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The Placebo Effect: Do You Believe Your Teacher?

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Teacher's Notes

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Although the placebo effect isn’t mentioned much in the classroom, it’s a fascinating subject delving deep into the human mind. It also gives students an idea of factors to be taken into consideration when working as a scientific researcher….or even in clinical trials!

This lesson will introduce students to the placebo effect and how it can influence scientific experiments. The experiment will involve measuring the reaction times of a control group, a group who believe they have taken a stimulant and a group who have taken a stimulant. The activity could last between 30-60 minutes, depending on how many experiments are carried out.

You may not want to mention the word “placebo” right at the beginning, so as to not give the game away up front.

Aim:

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To uncover the placebo effect in your classroom

Learning objectives:

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  • To understand that measuring the physical effect of a drug can be influenced by psychological factors.
  • That scientists need to take this into account when collecting evidence on the effectiveness of a drug.
  • To understand the need to collect accurate measurements and to analyse data and present it in a graphical form and identify patterns.
  • To describe the placebo effect.
  • To consider the other factors that might limit the reliability of the results.
  • To work effectively as a team.
  • To model the job of a medical researcher.
  • To evaluate an experiment and suggest improvements.

Learning outcomes:

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  • All students will learn that stimulants such as caffeine can speed up reactions.
  • All students will be able to measure pulse rate accurately.
  • All students will be able to carry out an experiment that will mimic a doubleblind trial.
  • All students will work well as a team.
  • All students will be able to draw graphs.
  • Most students will believe taking a drug can influence your body.
  • Most students will be able to identify dependent and independent variables.
  • Most students should be able to identify patterns in results and identify when these results do not follow the expected pattern of scientific results.
  • Most students will know what researchers do to minimise the placebo effect.
  • Some students will see the link between the classroom experiment and the real world of medical research.

Resources:

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  • Orange juice/Lemonade/Water (control)
  • Decaffeinated cola*
  • Caffeinated cola*
  • Clean drinking cups
  • 1 metre rulers
  • Stopwatches

(*can use Diet versions of the drinks, so as to not promote unhealthy lifestyles!)

Depending on how many lessons are run on this topic, students may need to be supplied with results collected from the previous lesson, resources on the placebo effect, and sheets to record their results on (or access to a computer to input their results directly into a spreadsheet). Examples of student sheets are provided with this activity.

Tests to monitor the effect of caffeine on the students:

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Simple tests (see “Tests to Do” sheet) include a reaction test (metre-rule drop) and a memory test or by a selection of objects presented to the class (as in Kim’s game). Students have a set time (one minute or less) to memorise as many objects as possible. After one minute they have to recall as many as possible.

Other tests are the following online ones, totally up to you which ones to do, and how to monitor the results (before and after drinking caffeinated drinks!)

Reaction time tests:

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Memory tests:

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Since you’ll be choosing different tests to do with the class, you may need to alter the way in which the results are recorded.

Safety:

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Caffeine allergy is a recognised medical occurrence. Students should be consulted. If any suffer from this condition or would rather not take caffeine they can be part of the control group. Drinking should not happen in the lab. It would be better if this was done in a classroom. The cups should be clean and students should be told that they will be drinking cola. Normal laboratory safety procedures apply.

Adaptations and other ideas:

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  • For those of you wanting to make a “shaky hand tester” (MadLab’s Wonky Wire activity) to study the steadiness of hand, see: http://www.madlab.org/kits/wonky.html (this would add a dash of physics and electronics to the lesson!)
  • BBC News story: Coffee Makes You Forgetful: http://news.bbc.co.uk/2/hi/health/3909085.stm
  • Caffeine is a diuretic, so students may want to go to the toilet more. Fancy recording how many toilet breaks are requested?
  • Reaction test partnered up with general knowledge: try a “Who Wants To Be A Millionaire”-type “Fastest Finger First” quiz (best done with interactive keypads, or an ICT lab).
  • Force meters can be used to test your muscle strength (weakens with caffeine ingestion).
  • Caffeine also causes bronchodilation. Try using a handheld peak flow meter (used for asthmatics, these are cheap and available from chemists) to get an indication of airways’ resistance.

ICT:

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Online reaction or memory tests, looking at websites for information on the placebo effect, other research, using spreadsheets to calculate values and order data.

Keywords: Placebo effect, double-blind trial, ethics, heart rate, pulse rate, caffeine, research.

Citizenship:

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Work-related learning, learning to work in teams, making informed choices and interacting with the media, significance of the media in society, being informed about the world of medical research.

Assessment opportunities:

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To plan investigating correctly identifying variables, collect and record results accurately, testing a hypothesis and taking other factors into account, analyse data to find patterns, planning skills, recording observations, measuring, ICT skills (optional), graph drawing skills and making conclusions.

Curriculum links:

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Considering anomalies in observations or measurements and trying to explain them; the ways in which diet, exercise, smoking and drugs affect health (consistent with PSHE programme); does evidence match the predictions? What effects do drugs have on how the body works physically and mentally?

