Troxler's Fading

Look at the little black cross at the center of this soft color field. Try not to move your eyes. Notice what happens to your perception of the colors in the rest of the area.

Did the colors mostly fade away to gray? It's caused by a neural adaptation that reduces your attention to a non changing stimulus. This happens because: 

"the neurons in the visual system beyond the rods and cones have large receptive fields. This means that the small, involuntary eye movements made when fixating on something fail to move the stimulus onto a new cell's receptive field, in effect giving unvarying stimulation."

 Source: Wikipedia on Troxler's Fading

Moving Objects Appear More Saturated

A recent study published in the Journal of Vision has shown how motion can alter our perception of color. According to the researchers, moving objects tend to appear more saturated than their stationary counterparts.

The study involved participants viewing a series of colored circles, some of which were stationary and others that moved at varying speeds. Participants were then asked to rate the saturation of each circle. The results showed that moving circles consistently appeared more saturated than those that were stationary, regardless of their actual color.

This finding might have applications for animators and for designers of digital interfaces.

Link to study "Visual motion perception"

The Hunt Effect

The Hunt effect is a phenomenon in which object colors at low light levels are perceived less saturated compared to those observed at higher light levels.

As this illustration demonstrates, a color's saturation appears to increase as the luminance increases. This effect can influence how we perceive color intensity on monitors with variable brightness levels.
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The Hunt Effect (Wikipedia)

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Honeybees Can Distinguish a Monet from a Picasso

Honeybees are good visual learners, and for some time it's been known that they can distinguish colors, shapes, and patterns. They can also recognize landscape scenes, flowers, and even human faces.

What are the limits of these abilities? Scientists constructed an experiment to test whether honeybees could recognize individual human artistic styles, such as the Impressionist paintings by Monet vs. Cubist or semi-abstract paintings by Picasso.

 

The findings show that they can learn to recognize and distinguish one style from another. They can generalize complex visual features even in images they've never seen before.

Given the relatively small size of the bees' brains, which weigh less than a milligram and contain just 960,000 neurons, the scientists argue that this appears to arise from a basic ability to "extract and categorize the visual characteristics of complex images" and is not a "higher cognitive function that is unique to humans."
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Scientific paper: Honeybees can discriminate between Monet and Picasso paintings

Related: Preference for and discrimination of paintings by mice

How Birds See Each Other

Many birds and insects have receptors for colors that we humans can't see. 

Starlings, for example, can see colors in reflected ultraviolet light that are beyond our human capacity. On the left is how starlings look to humans. On the right is how starlings may look to each other. 

Image credit: Klaus Schmitt 

According to Neringa Utaraitė: "Birds are tetrachromats, [so] they see four colors: UV, blue, green, and red, whereas we are trichromats and can only see three colors: blue, green, red. Bear in mind, that the magenta UV “color” shown here has been chosen to make it visible for us humans, it is a “false color”, as per definition UV light has no color."

Thanks, Massimo via Bored Panda

Does Language Constrain The Speed of Thought?

Here's a question: Are our thoughts limited by having to move at the speed of speech? 

And a bigger question: How is our mental life constrained by speech altogether?

These questions elicited a lot of lively discussion on my Instagram account. To the broader question, Rosemary reminded me of the truth and limitations of the Sapir-Whorf Hypothesis, also known as linguistic relativity, which argues that our thought is shaped by language we speak.

One problem with such a theory is that it tends to assume that all thought is verbal. Artists, musicians, architects, and engineers know otherwise. We can form purely visual or musical ideas which surely qualify as a form of thought or reasoning. If you've ever had an artistic encounter with another artist with whom you share no spoken language, you know that those visual ideas can be shared between people no matter what languages they speak.

Regarding the first question about the speed of thought, it occurs to me that when we are speaking, our language necessarily places upper limits on the pace at which we can roll out ideas, a problem for human-computer interfaces. An artificial intelligence can generate paragraphs in milliseconds, but it takes us a lot of time to type or say a series of ideas. 

Sometimes I have the opposite problem, where my brain works a little too slowly to articulate a sentence fluently, so the result almost sounds like aphasia. I believe that for most people, our receptive capacity for language by timing how fast you can read, or while listening to an audio book by doubling or tripling the normal speech velocity. You can demonstrate this on YouTube or your favorite podcast app by increasing the speed settings on audio playback. 

