Captain Psychology

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Perceptual Efficiency

Mirage

We share the same reality, sort of. It’s not that reality is shifting. Reality is consistent but our views vary.

Like people watching the same sunset, we are not standing in exactly the same spot so we see things from different angles, different perspectives.

Also, we are not equally gifted. As a person with low vision, my optical sensing system can perceive all the things you can. My images are out of focus, misaligned and poorly processed compared to what you see. You’re seeing digital hi def, I’m still watching VHS tape.

Sometimes it is not an equipment problem. With a mirage, don’t adjust your set; everything is fine. Mirages are not problems with sensation or perception. They are uncommon occurrences.

Our sense of reality relies on common events. Our systems don’t how to handle uncommon realities. In a superior mirage, you can see over the horizon because of the way light is bouncing. It’s odd so it is confusing to us.

There is a superior mirage in the Thomas Crown Affair (the newer one). Watch the sailing scenes. You’ll see New York in the distance. But the boats are much farther out at sea. The ghostly view of the city is a mirage.

It is just an extreme version of thermal inversion. Cold air is denser. More density, more refraction as light goes from warm to cold. Very hot air and very cold sea bends the light. If the bend is about the same as the curvature of the earth, you can see over the horizon. Perhaps this is how the Vikings discovered what was to them the New World.

In the desert, you get the other conditions. Cold air and hot sand give rise to the mirror images of an inferior mirage. Pretty but confusing.

Our sensing systems do really well most of the time. Our problem isn’t unique conditions. Our problem is the massive amount of information we intake. We have too much sensory input.

A related problem is we have too many receptors. Each eye has approximately 132 million photoreceptors. But there are only 1 million axons going to the brain. We need to dump a lot of data.

Here’s how we do it.

 

Four Principles of Efficiency

1. Separate Systems

We use two major nervous system. There is the central nervous system (CNS), which is composed of the brain and spinal cord. This system is isolated from the rest of the body and protected from disease by a restricting blood system (blood-brain barrier).

The peripheral nervous system (PNS) is everything else. The somatic system links the spinal cord to the body and organs. It is composed of the autonomic nervous system (ANS) which carries information to and from internal organs and glands.

The ANS is composed of the sympathetic nervous system (SNS) which arouses the body, and the parasympathetic nervous system (PNS) which quiets things down.

2. Separate Subsystems

Inside systems there are subsystems to handle specific functions.

In vision, the geniculostriate subsystem specializes on form and detail. The tectopulvinar subsystem tracks motion & location. You can lose one subsystem and still maintain the function of the other.

In audition, there are several subsystems, one for language, another for music and another for sounds. In touch, pressure and pain are separate. And in the brain, we have two cerebral hemispheres, each of which has several lobes for processing sensory information.

3. Ignore Steady State Information

Left footThis is a big one. If I ask you where your left foot is, your brain will hunt for it. You’ll move it to a new spot and the brain will say (metaphorically) call me is there is a problem. And then forget about it.

We feel clothes when we put them on, and watches and rings. But we forget about them. Constantly thinking about them would use too many resources, so we simply ignore steady state information.

 

4. Pre-Code for Critical Features

We have cells with specialized receptive fields. Each visual cell has a “hot zone,” a place which is more sensitive to stimulation.

Some cells respond to specific stimulation. There are “ on” cells which provide sustained firing when a light is on.  There are “off” cells which give a brief burst (transient) when a light goes off. And there cells that respond to up-down movement but don’t react to horizontal movement.

Pre-coding means less work for the brain.

 

Three Magnitude Mechanisms

1. Firing Rate

We reuse neurons to indicate when something is bright, loud or heavy. We just fire more often. As magnitude increases, so does firing rate. This works great up has a major limit. Neurons have to reset in order to fire again. They are quick but there is a limit of 1000 per second.

2. Volley Theory

When firing rate meets its limit, the body can have cells fire in a sequence. A whole group of cells can be fired in a swarm.

3. Summation

Cells can be wired to fire only when 100 or 1000 other cells have fired. This many-to-one wiring plan is another way to indicate magnitude. Similarly, other nerves can take over when signals are very strong.

 

Three Quality Principles

1. All Neurons Work the Same

The body is highly efficient. It doesn’t reinvent the wheel. It uses the same technology multiple times.

This has not always been obvious.

Johannes MüllerJohannes Muller proposed that perception is in the nerve. His Doctrine of Specific Nerve Energies states that vision nerves, touch nerves and hear nerves have unique qualities specific to that nerve. Vision nerves can only carry visual signals. The starting point doesn’t matter and the ending point doesn’t matter. The nerve itself if special.

It took nearly 90 years for researchers to show that all neurons work the same. Visual nerves don’t carry little images, they carry electrical signals. Hearing nerves don’t carry sounds, they too are electrical. It is not the nerves that are special. It is where they come from and where they go. Nerves are all the same: electrical.

2. Specificity

All nerves work the same but receptors are different. There are specific receptors for specific sensations. Pacinian corpuscle report deep pressure. Markel’s report light pressure.

Similarly, visual receptors have different jobs. Rods do target detection, work in low light, and black-white low res images. And there are three kinds of cones.

3. Across-fiber pattern theory

Perception can also utilize patterns of activity across many receptors. Taste is not one cell. Thousands of cells on the tongue are reporting at the same time. Similarly, color is the result of cone combinations. It’s teamwork.

 

3 Summary Principles

1. Correspondence between physical and psychological reality is NOT one-one

We use sensations to approximate reality. We creat a map of the environment, not an actual copy. We are not interested in sensations themselves. We care about what they mean. Some changes in light we ignore, other changes we track. Our goal is understanding the world around us, not copying it.

We are interested in relative height, relative weight and relative speed. We are not good at guessing how we are traveling, particularly if we are not close to the ground. We are great at detecting which of several cars is going fastest, even if we can’t tell how fast it is. We can’t use our hands as scales to give a precise value of weight but we can tell which hand is holding an apple and which is holding a lead ball.

2. Sensation and perception are adaptive

Another example of relative judgment. We judge brightness and color by its context. A gray square on a white background looks different when on a black background. A red object on pink, white or blue is viewed differently. We are not absolutists. We don’t waste the brain power. Relative judgments are just fine.

3. Sensation & perception are active processes

Here are some example of top-down processing. We are not passive receivers. The are actively looking ahead and deciding what we are seeing. We have perceptual rules we follow.

Stroop effectWe are subject to mental sets. Once we have solved a problem one way, we use that technique repeatedly, even if a simpler solution is available. A mental set is like a mental habit.

In the Stroop Effect you are asked to read a series of color words written in their appropriate colors. Red is written in red, blue in blue, etc. we do fine with this task. No problem. Then you are asked to say the color of the word, not the word itself. The catch is red is written in blue, etc. You quickly discover you stumble over these words. Your brain is primed to process words, not identify colors. We can identify the colors as long as we go slowly but we are struggling against our brains.

Let’s take a look at vision.

 

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‘There are two great principles of psychology: people have a tremendous capacity to change, and we usually don’t.”   Ken Tangen