Reach Out and Touch Someone

Transcription

1 Reach Out and Touch Someone Understanding how haptic feedback can improve interactions with the world. The word haptic means of or relating to touch. Haptic feedback involves the use of touch to relay information, and is often used in conjunction with sight in computer controllers. While haptic feedback is often just a buzzing or vibration, new trends have created devices that can mimic other aspects of touch. This lesson introduces how haptic feedback improves sensory understanding of the world and how haptic feedback can create the illusion of an interaction that doesn t actually exist. Next Generation Science Standards (NGSS) Disciplinary Core Ideas LS1.D Information Processing. Each sense receptor responds to different inputs, transmitting them as signals that travel along nerve cells to the brain. The signals are then processed in the brain, resulting in immediate behavior or memories. Science and Engineering Practices 1. Developing and using models. 2. Constructing explanations (for science) and designing solutions (for engineering) 1

2 3. Engaging in argument from evidence Engagement: The engagement portion of a lesson brings students into a topic by providing a situation that promotes curiosity. In addition, it connects the new lesson with material that has been previously studied or is already known by the student. Human senses can be quite acute, but they also have limitations. Finding those limitations can help us to avoid being fooled. Some of the time, however, we can exploit these limitations to create illusions that allow us to have sensations that can convey information even when the actual situation doesn t exist. Activity 1: Mass Illusion Humans have a surprisingly difficult time comparing the masses of objects. This activity shows that our sense of touch is mediated, at least in part, by vision. Students can see how we can create false impression of the weight of something by careful manipulation of its shape and size. Materials (Per group) Expanded polystyrene (Styrofoam ) block measuring 19 cm x 19 cm x 19 cm (see below) 250 gram mass from a weight set (preferably metal) Hacksaw or hot wire cutter Scale Paper clip String 2 two-liter and/or 2 one-gallon bottles of water Plastic or cloth grocery bag with a handle Blindfold 1. The teacher should build the blocks ahead of time. Craft stores usually have blocks of Styrofoam this large, but you can also build them up with Styrofoam safe glue. Hacksaws cut Styrofoam just fine, though a hot wire cutter will leave a smoother edge. 2

3 2. Have students hold first the expanded polystyrene block in their hand and then the mass from the weight set. 3. Have them determine individually and in writing which one feels heavier or if they feel like they are the same mass. Most students will determine that the metal mass feels heavier than the Styrofoam block, although some students will guess that the two objects weigh the same, assuming that there is some sort of trick. That s fine. 4. Weigh the block and the mass. If you were careful about cutting them, the expanded polystyrene block should weight about 275 grams, almost 25 grams heavier than the weight. The Styrofoam comes in different densities but it typically has a density of about 0.0 g per cubic centimeter. Since the block is about 6850 cubic centimeters, it should mass about 275 g, compared to the 250 gram mass. If your weight set comes in different divisions (like a mass that is 200 g rather than 250 g), just cut the Styrofoam so that has about 10% more mass. 5. For most people the illusion doesn t go away after knowing the true masses, just like optical illusions often don t go away after being explained. 6. The illusion s cause isn t fully understood, but students can make progress in trying to sort out what is going on. Ask students to see if the illusion is as strong if they hold both objects at the same time, one in one hand and the other in the other hand. Most students find the illusion is less strong in this situation. Have students close their eyes (or wear a blindfold) while feeling the weights. Again most students find the illusion becomes weaker. 7. Attach strings to the polystyrene block and metal weight. Have students try to measure the weights by only holding the strings. Most students find that the illusion is less strong in this situation. If students close their eyes (or wear a blindfold) and hold the dangling objects only by the string, the illusion seems to go away completely. 8. Ask students to make suggestions about the cause of the illusion. Typical answers include that we are basing out idea of heavy not on mass but on density. The Styrofoam block is less dense than the weight. Other responses incorporate the idea of pressure. The metal weight applies a higher pressure to the hand since it is smaller. When holding a string the sizes of the objects are equalized. 9. Ask students to imagine how this illusion can be used in a different situation to make a heavier object feel lighter or a lighter object feel heavier. 10. Ask students why visual information could be helpful to an organism in assessing the mass of an object. 11. Students should ask if they think the shape matters in their perception of mass. Have one student close his or her eyes (or wear a blindfold). The two water bottles should 3

