Chat with us, powered by LiveChat How do we know that certain areas of the brain are specialized to do specific kinds of processing?? (There are multiple sources of evidence you could point to for this one.)? - EssayAbode

How do we know that certain areas of the brain are specialized to do specific kinds of processing?? (There are multiple sources of evidence you could point to for this one.)?


How do we know that certain areas of the brain are specialized to do specific kinds of processing?  (There are multiple sources of evidence you could point to for this one.)  Are there any practical implications that result from knowing what is localized where?


Ghostly appendages: What is phantom limb syndrome?  What does it tell us about neural plasticiity? (First, someone explain what plasticity is.)  On a more speculative note, how does the existence of phantom limb syndrome affect your own view of the relationship between mind and body?


Speed of neural transmission. This one is actually a demonstration activity as well as a question.  Please make sure that every subquestion (A, B, C, etc.) gets addressed by someone, but each person need only contribute to one of them to get credit.  Here goes:

A) Get a group of people together** [if that's not possible or advisable, see below] – at least 5, but 10 or more is better; it doesn't matter who they are. Also get a stopwatch.  Stand in a circle holding hands.  The person with the stopwatch should squeeze the hand of the person next to them and start the clock.  That person squeezes the next person's hand, and so on, until the stopwatch holder's other hand is squeezed and they stop the clock.  Do this an odd number of times (at least 5 times, more is better) and record all the times.  Then have everyone sit down and grab each other's right ankle with their right hand and do the same thing – record the times.  Post a list of your group's times here.

B) Look at the lists of times posted and find the median time for hand-to-hand and for hand-to-foot for each group that posted.  (The median is the number that has an equal amount of scores above and below it when sorted from least to greatest; it's the middle score.)  Post a list with the two median times for each group and the number of people who were in the group.

**NOTE:  If it is not possible or advisable to get a group of people together right now, skip parts A and B and use the following data to answer the other parts of this question.  Archival data from a group of 5 people who did each task 7 times:

Hand Squeeze

.85 Average

.75 Median

Right ankle with right hand

1.23 Average

1.26 Median

C) Take the list of median times and calculate the PER PERSON times for each group – the median divided by the number of people in the group – for both conditions.

D) Compare the median per-person times for the two conditions across all the groups:  hand-to-hand vs hand-to-foot.  (Extra credit if you go beyond calculating averages and do a t-test or something similar.)

E) Which was faster?  Why did that happen?

F) How fast do signals travel along neurons?  (Someone look it up and tell us where you found it.)

G) Estimate how far the signals traveled in the two conditions of this demonstration.  Were the observed times what you would expect based on how fast neurons transmit signals?  If not, what do you think might have caused the discrepancy?

H) When I have used this demonstration in a classroom, I have often used two additional conditions.  What do you think would happen in each of them, compared to the two conditions we tried, and why?   Here are the two conditions:

  1. Placing your hand on the next person's shoulder and squeezing their shoulder rather than their hand.
  2. Placing *both* hands on their shoulders, and alternating left and right.  So if your right shoulder gets squeezed, you squeeze the left shoulder, and vice versa.


First read the following case study of finding evidence on the internet: Homeopathy

This question is about homeopathy specifically, not alternative medicine or natural remedies in general.  Many people use "homeopathic" as a synonym for "natural."  That is not what we mean here.  Be sure you understand what a homeopathic remedy is.

Note that the main point of the case study is that homeopathic remedies, defined as extreme dilutions of toxins in water, can not be anything other than placebos because they would contain only water.  So (barring magic or the inclusion of some other active ingredient) we can be certain, even before doing any experiments, that homeopathic remedies have no physiological effects.  The question is if we did not already know that, how easy would it be to tell they don't work from doing a web search?

Do a web search on the word "homeopathy."  Discussion Part One: Is the information from the web search accurate?  If the only information you had was the sites returned on the first page of the web search, would it be easy to tell that homeopathic remedies do not work (other than as placebos)? Why or why not?  Discussion Part Two: How can you find accurate information? What information search strategies could help you be more likely to come to the correct conclusion, that homeopathic remedies do not work?



Some posts in the past have mentioned the alternative medicine practice known as homeopathy.  This topic is such a great example of how difficult it can be to find reliable information on the web that I thought it would be worth discussing in some detail.  Some questions this example can help us explore are: What sources of information are trustworthy?  What counts as “research” or as “evidence”?  When I encounter claims that “research” supports two opposite conclusions, how can I decide what to believe?

Homeopathy is a practice based on the belief that very tiny doses of a substance that causes a disease can be used to treat that disease.  A quick web search for “homeopathic arsenic,” for example, produced offers to sell me “30c” diluted arsenic tablets to treat stomach ailments.  Arsenic is a deadly poison which produces (among other things) violent intestinal disorders.  By the logic of homeopathy, a dilute solution of arsenic should, therefore, cure intestinal disorders.  How dilute?  The homeopathic designation of “30c” indicates that one part arsenic has been diluted with 100 parts water (C being the Roman numeral for 100) thirty times.  So after the first dilution it would be 1/100 arsenic.  After the second it would be 1/10,000 arsenic.  After 30 such dilutions it would be one part arsenic per 100^30 (100 to the 30th power) parts water.  That is a 1 followed by 60 zeroes, or 10^60, ten to the sixtieth power.  To give you a sense of how dilute that is, there are estimated to be about 10^80 atoms in the universe.  And a cup of water contains about 10^25 molecules of water (see for the calculation).  So one part arsenic in 10^60 parts water would be less than 1 atom of arsenic per cup of water, which is just… water.  Each of the “homeopathic 30c arsenic” tablets I could buy would probably contain zero atoms of arsenic if the contents are exactly what the label says they are.  

