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Tim Bell,
Department of Computer Science, University of Canterbury,
Christchurch, New Zealand
tim@cosc.canterbury.ac.nz
Science shows are commonly presented for the general public, and especially children, at science centers and festivals. Usually they use attention-grabbing experiments from the physical sciences, and the science of computing is absent from such presentations. This paper describes a series of demonstrations that present fundamental ideas from Computer Science in a manner that will be engaging to a general audience. The show has been presented to school classes, at science festivals, and as a children's event. The results from questionnaires distributed at the shows indicate a favourable reaction from the public.
Public understanding of science (PUS) is becoming important for several reasons:
Most major cities have at least one Science Center, annual science festivals are common, and travelling science road-shows visit schools and small towns.
However, shows at these venues tend to focus on the physical sciences, which lend themselves to spectacular demonstrations such as hammering in a nail with a frozen banana or exploding custard powder dust. In such an environment computers generally make a poor showing -- there might be a rather over-used computer sitting in a corner running a CD-ROM or providing Internet access. A generation of children accustomed to using Nintendo machines are not likely to be impressed, and members of the public who have had only bad experiences with technology are not likely to be interested either.
Furthermore, using the Internet or a CD-ROM program is hardly computer science -- a subject that is full of wonderful ideas including elegant data structures, clever algorithms, and apparently intractable problems. The general public often confuse Computer Science with computing or computer technology.
This paper describes ways to present some of the great ideas from Computer Science to a general audience. These demonstrations are suitable for children as young as five-years old but also for adult audiences. They are particularly suitable for larger audiences (see Figure 1), such as a classroom of school children, or even an auditorium of several hundred people. The demonstrations described below have been used for shows at two International Science Festivals (Edinburgh and Dunedin, 1998), and have been developed further for use at a local children's festival (Kidsfest, Christchurch, New Zealand, 1998). They have also been presented in schools, to as many as several hundred children at a time.
In the following section we present a brief discussion of the philosophy behind the design of the show. Section 3 describes the demonstrations we used for a one-hour show (although a few could be selected for a short 5 or 10 minute demonstration). Section 4 discusses general principles for packaging the demonstrations, such as the use of audience involvement. In Section 5 we analyse the results of an exit survey on several of the audiences, particularly with regard to attitude changes.
One of the important principles in the demonstrations described in this section is that they generally do not use a computer, but instead use large-scale props such as cards and masking tape. This avoids the obsolescence that is inevitable if the presenter relies on technology to capture attention. Also, there is a growing suspicion of technology. Frustrated users wonder whether "productivity tools" really make them more productive [5], educators are querying moves to fund computers in schools at the expense of other programs [6], while others point out that computers fall far short of what the marketing promises [7].
One way to do computing without a computer is to have the audience simulate a computer (e.g. [1]), which gives insight into how the computer works, but can easily become a "busy" activity where the participants lose sight of the big picture. Other ways that Computer Science departments have involved the public is to run programming competitions (e.g. [2]), although this mainly attracts the attention of people already very interested in the technical side of computing. An alternative that has been proposed is the "Computer Science Fair" [4], although this still focuses on the technical side of using computers, rather than the ideas behind Computer Science.
Our approach is to use "unplugged" demonstrations, which are participatory activities in which ideas from Computer Science are used as challenges and puzzles for the audience. These are more likely to appeal to the audience's curiosity, and interest can be increased by making an activity competitive, or even better, turning it into cooperative problem solving. Many of the demonstrations have been developed from a collection of smaller scale activities [3].
To do this trick with a large audience, a volunteer is given 25 magnetic cards, and asked to place them in a five by five square on a board. Our cards were white on one side and black on the other (they can be made by sticking refrigerator magnets back to back). While the volunteer is putting the cards up, there is time to talk about how computers work with only zeroes and ones. Ask the audience what kind of digit has only two values (a binary digit), and what the short name for it is (bit).
Now add an extra row and column to the volunteer's "bits," using the pretence that you are making the problem even harder. In fact, you are adding parity bits -- an extra bit in each row that makes the number of one bits (white cards) an even number.
You look away while the volunteer flips over one of the bits, and then (with appropriate drama) you look carefully at the 36 bits, and identify which one was flipped (its row and column will have an odd number of white cards).
In our show, we then asked the audience if they wanted to know how to do it (a safe question), but said that we would tell them at the end.
Explain that each volunteer's card is either visible or not (each is a bit). Now challenge the volunteers to flip their cards over so that exactly five dots are showing (depending on how competent the volunteers are, this may invoke help from the audience).