Lesson 1

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Starter activity:

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Introduction to caffeine (see background notes sheet). Show the video taken through a microscope of a daphnia flea. Get the students to count the heart beat of the flea before and after the addition of a small amount of caffeine. Students should note that the heart beat increases. Students could discuss the reasons for this. (8 minutes total).

Core level main activity:

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1. Students then plan how to conduct the same experiment on themselves. Students should consider the independent variable, the dependent variable, the level of accuracy of the readings and a suitable source of caffeine. Planning sheets can be used to save time and students will need help in learning how to measure their pulse. They should also pay particular attention to other external factors that could affect their pulse during the experiment and so affect the results. (10 -15 minutes).

2. Students take their resting heart beat for 15 seconds then multiply by 4. These results are then entered into a spreadsheet (on a computer or on a prepared transparency). Students may have opted for a second reading to ensure that their results were accurate. (3 minutes).

3. Students are asked to drink cola (note safety information). They must not know that half of the cups contain a caffeinated drink and the other half a non-caffeinated drink. Students should note down the number of the cup they drank from. The teacher will reveal the actual nature of the drink at a latter point in the lesson. (5 minutes).

4. While the students are waiting (about 10-15 minutes) for the caffeine to take effect they should consider reliability. How many of the students’ results are needed to increase to be sure that caffeine has an effect? (10 minutes). 5. Then students take their pulse again. Results are then collected on the spreadsheet as before.

6. Reveal to the students that only half students actually had caffeine. Can they work out which students had caffeine from the results? Highlight on the sheet the students who had caffeine. What does that do to the results?

7. Discussion on the fact that students who did not have caffeine still saw a rise in heart rate. Why did this happen? Was it because they believed the teacher?

Plenary:

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Sum up what has been found out, or not found out. What problems might there be when doctors are trying to find out if a drug is effective? Explain the placebo effect.

Alternative way to run the lesson:

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Another option would be to distribute the cups in three batches. Batch A contains a non-caffeinated beverage such as orange juice or lemonade (check the ingredients) and will be used as a control group. Batch B and C should contain decaffeinated and caffeinated cola respectively. Students should be told that both are caffeinated. And they should be made clear from onset that the effects of drinking caffeine include: an increased pulse/heart rate, faster reaction times, improved alertness, reduced memory and shakier hands!

Explain to the students that they will be testing the effects of caffeine on reaction speeds, the method for testing reflexes and demonstrate. There are two main methods, using an online reaction speed test or catching a dropped metre rule (see the attached worksheet or the online instructions for details of each experiment). Students can at this point make a hypothesis and practice the experiment until 10- 15 minutes have passed since drinking. Try to encourage students to consider why it is important to wait for this period.

When students have experimented to test their reaction times and repeated this several times, each group should get together and record all of their times. These can then be put either into a spreadsheet or onto a whiteboard for the class to consider. Once all results are on the board it can be revealed that Group B had a decaffeinated cola and C had a caffeinated cola. Highlight that an increase in reactions due to the belief that you have taken a stimulant is because of the ‘Placebo Effect’. A placebo effect occurs when something which cannot have any effect, does in fact have the same or similar effect as the drug or experiment being tested. This is usually due to the person being tested believing that they are receiving a drug.

Discuss the differences between results. Hopefully Group A will have slightly longer reaction times compared to Groups B and C. Ask why there is any difference at all between Groups A and B as neither took caffeine.

Homework tasks:

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  • To research the placebo effect.
  • Practise measuring other people’s pulses.
  • Do you believe in the effects of homeopathy/herbal medicine? Why?
  • Create your own advert for an imaginary product which has amazing health benefits? Do you think you could successfully market it?

Lesson 2

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Starter activity:

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Look at results on sugar pills killing pain and the curious effect of the placebo operation (sham operations). Students may have found other examples of data showing the placebo effect from their homework. (5 to 10 minutes).

Core level main activity:

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1. Students are given a table of the results that they collected last lesson. They have been collected into caffeinated and decaffeinated cola drinkers. The difference between the before and after pulse rates (or reaction times). Students can as a class or in groups discuss where there is sufficient evidence here to see the placebo effect. Students should then summarise their findings in a conclusion and explain their findings with scientific theory. (10 minutes).

2. Then students could evaluate the effectiveness of the method that they used. Was it right that they were tricked into believing that they were drinking caffeinated cola? Was there a control in their experiment? How could they add a control (if one wasn’t used) - class discussion? (10 minutes).

