I think the book and our AP Psychology program so far has been organized in a very logical manner. We studied the history and meaning of psychology the the first chapter, scientific research methods in the second chapter, neurobiology in the third chapter and sensation and perception in the fourth – what we are studying now. The language in which the textbook was written is uniquely interesting. It “talks” to the students while retain a certain degree of formality, similar to my math books. No wonder why these textbooks are expensive.

Having said that, I must also point out a few technical misconceptions I have found within our AP Psychology textbook. However, I do not think any of the writers are to blame because after all, there specialize in psychology not physics and mathematics. Here are the mistakes and their corrections. First, intensity and amplitude are not the same concepts (see page123) . Amplitude – the book defines this correctly – is essentially the height of a wave, or more technically the distance between the point of equilibrium and the local maximum. Intensity – this the books explains wrongly – is the measure of how much energy is in an area, e.g. W/m2. As shown, even though amplitude and intensity can both affect the energy carried by a physical wave, they are by no means synonymous. Further more, that applies to both sound and light waves. In case anyone is interested, the standard unit of sound intensity is measured in decibel or dB, mathematically defined as β = log (I/I0) where I is the intensity of a sound taken into consideration and I0 is the absolute threshold of human hearing. Second, frequency and wavelength are different properties of a wave (see page 127). Frequency is the number of periods a wave possesses in a given interval, mathematically 2π or physically per second as in the definition of Hertz. Wavelength is, as its name may suggest, the how long each cycle is. Mathematically, wavelength is the reciprocal of frequency. Thus, for example, if a wave has frequency 2/2π then its wavelength is π.

I will try to find some time to engineer auditory examples of pitch and loudness in order to remove any confusion I have between the two. Mathematically, pitch and loudness can be deduced rather easily, on the other hand.

I would also like to advise caution to everyone. Simply looking at the graph of a wave to determine its properties can be misleading. Ensure that the scale of the graphs are the same first. The following images should be sufficient to illustrate this point. Although they appear to be the same, they are mathematically different. Hover your cursor over each image to see why.



4 responses »

  1. Mr. M. says:

    Excellent post Scott! Excellent! I suspect that our esteemed authors, Zimbardo et. al, know the difference between amplitude & intensity and wavelength & frequency, though. I most certainly didn’t, and I thank you for educating me! That said, I believe that the difference is not significant for the average introduction to psychology student. Should anyone advance far enough in their study of sensation and perception, though, they would be acquainted with the technical differences.

    I also appreciate your warning and demonstration about comparing graphs. We should all be aware that this is a favorite trick of advertisers to manipulate the impression while being technically honest.

    Mr. M.

    • hoaitramk says:

      Mr.M . Are those information that Scott said it right , i mean the book provide wrong information . I don’t really understand what he is talking about . Will we discuss it con Monday ?

  2. mehappy777 says:

    To be honest, i don’t really understand but it’s a very nice post you have there. I can see the difference and why you keep claiming frequency and wavelength are not compatible to each other now. I am very astonished at the graph, another golden advice from Captain Nerd! LOL

    I agree with your opinion about our AP textbook, it’s lovely and quite casual. It gets informative and formal when it gets into the key points and facts of the chapter. Mr. Zimbardo amazes me!

  3. Kisha Vara says:

    I love your design, it’s nice when you can tell somebody actuallly puts effort into a post, and gives the layouts. If you set up updates value.

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