Archive for the 'Neuroscience' Category

Aug 14 2018

Phantom and Prosthetic Limbs

One of the goals of prosthetic technology (replacement limbs for amputees) is to make the user feel like the prosthetic is part of their body – that they own it and control it (called embodiment). It is more difficult to control a limb that does not feel like part of your body, and users need to visually look at a prosthetic to see where it is. This is true of passive prosthetics as well as robotic ones.

I have written previously about researcher attempts to provide sensory feedback to robotic limbs. A new study adds to this growing knowledge about how embodiment works and how to hack the brain to make it happen.

The key to embodiment seems to be multimodal sensory feedback. If the brain sees and feels the same action, that is all that is necessary for the “ownership module” to kick in – that part of the brain that makes you feel as if you own the various parts of your body. The most primitive manifestation of this is the rubber hand illusion. If you have a rubber hand protruding from your sleeve as if it is your real hand, and you see the rubber hand touched while your real hand is touched (and therefore you feel it), this will create the temporary illusion that the rubber hand is your real hand. Obviously this is not practical for everyday use of a prosthetic.

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Aug 02 2018

Prior Exposure Influences What We See

Published by under Neuroscience

One of the mantras on this blog is that perception is constructed by complex processes in the brain, not a passive recording of external stimuli. The implications of this are profound – what you see, hear, and taste are influenced by your internal model of the world, and what your other senses are telling you. In real time your brain is comparing your sensory inputs to each other, and to stored memories. It then finds the best match possible and (this is critical) tweaks your perception to more strongly conform to the apparent match.

In a very real sense, believing is seeing.

A new study extends our understanding of this constructive perceptual phenomenon a bit with respect to vision. The question was mainly – where in the brain are these processes happening with respect to vision? The researchers used a standard paradigm called Mooney images, which are black and white images degraded so that they are difficult to interpret. However, when primed with an undegraded grayscale version of the image (called disambiguation), it becomes trivially easy to interpret the Mooney image. The effects of this priming may last from days to indefinitely.

The researchers confirmed this priming effect, and that it is very robust. What this means is that what the subjects saw was determined as much, if not more, by their memories (of the disambiguation image) as by their current visual stimuli. What you remember is as or more important than what you are seeing, at least when what you are seeing is ambiguous.

The new information from this study, however, was what brain activity reflects this process. Here they also confirmed prior research that visual processing is very hierarchical – basic processing occurs at primary visual cortical levels, and then goes up to higher levels where more complexity is added and memory becomes a stronger influence. Specifically the researchers wanted to know if the default-mode network (DMN) was playing any role.

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Jul 30 2018

Eye Movements and Personality

Published by under Neuroscience

Have you ever seen someone with “shifty” eyes? How much can we really tell about someone from just their eye movements? This is an interesting question that researchers are exploring. A recent study uses artificial intelligence software to attempt to correlate eye movements of subjects during a specific task with standard measures of personality.

Let’s take a look at this study and then discuss what it all means. Researchers rigged 50 subjects with head gear to record their eye movements:

“Binocular gaze data were tracked using a state-of-the-art head-mounted video-based eye tracker from SensorMotoric Instruments (SMI) at 60Hz. The tracker has a reported gaze estimation accuracy of 0.5° and precision of 0.1°. The tracker recorded gaze data, along with a high-resolution scene video on a mobile phone that was carried in a cross-body bag.”

The data from eight of the subjects was not usable, so they were left with 42 subjects. They recorded an average of about 13 minutes from each subject with about 20% loss of data. They also gave each subject a standardized personality test, and then used an AI learning algorithm to correlate features of eye movement with outcomes on the personality test. They analyzed the data to see how much the eye movements “predicted” the personality traits, and found:

“…our classifier performs well above chance (that is, confidence intervals do not overlap with any of the baseline performances) for neuroticism (40.3%), extraversion (48.6%), agreeableness (45.9%), conscientiousness (43.1%), and perceptual curiosity (PCS, 37.1%). For openness (30.8%) and the Curiosity and Exploration Inventory (CEI, 27.2%) our classifier performs below chance level.”