Certain non-linguistic modes of thought don't seem to be limited by velocity of expression. For example, the thought that goes into solving a Rubix cube seems almost like an instantaneous pattern recognition, and the act of puzzle solving appears to be limited only by the neuro-muscular action of the hands.

To me, the limitations of language become clearest when trying to translate a memory of a dream after awakening. Rendering a dream into words is like trying to taxidermy a jellyfish. The act of trying it makes me realize how words can do violence to certain kinds of non-logical ideas.

Bistable Percepts

Most people are familiar with the face / vase illusion (below). Psychologists refer to it as a "bistable percept." 

A bistable percept is an image that can be perceived in two different ways. The perception can switch back and forth between the two interpretations, but you only see one at a time. 


Another example of a bistable percept is the Necker cube which switches from appearing above you and projecting to the right, to appearing below you and projecting to the left.

One characteristic is that the duality, once perceived, can't be forgotten.

Ambiguous Images

Take a look at this picture. What do you see? When you look at it again, do you see something else?

Image courtesy Steve Stuart Williams and Tim Urban

Most people see a man, off balance, running into a snowy forest. Then after looking again, they see a dog running toward us. Some people see the dog first and have a hard time seeing the human.

What's going on is that there are two opposite streams of information processing going on in your brain. One stream is like a camera. Light enters your eye and resolves into shapes and patterns that move to the back of the brain and up through the cerebral cortex to higher level processing. 

But while this is going on, the brain is constantly generating theories of what it's seeing and delivering those theories down the pipeline, optimizing what you're actually seeing to fit its dominant conception.

All along you're reality-checking the top-down theory against the information coming up the pipeline from the eyes.

If the first top-down reading doesn't continue to fit the bottom-up facts, you start generating new interpretations.

A similar process happens with auditory processing when you hear a gunshot...or was that a firecracker?...or was someone popping a paper bag? You can feel your adrenaline surge when you think it's a gunshot, and all that changes when you realize it isn't.

Weird Science of Visual Perception

This was a cover feature I proposed for ImagineFX Magazine . They never used it, but I still believe it would be an awesome subject for artists. 

Birdman, oil. I used mainly four colors: viridian, permanent alizarin, yellow ochre, and cerulean.

Knowing about the science of eye-tracking, color vision, afterimages, and image processing helps us a lot as image-makers.

Read my previous posts on Visual Perception

The Role of Prediction in Perception

Stored Sunlight, 5 x 8 inches, watercolor and gouache

"The mind is a prediction engine, and nowhere is this more true than in visual perception." 

Comparison with photo taken after the fact

In his book "The Mind: Consciousness, Prediction, and the Brain," by E. Bruce Goldstein details current research about how the process of visual perception. 

What happens when we see is that the brain creates a top-down model of the world and continually checks it against the input coming from our senses.

"The mind encompasses everything we experience," he says, "and these experiences are created by the brain--often without our awareness. Experience is private; we can't know the minds of others. But we also don't know what is happening in our own minds."

This podcast interview with Goldstein lays out the issues well.

Attentional Spotlight

We bestow our visual attention very selectively, and that hierarchy of awareness is called the attentional (or foveal) spotlight. It's like exploring a pitch-black house at night with a narrow-beamed flashlight.

The fovea is the central spot of the retina, which is packed with photoreceptors, especially color receptors. In the peripheral retina there are fewer receptors, and they tend to be more responsive to tone and movement.

Robert Frederick Blum, Venetian Lacemakers, 1887, Cincinnati Museum

As I understand it, the attentional spotlight is more than just a structural feature of our photoreceptors. It also describes an aspect of our cognitive awareness of the world around us; some would say it's a central quality of consciousness itself. We focus our attention on elements of our world that match our conscious or unconscious search parameters, or distractions that pop up, competing for attention. 

Painters can capture the experience of the attentional spotlight, by helping the viewer know what's important, and downplaying the rest. It helps to darken, simplify, or blur areas that are less important. In the painting by Robert Blum, look at how much he downplays the peripheral areas in the foreground, and below the chairs, and keeps our attention within the circle of illuminated faces and hands.

Introduction to the attentional spotlight

Research Gate: Spotlight Model of Visual Attention 

Brain Scanners that Recognize What You Have Looked At.

