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For their skills class, students have been learning that in the real world, you often need to connect multiple disciplines to solve problems, which culminates in a CSI unit trying to figure out who stole an item. In Psychology, the students learn about physical responses around lying. In Physical Computing, they have been learning about sensors and breadboarding. For this lesson, students will create a lie detector, which works by showing on a computer screen what the voltage differences are in pulse and galvanic skin sensors.
Current image from: https://thomaskosch.com/index.php/2017/12/17/galvanic-skin-response-powered-by-arduino/ – to be replaced by an image of me on Monday.
Students will understand
Students will be able to:
This lesson came up entirely naturally – I learned that there was going to be a transdisciplinary CSI lesson that last year Jaymes Dec had built a lie detector for, and this year I realized my students could very easily do the same – I was moving into using pins and breadboards, and helping students pull back layers of how things worked, and the galvanic skin sensor response is a super easy way to bring home the idea that sensors are often just sensing changes in resistance. So, we’re connecting student learning across disciplines, opening up an understanding of what is going on in computing devices in the real world. Students were excited to learn about this, and talk about it, especially given they had done the same project before. When I spoke to my students, they were also naturally interested in the ethics of making lie detectors and if we should trust them, bringing in Philosophy as well.
Ask students what they know about the physical signs that someone might be lying
From Psychology class, students should be able to answer this question – they should know that someone might sweat more, and their heart might race faster, or they might be less able to answer complex questions if they are lying. Write these answers on the board so students can see them while they answer the next question.
This question can be done as a think/pair/share
Connect what students just said about lying to what they know about resistance and electronics
Ask students:
It will probably be harder to just come to the conclusion that you can change light levels bouncing back for the pulse sensor, so you can just explain that to students.
You may have prepared small containers with enough materials for a group of students to create their lie detectors. Pass those out to each group of students making a lie detector and make sure the students understand the materials.
Students build the galvanic skin sensor using the materials you have provided
If students have understood the lessons on how you can connect a microcontroller’s pins to a breadboard and a circuit, they should be able to connect jumper cables correctly to read values, so you should not necessarily provide students with the instructions; you should instead wander and help them as necessary.
Here are the steps for the galvanic skin sensor:
Wire up the pulse sensor as described here: https://pulsesensor.com/pages/micro-bit-fun
Program the sensor to collect readings
Students should also know how to do this – wander and help as necessary.
Wire up the pulse sensor as described here: https://pulsesensor.com/pages/micro-bit-fun
Look at the data - what can you tell from it?
Have someone play 2 truths and a lie while hooked up to the pulse sensor and the Galvanic Skin response sensor.
How do you feel about using GSR and pulse data to detect lies? Why does it work? When doesn't it? Would you be comfortable using it in a court of law? Who does this disproportionately affect?
Have the students discuss these questions in small and large groups to connect the lesson back to psychology and ethics and the overall project.
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