Once they have the idea, there are many activities that can be done with these cards. Displaying the numbers 1, 2, 3, 4, ...is instructional; for example, they may observe that each card flips half as often as the previous one. The audience can figure out the largest number that can be represented, the smallest one (zero, not one), and try to find two representations for the same number.
Then experiment with giving them numbers using zeros and ones (i.e. decoding a conventional binary number), mapping the five-bit numbers onto the 26 letters, and representing bits using high and low beeps (discuss modems). Once this has been covered, it is possible for the demonstrator to "sing" a short "e-mail" message using high and low beeps (the message "HI" is easy to send).
You can also point out that the five bits can be represented by the five fingers on your hand (each finger is up or down), so you can count to 31 on one hand (but watch out for some of the gestures!) Using two hands you can count to 1024, and if you take your shoes off, to more than a million.
The image is coded using run-length coding of alternating black and white pixels. For example, the sequence 3, 4, 5, 1 represents 3 white pixels, then 4 black pixels, 5 white, and 1 black. Some coded images are given in Activity 2 in [3].
We found it helpful to have most of the image already displayed, so only the last few lines needed to be done with the audience. The people furthest away from the front will probably see the image most clearly; suggest squinting for those who can't make out the image.
You can then point out that the audience now understands how fax machines work -- they know how to code numbers using beeps, and how to represent images using the numbers. It's just that fax machines are faster (get the audience to try making thousands of beeps per second), and they use smaller ink cartridges.
We began with a demonstration of the Stroop effect [8]. We used about six cards, each of which had the name of a color on it (blue, green, etc.), but the name was printed in a different color (e.g. blue was printed using red ink). The cards are held up one at a time for the audience, who must call out what the color of the writing is. Most people stumble doing this as they automatically read the word rather than the color. Make sure that the word is very clear, and that you don't obscure it with your hand.
We then got a volunteer from the audience (an adult or teacher is best), and gave them a card with a list of such colors on it. The audience enjoys watching them hesitate as they try to read it as fast as they can. Ironically, younger children who can't read can do better at the task -- another trick is to hold the list upside down.
We then asked the audience who had used the Windows operating system, and what is shown on the button to stop the computer (it is "Start"). We pointed out other confusing contradictions in HCI, such as "Yes/No/Cancel" options, or "Hit any key" when there isn't an "any" key (and even if you know what it means, the shift key doesn't work.) We further illustrated the need for people-oriented programmers by displaying a series of amusing error messages from real systems, such as "Keyboard missing; press F1 to continue."
We then got the people with cards to sort themselves into order (this is an interesting exercise in itself), giving new cards to people who had already revealed their number. This time a new volunteer was given the five candies, and encouraged to use a binary search. As each card was shown, we got the eliminated people to sit down, which showed dramatically the power of this divide and conquer strategy.
We also illustrated divide and conquer by feeding the entire audience with one candy bar; the first person gets half, the next a quarter, and so on (a sharp knife is required!) The people at the back might be worried, but we pointed out that we can always keep passing the candy bar around so they can always have more -- this is a humorous way of conveying the idea that the sum of an infinite series can be very finite!
The technique used to maintain privacy is that the first person writes down a random four-digit number on a pad. They add their age to it and write this on the next sheet, keeping the first sheet and passing the pad onto the next person. Each person in turn adds their age to the number on the pad, tearing off the top sheet. At the end, the first person subtracts the initial random number, and calculates the average. While the process is going on there is an opportunity to discuss applications of cryptographic systems. If it takes too long, let the adding continue while you start the next activity.
Packaging a demonstration in a way that attracts and engages an audience is essential if the show is to be successful. For a public show, the emphasis is more on entertainment and provoking curiosity than conveying information, which may not sit easily with people from a traditional educational background.
The first problem is attracting an audience. Titles that include the word "computer" may discourage technophobes who would have benefited from the experience. The challenge is to present the advertising in a way that conveys the excitement of the show, and that the show is suitable for a general audience. Scientists are often tempted to construct dry descriptions, whereas the public are looking for entertainment, humor and mystery.
The following extract from our advertising dresses up standard Computer Science topics (error detection, data compression, binary search, and cryptography) in a way that is intended to provoke curiosity.
This wacky show takes kids (and the young at heart) through some of the great ideas in Computer Science, using low-tech games, magic tricks, and stories. Come and see the giant fax machine, find out how to feed a crowd and always have food left over, and learn new ways to keep information secret.