So if a homeopathic remedy is manufactured as advertised it would contain no active ingredients.  It would, in other words, be a placebo.  

Yet WebMD says that “Research is mixed. Some studies show that homeopathic remedies are helpful, while others don’t.”  (  What??  How can some studies have found that remedies containing no actual active ingredients are helpful?  Is that just an outright falsehood?  No, it is perhaps worse than that.  It is technically true but misleading.  There have indeed been some published studies that show benefits from homeopathic remedies.  But those studies are of poor quality (failing to effectively control for placebo effects or observer bias), and the best studies have consistently found no evidence that homeopathic remedies have any effect (see for useful summaries of the double-blind studies and meta-analyses that make this clear.  Useful summaries can also be found in  The UK's national health service also has a very good summary of homeopathic remedies in general:

The entire WebMD article on homoepathy appears to me to contain no statements that are individually technically untrue, yet as a whole the article gives the extremely misleading impression that homeopathy is a legitimate and perhaps effective medical practice.  Read the article and see if you can find examples of technically true but misleading content.  Here is one that really walks a fine line: “Doctors are divided because some of the theories behind homeopathy don’t line up with the principles of chemistry and physics.”  I suppose it is true that “doctors are divided” in that there probably are one or more medical doctors who believe in homeopathy.  And “some of the theories behind homeopathy don’t line up with the principles of chemistry and physics” is certainly true, but it makes it sound like there are minor quibbles with some peripheral parts of homeopathy, when in fact the primary theories of homeopathy are contradicted by the known laws of physics and chemistry.  

Homeopathy is a great case study for how hard it is to find reliable information.  It is hard to imagine anything that could be more obviously ineffective than what homeopathic remedies, by the definition of homeopathy, claim to be: substances that contain no active ingredients.  Barring magic or the inclusion of other active ingredients, it is not possible that homeopathic remedies could have any effect other than as placebos.  Yet there are published studies that seem to show evidence for their effectiveness, and well-known web sites that seem to give the impression that they are legitimate medical treatments.  If it can be this confusing trying to find reliable evidence about homeopathy, what hope do we have of figuring things out for less obvious questions?  What can you do?

First, try to get into the habit of thinking probabilistically.  When deciding what you should believe, remember that none of us knows everything, and not everything is known.  We have a natural tendency to want to classify things absolutely: definitely true or definitely false – 100% confident or 0%.  For most questions the most accurate answer for me is “I don’t know.”  And even for almost everything that I DO know I don’t know it to be true or false with 100% confidence.  Instead of saying “I believe X” or “I don’t believe X”, get in the habit of saying to yourself “I’m N% confident that X is true.”  I’m 85% sure that cognitive behavioral therapy is an effective treatment for anxiety disorders, for example.  I think there is only a 15% chance that Freudian psychodynamic therapy is effective.  I’ve read quite a bit about the research on both of those, the evidence is pretty clear in my view, and therefore I’m pretty confident.  For some therapy that I am unfamiliar with I might start out completely unsure: 50%.  Then, as evidence accumulates, I will change that probability up or down in proportion to how much evidence there is and how good it is.  Belief should be on a sliding scale, depending on the strength of the evidence.

Second, be disciplined about what you accept as evidence.  Empirical scientific research should be given some weight.  How much?  That depends on how many studies there are and how good each of them are.  The spacing effect and the retrieval practice effect in learning have both been repeatedly demonstrated in well-controlled experiments (see  I’m 99% confident in each of them.  Nutrition studies are mostly based on retrospective self-report data and correlational data, so even the things I most believe about nutrition (more vegetables and fiber good; more sugar bad) I’m only about 80% confident in.  And I have very little confidence in any individual new nutritional study I see reported in the news.  I will give it almost no weight until it has been replicated repeatedly and consistently.  

Correlational evidence from scientific research and self-report evidence from survey data should be given only limited weight. It is not as reliable as well-controlled experimental evidence (like double or triple blind clinical trials), and it takes longer to accumulate a convincing body of this kind of evidence.  

Personal experience, casual observation, and “stories” should be given almost no weight as evidence.  Following this advice is hard and takes self-discipline, because it is human nature to find anecdotal evidence to be the most persuasive.  How many people give up smoking because of statistics about lung cancer rates, versus how many give up smoking because a loved one who smoked died of lung cancer?  The individual story is more persuasive.  But individual stories can be misleading:  How many people have delayed vaccinating their child because they were frightened by a story from someone who said vaccinations caused their child’s autism, even though scientific studies have conclusively shown that vaccines do not cause autism?  

Third, try to identify sources of information that are generally trustworthy that you can use as a “reality check” when you encounter conflicting claims.  Government science agencies and scientific professional societies are usually more trustworthy; groups advocating for a particular idea or practice are more suspect.  Here are a couple of sites that I’ve found to be pretty reliable on a wide range of topics:

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