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Jul 19 2018

Developing Cognitive Biases in Young Children

Published by under Neuroscience

I have discussed a number of cognitive biases over the years, based mostly on research in adults. For example, Kahneman and Tversky first proposed the representativeness heuristic in 1973. But at what age do children start using this heuristic?

A heuristic is essentially a mental short cut. Such short cuts are efficient, and decrease our cognitive load, but they are imperfect and prone to error.  In the representativeness heuristic we rely on social information and ignore numerical information when making probability judgments about people.

In the classic experiment subjects were given a description of the personality of a student, designed to be a stereotype of an engineer. They were then asked how likely it was that the student was an engineering student. Many subjects answered that the student was likely an engineering student, without considering the base rate – the percentage of students who are in engineering. Even when given that information showing it was unlikely the student was an engineer, many subjects ignored the numerical information and based their judgments entirely on the social information.

This can also be seen in the context of general cognitive styles – intuitive vs analytical (or thinking fast vs thinking slow – as in the title of Kahneman’s book). Intuitive thinking is our gut reaction, it is quick and relies heavily on social cues and pattern recognition. It is therefore fast, but is also error prone and subject to a host of cognitive biases.

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Jul 16 2018

Motivated Reasoning vs Lazy Thinking

Published by under Neuroscience

A new study takes another look at partisan motivated reasoning, with surprising (sort of) results. The study shows that as interested critical thinkers, we need to keep up with the psychological research about critical thinking.

First some background – motivated reasoning refers to the tendency to rationalize a defense of a position that we hold with some emotional investment, and reject counter-evidence. If a certain belief is part of our tribal identity, or has emotional significance, we react differently to relevant facts than when a belief is emotionally neutral. For neutral beliefs, we happily update what we believe when new credible information is presented to us. I don’t really care if Thomas Edison invented the light bulb or stole part of the design from Joseph Swan (he did, but he made important improvements also) – whatever the historical data says, I will happily believe. But if someone claimed that George Washington really wanted to be made king of America but was forced to accept a lesser role (he didn’t, I just made that up), I might be motivated to push back just out of patriotism.

Psychologists have been studying this phenomenon for years, and are discovering that it is a real thing, but it’s complicated (that should be no surprise). There is a general challenge with psychological studies that human behavior is complex and opaque, and they resort to using constructs and markers to reveal specific phenomena. How do you test motivated reasoning? First you have to separate people into groups based on some feature that should impact their motivation, such as ideology, religion, or political affiliation. Then challenge their beliefs and see how they respond.

Many studies have shown that when you do this, ideology matters. There is even a possible backlash effect, where motivated believers dig in their heels, but this effect is controversial and may be very small.

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Jul 03 2018

Defining Down Problems

Published by under Neuroscience

This is an interesting cognitive bias recently documented by psychology researchers – we tend to lower the bar for what constitutes a “problem” as the frequency of that problem decreases. The authors call this “perception and judgement creep.”

Let’s say you are a teacher tasked with documenting instances of “bad behavior” among your students. What constitutes “bad behavior” requires judgement, and occurs on a continuum. Does whispering to your friend when everyone is supposed to be quiet count? What the researchers found is that the frequency of behavior which can be considered “bad” determines where you set the cutoff. If the frequency is high, then you will likely count only really bad behavior. As the frequency drops, you will count less and less bad behavior as “bad”, which will create the illusion that the problem of bad behavior is not getting better, when it objectively is.

The researchers did a series of experiments with very different targets. In one experiment they had subjects count blue dots. They were shown dots with a variety of colors, some clearly blue, some clearly not blue, and others that were on the borderline of being blue, such as purple or violet. What they found was that as the frequency of clearly blue dots decreased the subjects started to expand the range of what they considered “blue”, including more purple dots.

In another experiment they had subjects look at pictures of faces and count how many were showing angry emotions. As the frequency of angry faces decreased, subjects started to count more and more neutral faces as angry. In a third experiment the researchers asked subjects to review research requests and look for unethical behavior. Yet again, when the frequency of clearly unethical requests decreased, the subjects started counting more and more innocent requests as unethical.

