Activity #1

The following three posts discuss ways of showing students the effects of expectation on perception. Joe Hatcher uses backwards-language tapes to do this and refers to the backwards-language experiments of John Vokey and Don Read at the University of Lethbridge. Tim Gaines describes a convenient method of creating your own tapes. Gary Peterson has found that even blank tapes provide an effective demonstration of expectancy effects.

Wed, 3 May 2000
Joe Hatcher
Ripon College
hatcherj@mail.ripon.edu

One thing that I try to do in my class is to reduce the "certainty" factor that often stops critical thinking. I'd like to tell you one of the exercises I use to do this, and ask for your suggestions and experience.

I use the "backwards language" tape of Vokey and Read, and do it in the following way. I first play the first few selections of the tape to get them in the mood, and they play the crucial last section. I ask if anybody hears anything; the answer is always no, or some small phrase is reported. I then ask them how certain they are, on a 1-5 scale, that there is nothing intelligible in the section they just heard, and play it again for them before they rate; I usually get all 4s and 5s. I then select about four people from the audience, tell them the phrase to listen for ("snatched her nips"; Vokey and Read suggest that "scrapped her ships" works just as well, but alas, it doesn't for me). I then play the selection again; the looks on the faces of the four selected people are rather priceless. THEY hear the selection perfectly clearly, and no one else does. I then ask them how certain THEY are that there is something intelligible on the tape, and they all give fives.

Finally, I tell the entire class what to listen for, and play the tape again. Of course, this time everybody hears it. We then discuss the experience, always touching on the idea that, if one were simply told what to expect from the beginning, there would be no "doubt" that the offending phrase actually existed on the tape. I also suggest an application of the same concept to person perception, in that if we have been told what someone is like, perhaps we see that with certainty as well.

Thu, 4 May 2000
Tim Gaines
Presbyterian College
mtgaines@cs1.presby.edu

You may be interested in another way of recording something backward. Many computers these days come with a sound card and software that will permit digital recording from any input (microphone, CD, tape, etc.). You can then graphically display the waveform and edit it in interesting ways. I have used this for some labs in speech perception. One feature that is available on the SoundBlaster card and probably others is the "reverse waveform" function. Interesting effects! It is easy to record onto a cassette directly from the computer. There is a limit to the length of the digital files that can be set up and it probably depends on the amount of RAM available.

Wed, 3 May 2000
Gerald (Gary) L. Peterson
Saginaw Valley State University
peterson@svsu.edu

In my community skeptics group, one of the members showed us how to reverse a cassette tape (not an easy chore) and then we played the tape and enjoyed hearing all sorts of things. First, someone would say, "hey I heard XXXX, then we all listened for it, and most heard what was suggested---well, we tried hard ha. I have a copy of his article on how to do this, and could snail mail it---but again, it is not easyƒ. Anyway, the point here is you might just try playing a blank tape, or have static on it and try the same thing that Joe did with the Vokey and Read tape. My colleague has also tried to find ghosts on photos that are just dark prints. I think we could do a visual demo on this too.

Wed, 26 July 2004
Stu Tanquist
Stu@tanquist.com

Activity #1 offers a great activity suggestion, but notes that reversing
speech can be a challenge. I found a simple solution.

http://www.talkbackwards.com/ has a free online utility where you can upload a .WAV file and it will immediately reverse the speech and play it back. It plays the file and creates a link titled, "Your reversed file." If you right-click on the link and select "Save Target As" from the pop-up menu (Windows users), you can save the reversed .WAV file to your hard drive. The site works quite well. In fact you can resubmit your reversed file to create a good rendition of the original file.

To find sample .WAV files, go to http://www.altavista.com/, click the
"MP3/Audio" tab, check only the "WAV" box, and enter a keyword in the search box.