In recent years, brain imaging studies have been able to recognize what image a person is looking at purely from brain activity. This is possible because the image maps onto the visual cortex almost like a blurry projection.

But now scientists have gone a step further. Researchers studying patterns of brain activity can correctly identify what image you have seen in the past, or even what image you're imagining, based on brain activity.

The research examines how you remember — and imagine— pictures that you've actually seen. It turns out that similar mechanisms come into play when you imagine something compared to how you process the real thing. 

The scanning system is still in its infancy, but it portends the kind of mind-reading device described by science fiction authors. "It's what you would actually use if you were going to build a functional brain-reading device," said Jack Gallant, a neuroscientist from the University of California, Berkeley.

CNN: Brain scans reveal what you've seen

Brain Inspired Podcast: Thomas Naselaris | Seeing vs. Imagining

Oscar Reutersvärd, Master of Illusion

Oscar Reutersvärd (1915-2002) has been called the "father of the impossible figure." 

He created many drawings that looked solid, but that couldn't actually be built in three dimensions.

One of his best known illusions is the impossible staircase, made even more famous by Roger Penrose and M.C. Escher.

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Oscar Reutersvärd on Wikipedia

How much data does the eye transmit?

Researchers estimate that the neural wiring from the retina transmits information to the brain at approximately the same rate as an Ethernet connection, about 10 million bits per second. That sounds like a lot, but it's not as much information as we think we're getting. 

"Much research on the basic science of vision asks what types of information the brain receives; this study instead asked how much. Using an intact retina from a guinea pig, the researchers recorded spikes of electrical impulses from ganglion cells using a miniature multi-electrode array. The investigators calculate that the human retina can transmit data at roughly 10 million bits per second."

"The retina is actually a piece of the brain that has grown into the eye and processes neural signals when it detects light. Ganglion cells carry information from the retina to the higher brain centers; other nerve cells within the retina perform the first stages of analysis of the visual world. The axons of the retinal ganglion cells, with the support of other types of cells, form the optic nerve and carry these signals to the brain."

As we've seen in previous posts, the impression we have of a highly detailed world don't come entirely from the eye, but also in a top-down fashion from in the form of predictive models from memory centers in the brain.

Read the article at Science Daily

A Funny Face

Have you seen this painting of Ada Lovelace, the Victorian lady who helped invent the computer? Her eyes are kind of close together, but you get the idea. The image was created by a computer.

Image courtesy Daniel Russell @danielrussruss

Now look at the image again. Do you see a dog with a white nose? Ada's eyes become the nostrils.

I found that once I saw the dog, I couldn't go back to Ada Lovelace again.

Most humans see the Victorian lady first. What does Google reverse image search think it is? Mostly it think's it's a dog, but there are some ladies mixed in, too. 

Pipeline of Meaning

Our eyes work with our brain to make sense of the world. 

At any given moment our conscious attention is fixated on one spot, but we're also guessing what's around it. This peripheral awareness cues the eyes where to jump next. That jumping or saltation happens about three times per second. 

By combining data from brain scans and eye-tracking, scientists at the University of Birmingham are trying to understand how we guess at what the next point of attention might be, and how different regions of the brain cooperate in this "pipeline of meaning" as "one object is established while another region of the brain is simultaneously deciding which next item is important."  

N.C. Wyeth (1882-1945), The Studio, ca. 1913-1915, oil on canvas, 16 x 20 1/4 in.

Collection of Mr. and Mrs. Frank E. Fowler. Photo Rick Rhodes

The scientists say: "Humans do not necessarily perceive objects simply one after another (in series), and nor do they perceive items simultaneously (in parallel). Instead, they establish a pipeline of observations, in which meaning from one object is established while another region of the brain is simultaneously deciding which next item is important."

A similar process happens when we read text. "The neuronal activity required to scan the next word in a sentence also increases according to the complexity of the word."

Read more: Our eyes and brain work together to create a ‘pipeline’ of meaning – new study

Outline vs. Tonal Shapes In Face Recognition

 Which is more important for face recognition: outline or tonal shapes?

Jim Carrey (left) and Kevin Costner.

According to vision scientists Pawan Sinha et al, "Images which contain exclusively contour information are very difficult to recognize, suggesting that high-spatial frequency information, by itself, is not an adequate cue for human face recognition processes." 