So what’s going on here? Like any such psychological research, it deals with complex human behavior and questions about cause and effect are very difficult to address. Much more research is necessary to flesh out the conditions of this phenomenon and to start to tease apart its primary causes. But let’s speculate about plausible causes.

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Jul 02 2018

Crow Intelligence

Published by under Neuroscience

Crows are really smart birds. Most people have probably heard this by now, but their intelligence continues to surprise researchers. A new study adds still more evidence for the problem-solving skills of these birds.

First, a little background on crows – they are members of the Corvidae family of birds, which includes crows, ravens, rooks, jackdaws, jays, magpies, treepies, choughs, and nutcrackers. This entire family of birds exhibit relative smarts, but crows and jays in particular have demonstrated surprising intelligence. Crows are one of the few animals to pass the mirror test – to recognize themselves in a mirror (actually this study was done on Eurasian magpiesin one study crows failed the mirror test), they can fashion and use tools, they have incredible memories, and exhibit impressive problem-solving skills.

The new study looked specifically at Caledonian crows. The researchers set up a “vending machine” that can be operating by putting a piece of paper of a certain size into a slot, which would then release a single treat. The crows quickly learned how to use the vending machine to get food. But that wasn’t the new bit – the new bit was that they then gave the crows paper, but not the right size for the vending machine. They also had no reference for how big to make the paper, they only had their memory of prior use.

The question for the researchers was – could the crows fashion the paper into the right size and shape for the vending machine purely from memory? They did, without any problem. The reason the researchers thought they could was because these crows already exhibit tool-making ability. They fashion hooks out of stems and use them for poke grubs or fish for food. They do this apparently from memory. Baby crows have also apparently learned this ability from their parents, which indicates the existence of a tool-making culture among these crows.

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Jun 29 2018

Free Will and Morality

Do we have real free will, and perhaps more importantly, what are the moral implications of belief in free will? These are interesting questions that are sure to prompt vigorous debate when they come up.

I have discussed the first question before, in which I take (shocker) a neuroscientific approach. From everything we know about brain function, our experience of our own existence, including what we perceive and the apparent choices we make, are largely a constructed illusion. Many times we feel as if we are making a conscious choice, but we can see in the brain that the choice was actually made subconsciously before we are even aware of it.

Even when the choice is made consciously, meaning we are aware of the factors that are affecting the decision, that does not mean we have truly free will. The brain is still a machine, and is dependent upon the laws of physics. A stone does not have free will to choose its path as it rolls down a hill. Its path is entirely determined by physics. Some argue that brain processes are no different, just orders of magnitude more complex.

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Jun 26 2018

Male and Female Brains Revisited

There is a seemingly endless debate about whether or not, and how, male and female brains differ. This is also an extension of the also endless nature vs nurture debate.

Unfortunately these questions get tied up with social, political, and ideological questions. I say unfortunately because they really shouldn’t be. Ideally we can ethically recognize that the optimal position is to respect every human’s rights and dignity. Everyone should be afforded the same basic rights and opportunity to pursue their potential and desires.

This ethical position can be valid even if it turns out to be true that not every human being is identical in terms of their potential or inclinations, or whether or not there are identifiable subgroups of people. These are scientific questions that should be approached and answered scientifically.

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Jun 01 2018

Another Advancement in Prosthetic Limbs

I have been following the development of brain-machine interfaces and their application to artificial (prosthetic) limbs. A recent paper documents another incremental but significant advance – combining a new surgical technique for amputation with a prosthetic designed to take advantage of it.

The goal is to close the loop between voluntary muscle control and sensory feedback, which is critical to that control. The way our brains normally work is to constantly monitor various sensory streams in order to create the subconscious and conscious sensation that we occupy, own, and control the various parts of our body.

We may take these phenomena for granted, but they are an active construction of the brain that are critical to proper function. Without the sensation that we occupy our body, we would have “out-of-body” sensations, like we were floating in space, and this would make it difficult to interface with the physical world.

Without the sense of ownership, we don’t feel like a limb is part of us, and it is therefore not incorporated into our internal model of our own body. This is the current state-of-the art for normal prosthetics – they feel like they are attached to the user, but not part of them. It therefore takes more conscious effort to use them, and control is not as good as a normal limb.

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