and rubber hand with a paintbrush.
The rubber hand seems to be his or her own hand when the strokes match.
The effects may reflect "cross-talk" among different brain Ruling Out Rival Hypotheses regions.
In some cases, a single brain region may serve double duty, helping to process multiple senses.
Important alternative to sound also responds weakly to touch.
The findings perception in the somatosensory cortex are enhanced by visual stimuli.
There are a few types of synesthesia presented in Table 4.2.
A person feels the same sensation as another person.
Words are associated with tastes.
Sounds can cause strong emotions such as anger or fear.
Numbers, letters, and days of the week have personality characteristics.
The number 6 might be seen as a king or a sorcerer.
Mental maps are imagined as numbers.
Some numbers, dates, and months are seen as being closer or farther away in space.
No one knows how common synesthesia is.
Most of us see the top image less than 1 in 2,000 people, according to an early estimate.
Some grapheme-color synesthetes who "see" 500 British university students estimated the prevalence to be about 4%, implying that certain numbers as colors, might not be as rare as once thought.
Some scientists questioned the authenticity of synesthesia in the past, but research Synesthesia makes it much easier to show that the condition is genuine.
The visual cortex is active during perception, thought and language.
Journal synesthesia experiences are associated with brain activity.
Flexible attention is critical to our survival and well-being in a world where our brains are immersed in a sea of sensory input.
To zero in on a video game we play in the park, we must ignore the dust on our shirt, the shifting breeze, and the noise of the neighborhood.
At any time, we must be prepared to use sensory information to detect a potential threat.
We are well equipped to meet the challenges of our rich environments.
We can pay attention to important stimuli and ignore others with the help of this mental filter.
One message was delivered to the left ear and the other to the right ear.
Broadbent asked participants to ignore the messages that were delivered to one of the ears.
Participants are asked to repeat the messages they heard in order to replicate the findings.
I saw the girl if the attended ear heard it.
When we're not aware of it, the process of selecting one sensory mation is still being processed at some level, ignoring or minimizing even when we're not aware of it.
We don't notice what other people are saying unless it's relevant to us and then we perk up.
The finding tells us that the brain's filter, which selects what will and won't receive our attention, is more complex than just an "on" or "off" switch.
If it sees something significant, it's ready to take action.
We are going to read your mind.
Go back and read the next paragraph.
We're not good at detecting stimuli in plain sight when our attention is elsewhere.
Try it and see if you like it.
The "ESP trick" was adapted from a demonstration by Pickover.
You have to recal one of the six cards.
You can help remember it by repeating its name loud.
You should turn to page 128 if you're sure you have the card.
A woman dressed in a gorilla suit walked across the scene for a full nine seconds in the middle of the video.
Half of the viewers failed to notice the hairy misfit even though she paused to face the camera and thumped her chest.
We often need to pay close attention to the dramatic changes in our environments.
Change blindness is a particular concern for airplane pilots, who may fail to notice another plane taxiing across the runway as they're preparing to land.
Industrial/organizational psychologists are working with aviation agencies to reduce the incidence of this problem.
Eighty-three percent of the 24 radiologists who did the lung nodule scans failed to notice a gorilla image with a white outline that was inserted in the final case in a series.
The gorilla image in this photograph was 48 times larger than the average nodule and it was all the more impressive because it was about the size of a matchbook.
The experts were better at detecting lung problems than the untrained Journal Prompt observers.
Many car accidents are caused by change blindness.
Different parts of our brains process different aspects of an apple.
We don't really know how our brains combine disparate pieces of information into a unified whole.
An apple looks red and round, tastes sweet, and smells like an apple.
One of its characteristics is not an apple or even a part of an apple.
Many aspects of perception and attention can be explained by binding.
When we see the world, we rely on shape, motion, color, and depth cues, each of which requires different amounts of time to detect.
We'll discuss the different senses we rely on to make our way in the world, starting with the visual system.
The psychological mechanisms of reality-bending illusions will be untangled by this science.
Magicians can give their secrets to researchers and contribute to our understanding of perception.
"The hand is quicker than the eye, and the ability of stage magicians to create mind-blowing stunts involving sleight of hand" is a saying that many of us have heard.
Most magic tricks are carried out at a normal speed.
Consider the following example.
A magician can get peo rings off their fingers.
He accomplishes these feats by misdirecting their attention by coming close to believe that a coin has disappeared after it's seemingly trans to them, often touching them in multiple places other than where the ferred from his right to left hand was.
The researchers concealed the coin in the right hand.
The magi Robbins to discover the neuroscience behind how he pulls off his stunts, cian takes advantage of a little-known fact: viewers don't consciously have determined that people are more likely to follow the motion of his register information for a smal fraction of second after it arrives
Less than a third of the participants said the ball appeared to be in the left, because the onlooker's visual neurons keep firing for one-hundredth of a second after the coin is transferred.
The trick depended on the direction of the observers.
Stage magicians trick people by other means, such as how mental predictions and expectancies, rather than reality, affect by misdirecting attention and awareness.
The technique fools us.
Here's how it works.
The magician because we're consciously aware of and attend to only a tiny part of throws two bal s into the air, one at a time, and catches each in his the information that enters our eyes.
His head and eyes are focused on the flight Rensink, O'Regan, & Clark.
The bal was riveting the audience's attention.
The third time, the magician pretends to throw the bal, to a grand theatrical movement, such as pulling the rabbit but secretly palms it in his hand as he moves his head up to fol ow out of a hat, the performer distracts onlookers from noticing a less the imaginary.
In one study of this il usion, there was obvious movement related to a secret prop that was essential to the next two-thirds of the watchers.
Next time you see "The Fabulous Fabrini", leave the magician's hand and disappear in mid-flight.
In a second performing captivating feats of magic on stage or screen, don't be condition, rather than move his head to follow the flight of the imag surprised if scientists are studying him to sleuth how attention, aware inary bal, the magician looked at the hand that concealed the bal