3. Planning of the experiment conducted on another class. With their new found knowledge they are now in a position to conduct the experiment with one or even two classes. The class could be split into two groups and conduct the experiment on two other classes. They will need to set out a common method. It is suggested that they split the subjects into three categories, caffeinated, decaffeinated and water (the suggested control group). The students will have to mock up the double-blind model so that the person pouring the cola is separated from the person serving the cola. The teacher could discuss the subliminal signals the server could give if they knew what was in the drink. It is also a useful exercise to get the students to write a consent form (a sample is provided) so the subjects will allow the results to be used and published (well, presented in the classroom!). It is advisable to split the large research group up in the following roles (20 minutes):

a. The research leader: to coordinate the team and present results.
b. The explainers: two students will prepare a statement which they will read to the class being experimented upon. This will invite the students to take part in the experiment, inform them of the theory that is being investigated and explain what will happen to them. They will have to make sure that not too much information is given away.
c. Researcher to organise the subjects in the “waiting room” ensuring that there is calm so heart beats are not raised.
d. Administration staff to collect permission signatures and interview students as to what they had consumed earlier.
e. Pulse readers: they may want to prepare for this at home or if available pulse meters could be used.
f. Cola server: to note down the number of the cup given to the student and to guard the cola.
g. Cola pourer: this student needs to be isolated in the corner of the room.

4. In this lesson the students will only plan the operation and organise the logistics, they will present their plan and employee list at the end of the lesson. (5 minutes).

For those who may need a hand, it may be useful to provide details of what a double-blind trial entails: Sometimes doctors and scientists don’t know which way is best to treat patients, so comparisons are made between treatments. Patients are put into groups and each group is given a different treatment and the results are compared. To make sure the groups start off the same, each one is put into a group randomly. So this is known as a randomised trial. In a blind trial, the patient won’t know which treatment group they’re in. In a double-blind trial, the patients and the doctors don’t know which group the patients are in (but if they need to know, they have a way of finding out!) The reason for such testing is to prevent any bias in scientific research.

Plenary:

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Bring the lesson together by discussing the students’ expectations for the next lesson. It will be useful to discuss professionalism and ethics and perhaps discuss a set of rules which they will all keep to until the next lesson.

Lesson 3

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Starter activity:

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Put up a list of experiments and students are asked to identify which ones might suffer from the placebo effect. (Or perhaps a video clip on the topic, video introduction perhaps from a doctor talking about the placebo effect with their patients and the effect they can have - 2 minutes).

Core level main activity:

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1. Review the plans created last lesson. (5 minutes).

2. Students get “into role” – as devised in previous lesson (5 minutes).

3. Organise classroom furniture to allow a conveyor belt of activities, i.e. read information sheet, sign consent form, have pulse taken, drink cola, wait, have pulse taken again. (5 minutes).

4. Conduct experiment (40 minutes). Students also collect results together on a shared spreadsheet or collect them all and hand in to the teacher.

5. Review class discussion on the experiment. What were their successes, what went well?

Depending on time constraints, this next part could be done in a following lesson:

1. Students are given a table of the results that they collected last lesson. It should be possible to compare the results collected by the two groups. Which results are reliable, are there any differences? What should they do to the results to see if the placebo effect happened? (15 minutes).

2. Students can then analyse the results and present them in the form of a graph (15 minutes).

3. Students are to draw general conclusions to the experiment as a whole. (15 minutes).

Plenary:

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How has this lesson influenced how they view taking medical drugs and receiving advice from their doctor?

Extension:

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Discuss how powerful the placebo effect is. Certain drugs claim to “buzz you up” so that you can concentrate better, whereas others claim to “calm you down” so that you can concentrate better? Is this possible? But with the placebo effect in place, who knows…

And for those of you interested in sports science:

Caffeine was never banned in training, but was controlled in competition, and the urine concentration had to be below 12 ng/ml. The World Anti-Doping Agency (WADA; http://www.ada-ama.org/en/) sets the list of banned substances in sport, and caffeine was removed from the list in 2004, but is now on the monitoring list i.e. they look at the concentrations, but take no action. So not to worry if you have a cup of coffee on your way to the gym, then!

The Placebo Effect: Feedback from teachers who trialled and designed the experiment

The placebo experiment was trialled with a top set Year 8 class. The majority of them (all but two) had heard of the term “placebo effect” but only a few of them knew what it meant and could describe it accurately. One student understood the concept of a double-blind trial.

It would be better to say less at the start, and have more of a discussion around the results. In the first trial of the experiment, I found that I did too much talking, and the students tried to force the effect onto the results.

We collected a vast range of results in the first trial of the experiment. A great deal of the discussion afterwards was on the statistical significance of the results, which would have to be handled carefully with most Year 8 classes.

The same class conducted the experiment on two other Year 8 classes, having planned the experiment themselves. They also measured the pulse rate of the other students. This caused more discussions as they questioned the accuracy of each others’ methods of taking accurate pulse readings. We mimicked a true clinical trial process by even getting students to give their written consent. Students particularly enjoyed this part of the lesson and paid particular attention the logistics of the activity.

These activities came at the end of an extensive investigation on the effect of caffeine and aspirin on daphnia heart beats under a microscope. The students were fully aware that caffeine did speed up the effect of the heart beat.

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