4 contain slightly different amounts of water. The lighter of the two should be placed in the bag. Ask the student to determine which is heavier the water bottle held directly in their hand or the water bottle in the bag. 12. Ask students to begin constructing a model of how this particular feedback system might work. This will be their first draft. Because there are at least two inputs, the tactile feedback (pressure) and visual feedback, students should first propose how each input works independently of the other (visually, a large or metal object may look heavier, for example) and how the dual inputs may be processed together to produce one feeling about the mass. Exploration Exploration is where students use prior knowledge to investigate ideas through activities to facilitate conceptual change. Activity 2: Fake It Till You Make It How heavy an object feels is related to how hard gravity pulls down on the object, but gravity isn t the only thing that can pull an object down. In Activity 1 we discovered one way to make objects feel different than their true weight, in this activity we examine another. We usually believe that how hard it is to lift an object is a good measure of its weight since most of the time we are lifting only against the downward force of gravity. However, if additional upwards or downwards forces exist, objects can be made to feel lighter or heavier than they really are. Materials Small dumbbells of different sizes ( about 1, 2, and 3 kg) or two-liter bottles filled with water with hooks attached to the top and bottom Hooks Rope Closed-toe shoes Blindfold 1. Have students hold onto one end of the dumbbell or bottle. 4

5 2. Have them lift the dumbbell up and down getting a sense for the weight. Hook another dumbbell to the bottom. Have the students get a sense of the weight again. 3. Have the students return to having one dumbbell in their hands. Have them close their eyes (or wear a blindfold). Ask them if they can tell the difference between having another dumbbell added to the first or a classmate pulling downward on the dumbbell. 4. Students will find it a challenge to mimic the behavior of an additional mass, but after a while most can get to the point where the holder can t guess correctly all the time. 5. The mimicry is possible because, while weights pull down from the force of gravity, other forces can still seem like gravity s force. 6. Students who held the weights should elaborate on the different aspects of the masses only versus the mass plus classmates pulling downward experiments made it possible to distinguish between the two experiments. The students doing the pulling should elaborate on how they perfected their technique to ultimately trick the blindfolded classmate into believing it was another mass. The descriptions of these students should be used to refine the model they started building in Activity 1. Activity 3: Walking on Pillows Shoes are sometimes described as being so comfortable as to be walking on pillows. Would that really be a good thing? This activity demonstrates how important haptic feedback is. Without a good sense of touch between feet and the ground, it is harder to walk. Materials 2 pieces thick foam rubber cut a couple inches larger than a foot or old small but thick pillows 2 wooden blocks approximately the same thickness as the pillow or foam rubber tap 2 bicycle helmets 1. Explain that the students are going to strap foam to their feet. Have them predict how walking will be different with the foam. Try to get them to be specific. Ask them to be specific about how feeling the floor might be different. Typical prediction revolve around the fact that the floor will be softer. Most students will say that it won t be more difficult to walk on the floor. 2. Have a student wear a bicycle helmet. The risk of falling is quite low, but better safe than sorry. Have the student tape the pillow or foam rubber to their feet. 5

6 Have the student get used to the weight, and then have the student walk around with other students for stability. Notice the student s gait. 3. Have a different student wear the wooden blocks and a bicycle helmet. Have other students spot the student as he or she walks around the room. Note the student s gait. 4. The two students swap footwear. 5. Afterward, they should describe how walking on the foam rubber was so difficult. Part of the reason is that the foam rubber is more unsteady since it compresses unevenly. (This can be normalized with the block some by rounding the block so that it is also unsteady.) With more pressing, though, the students involved in the experiment will often explain that the foam rubber seems strange because it is difficult to tell when your foot has compressed the block completely. Students will often say that they cannot tell when their feet are touching the ground. 6. The trouble seems to come from the lack of feedback. When walking normally, people can feel the pressure of the floor pressing back on their feet. It is a feeling of solidity, and foam rubber, however, interferes with this sensation by having the feeling come on gradually and continuously, making it difficult to decide when to switch weight from one foot to another. This loss of haptic feedback makes walking difficult. 7. The phenomenon is similar to having your foot fall asleep, a situation when the normal sensation from the foot is reduced or eliminated. While the pins and needles feeling is often uncomfortable, walking is difficult because of the lack of feedback. It is often hard to tell when your foot is touching the floor. Activity 4: Hot and Cold Do the sensors in your skin detect absolute or relative temperature? This simple activity demonstrates how sensations can be relative to the experience immediately preceding that sensation. Materials: Blindfold Large bowl of ice water Large bowl of room-temperature water Large bowl of hot water (about 120 degrees F) 6