By contrast, the tonal shapes, even if they're out of focus, are relatively easy to recognize. The experts say: 

"Unlike current machine-based systems, human observers are able to handle significant degradations in face images." Shown here are Michael Jordan, Woody Allen, Elvis Presley, and Jay Leno.

That's why it's good to blur your eyes when you're capturing a likeness.

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Source: Face Recognition by Humans: Nineteen Results All Computer Vision Researchers Should Know About, Pawan Sinha, Benjamin Balas, Yuri Ostrovsky, and Richard Russell,

Sensor Fusion Problem

One of the mysteries of visual perception is how the information all binds together into a singular experience after raw sensory data is decoded. 

Light enters our retinas, and the optic nerve feeds information back to the visual cortex. After that, the signal follows neural pathways to various areas scattered throughout the brain.

For example, the dorsal stream interprets movement, while the ventral stream decodes information about shape, color and object recognitions.

In addition to the visual streams, other streams of sensory information arrive via sound and touch. Those signal pathways also appear distributed around the brain. 

For a long time, neuroscientists supposed that all the various streams of sensory impulses must converge or fuse together at a central location, but it doesn't happen that way. 

Given the scattered nature of that neuronal activity, how is it that we feel that our perception is a single experience? 

According to neuroscientist Jeff Hawley's new conceptual model of the brain, the various areas in the cortex arrive at a preliminary conclusion of what they're looking at. They appear to form a consensus in a manner very much like voting. To do that they don't need to be in the same place.

Read More:

Sensor Fusion on Wikipedia

A Thousand Brains: A New Theory of Intelligence by Jeff Hawkins

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Seeing Depth for the First Time

Neurobiologist Susan R. Barry was an adult when she acquired depth perception for the first time.

"Barry had been cross-eyed and stereoblind since early infancy. After half a century of perceiving her surroundings as flat and compressed, on that day she saw the city of Manhattan in stereo depth for first time in her life. As a neuroscientist, she understood just how extraordinary this transformation was, not only for herself but for the scientific understanding of the human brain. Scientists have long believed that the brain is malleable only during a "critical period" in early childhood. According to this theory, Barry's brain had organized itself when she was a baby to avoid double vision - and there was no way to rewire it as an adult. But Barry found an optometrist who prescribed a little-known program of vision therapy; after intensive training, Barry was ultimately able to accomplish what other scientists and even she herself had once considered impossible."

The story shows not only that the brain is malleable, but also that a conscious awareness of experience isn't the same as actually having that experience. As author Bruce Goldstein puts it, "Scientific knowledge is not enough." 

Susan Barry tells her story in her book Fixing My Gaze: A Scientist's Journey Into Seeing in Three Dimensions

Are Artists Right-Brained?

There's a lot of information online about the difference between the two hemispheres of the brain and what that means for artists.

Many commentators suggest that each of us is either a "left hemisphere person" or a "right hemisphere person," as if we think and act primarily with one dominant hemisphere. This idea originated from studies in the 1960s and '70s with patients whose two hemispheres had to be separated by cutting through the connecting nerve bundle called the corpus callosum.

The notion that has percolated through popular culture is that each half of the brain functions separately.

Recent studies reveal that the truth is actually more nuanced than that.

Iain McGilchrist, a psychologist who has investigated this topic, suggests that different hemispheres of the brain are actually engaged in similar cognitive tasks, but each half approaches that task in a different way.

The right half focuses more on the big picture, and the left hemisphere focuses more on the details. The right brain appreciates metaphor, poetry, humor, and music, while the left brain is more focused on the notes, the denotive facts, and the logical conclusions. 

Although they have somewhat different styles of information processing, the two hemispheres are both engaged as you navigate through most tasks, and they work together when you're creating a painting. 

In this YouTube video, which is illustrated by a whiteboard animation, Iain McGilchrist explains the lateralized brain, and how that affects our personal and cultural styles of thought. 

 

If you prefer podcasts, check out Iain McGilchrist's interview on NPR's The Hidden Brain.

The art teacher most strongly associated with this line of scientific reasoning is Betty Edwards, who wrote Drawing on the Right Side of the Brain and has updated it with a 4th Edition

 

Iain McGilchrist's book is called The Master and His Emissary: The Divided Brain and the Making of the Western World