A key element to attracting an audience is the title or the reputation of the speaker. You may not be able to do much about the latter, but judging by attendances at science festivals, a title can make a big difference. The titles of shows that attract the most interest from children tend to mention food (such as custard) and excitement (such as explosions). Fortunately the material presented in the show described above has both of these ingredients, giving plenty of opportunity for creative names for a show.
The descriptions in Section 3 have hinted at how the show should be run. Notice that the topics are not usually covered in a lot of depth; too much detail can go over the heads of such a mixed audience. The main goal is to provoke curiosity. Key ingredients are: audience participation ("I need a volunteer"), humor, suspense ("Do you think she will find it?"), enthusiasm ("Give a big clap for the volunteers") and provoking curiosity ("Do you want to know how I did it?"). It is much more effective to ask the audience for the answers ("How did that work?", "What number will be next?") rather than just tell them the answers. This distinguishes the show from a lecture, and reinforces that the ideas don't come on stone tablets, but that ordinary people can think them up if they apply themselves to the problem.
With a little imagination, most topics can be made interesting. For example, the topic of statistics does not always generate a lot of interest, but playing lotto does. To make a dull topic interesting, the presenter needs to relate it to things that affect people's lives, such as computers that frustrate or threaten them, or turn a technical problem into a challenging or competitive game.
A large scale show will inevitably have hitches, such as volunteers not following directions, or props getting damaged or lost. These can generally be dealt with positively and with humor. For example, in one show the volunteer for the parity trick flipped more than one of the parity bits. The audience soon learned that the trick wouldn't work in this case, and the explanation of the trick had to be made straight away to explain what was wrong. In another case, one of the "bits" in the binary number would not keep the card still. This was used to point out the effect of the bit ("The number is seven -- no, five -- no seven ...").
The show is best run by a computer scientist, rather than a non-specialist. Although the depth of knowledge covered in the show may not be great, if the presenter does not have the depth to back up the demonstrations then the show can be unconvincing to an audience, particularly if the demonstrations don't go as expected, or if questions are asked.
We received 212 survey responses. The gender split was reasonably balanced, with 54% males, and 46% females, although 63% of the target age range (6 to 12 years old) were male, while 70% of the adults were female, supporting our perception that there was a tendency for mothers to bring their sons to the sessions. 67% of the respondents were aged from 6 to 12, with 6% under 6, 7% teenagers, and 20% 20 and over.
When asked why they came to the show, 35% gave entertainment as a reason, and 49% ticked "To learn about computers" (multiple reasons were allowed).
The responses to the question "After seeing the show, has your interest in Computer Science increased/decreased" are shown in Figure 4. There is a strong indication of a positive increase for both males and females, although it is slightly stronger for males, and two of the 98 females indicated a strong decrease.
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We also asked how surprised they were by the topics that Computer Science includes. The responses, shown in Figure 5, indicate that most people had changed their view of the subject, again with a stronger response from males.
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The survey included the question "Would you recommend the show to friends?" 56% said "Yes, definitely," 40% said "Yes, perhaps," and 4% said "No." We consider this a very positive response to a show that teaches binary numbers, error correction, and searching algorithms!
The respondents were also asked for general positive and negative comments. The positive comments mentioned all of the activities, particularly the parity trick, binary numbers, searching, and sorting networks. Several respondents enjoyed a parrot puppet that we used during the show (as a pun on "parity"). The negative comments often mentioned missing out on getting a candy. A few mentioned that sitting on the floor was uncomfortable after an hour (seats were available for adults only in some shows), while others said that the show should have been longer.
Several times members of the audience had told us with excitement that they finally understood concepts like the binary number system, and how computers store data.
The shows have demonstrated that it is possible to attract a general audience to a talk about Computer Science, and the surveys indicate that the audience would recommend it to others. A significant increase in interest in Computer Science was indicated by the audience, and the majority expressed surprise at the topics that Computer Science includes.
Such shows can be used to help children distinguish between computing technology and computer science, and make more informed career choices, as well as increase their general knowledge about issues surrounding the design of computer systems.
More information about the show is available from the "Unplugged" web site (+http://unplugged.canterbury.ac.nz+), and a video of the show can be requested from the author.
The author is grateful to Matthew Powell, who assisted with the preparation and running of the shows. The development of the activities has also involved Mike Fellows and Ian Witten, and Sally Jo Cunningham and Jane McKenzie provided helpful comments on the paper.
Modified: 15-Sep-1998