7 1. Ask students if they think that their temperature perception is stable (unchanging). Common answers are yes, although some students will recall a time when they stepped into a hot bath or shower with very cold feet and thought they would get burned. 2. There are many variations on this demonstration so teacher should feel free to experiment. The student first dips one hand in cold water and one hand in hot water and is asked how they feel. Cold and Hot is a likely answer. The student is then blindfolded and then dips both hands in ice water for seconds. The student will likely need guidance from another student to know where to dip his or her hands. Immediately afterward, the student should dip one hand in hot water and the other in room temperature water. Ask the student how each hand feels. Typically, the room temperature water feels warm and the hot water feels scalding! 3. Once the student recovers from the experience (dipping both hands in room temperature water helps), the student then dips their hands in the hot water for seconds. Immediately afterward, the student should then dip their hands in roomtemperature water and the other hand in ice water. Ask the student how his or her hands feel. The ice water often makes the students hands tingle or feel hot. 4. Students are asked to add this additional observation into their developing model. Note: The blindfold is not necessary for this demonstration but helps the students focus on the sensory information in his or her skin. If another student is not available to guide the sensing student s hands, then a blindfold should not be used. Explanation This is where students put together their ideas to create a mental model of how a system works. 1. Ask students to make a final model to explain and define haptic feedback. The model should include enough detail to explain what information haptic feedback provides to an organism that is different from visual or auditory feedback. 2. Ask students to give an example of a situation where haptic feedback is common. 7

8 3. Ask students to apply their model of haptic feedback to their example. Does the model fully explain their example? If not, how can the model be improved? What date or information are lacking? What experiment could fill in the gap in the model or fix a problem with the model? Elaboration In this section students use their ideas and extend it to a novel situation. Students are asked to imagine a situation where they don t have haptic feedback and it would be useful. An example is driving. Early steering wheels had a mechanical connection from the road to the steering wheel which relayed road conditions to the hands of the driver. Things like bumps in the road jostled the driver s roads, and curbs would prevent the wheel from turning. Improvements in power steering however, removed these connections, making the wheel seem disconnected from road conditions. Many people found that disconnecting, making the wheel seem disconnected from road conditions. Many people found that disconcerting, and most modern steering mechanisms mimic the feel of older steering devices to provide haptic feedback. Students who knowhow to drive can explain the situation of feeling the road through the car. Evaluation Teachers and students determine if they understand the material. The teacher will ask the students to describe a system that they use every day that would be nearly impossible to use if it provided no haptic feedback. For example, in writing and drawing, a person feels the paper and pen or pencil point pressing aback against their hand. Students are asked to demonstrate a system that doesn t have haptic feedback and explain how difficult it would be to use. Students then try to think of ways to return haptic feedback to the system. Patents Patents are a way for inventors to create property rights in their inventions. Patents provide inventors the right to exclude others from making, using, offering for sale, or selling the invention in the United States or importing the invention into the United States. Please see What are Patents, Trademarks, Service Marks, and Copyrights? 8

9 In exchange for this right, inventors have to disclose to the public how to make and use the inventions in their patent application. This information often can help other inventors make improvements, as well as spur on new inventions. Reading a patent introduces students to technical language and gives them familiarity with the way inventors describe their work. The language can sometimes be difficult for students; however, it can also be instructive to see what claims the inventor has made, and to learn more about how the device or process works. Drawings can also be helpful in understanding some of the key design elements of an invention. Please look at The Anatomy of a U.S. Utility Patent and then at the following two patents related to haptic feedback. US Class 700/264 (Data Processing: Generic Control Systems or Specific Applications) AU 3664 US Class 345/173 (computer Graphics Processing and Selective Visual Display Systems) AU