Talk:Stevens's power law

Initial comment
I figured out that $$\alpha$$ is the exponent in the given table, but what value is k supposed to be? the article doesn't mention k anywhere. --Abdull 11:55, 23 Mar 2005 (UTC)

k depends on the particular type of stimulus and the units used. It doesn't make much sense to specify k since there are no clear units for "subjective sensation" anyway. AxelBoldt 23:35, 10 September 2006 (UTC)

Law's predictions
Naive that I am, I would claim right away that
 * $$\psi(I) = k I ^a $$

is obviously false, at least in cases where a < 1. The law predicts in these cases that, if I is close to zero, tiny increases in I result in tremendous increases in &psi; (the first derivative of &psi; at 0 is infinite). But we all know that when I is close to 0, &psi; is equal to zero. AxelBoldt 23:35, 10 September 2006 (UTC)

What 'is' I - the amplitude or power - I am confused in that for sensations generally described as 'logarithmic'the exponent seems to be 0.5 ? — Preceding unsigned comment added by 193.34.187.245 (talk) 13:51, 6 April 2018 (UTC)

In English please
Okay, if I have a point source of light physically 100 times brighter than another, how many times brighter will it subjectively look?

What about 2 times, 10 times etc?

I get a feeling the exponent 'a' is like "gamma correction" for a logarithmic scale, am I right?

Please explain the law better. I still don't know how to convert physical and subjective. Sagittarian Milky Way 20:54, 21 April 2007 (UTC)


 * As the article says, it will appear 1000.5 = √100 = 10 times brighter. That is, if I2÷I1 = 100, then the perceived intensity ratio is ψ(I2)/ψ(I1) = kI2α/kI1α = (I2/I1)α = 1000.5.  71.41.210.146 (talk) 03:42, 10 April 2011 (UTC)

Grammar
Move to rename article "Stevens's power law" to more accurately potray ownership. —Preceding unsigned comment added by 69.199.23.90 (talk • contribs) 21:29, 26 June 2009


 * How does "Stevens' power law" not accurately portray ownership? --Darxus (talk) 04:16, 21 August 2009 (UTC)

Logarithmic, yes?
Stevens' power law implies that all perception is logarithmic, correct? Just as the Weber–Fechner law? --Darxus (talk) 04:19, 21 August 2009 (UTC)


 * No; a fixed exponent (as is proposed here) is still polynomial. And polynomials grow more quickly than logarithms, and more slowly than exponential functions.  Using Big-O notation, O(log x) ⊂ O(xk) ⊂ O(ex) for any k &gt; 0 (and base e &gt; 1). 71.41.210.146 (talk) 11:58, 10 April 2011 (UTC)


 * Weber-Fechner is $$dp=k\cdot\frac{dS}{S}$$. Writing Stevens as $$p=c\cdot S^k$$, differentiating produces $$\frac{dp}{p}=k\cdot\frac{dS}{S}$$. The right hand sides are identical, and $$dS/S$$ is objectively measurable. It seems simple enough to design an experiment that distinguishes between the two left hand sides--the first is perceived difference, while the second is perceived difference relative to perceived absolute magnitude. Does the literature clarify the difference between these two? Dave Blau (talk) 16:53, 6 November 2017 (UTC)

Reference for the Exponent Table Needed
Could someone please include the proper citation for the Stevens' exponent table? The line "The table to the right lists the exponents reported by Stevens" does not allude to any correct citations. The only Stevens' original document cited in this article is "On The Psychophysical Laws", which does contain a table of several exponents he proposed but they are not the same as the ones included in the table.

Thank you. Yukino91 (talk) 04:53, 21 October 2011 (UTC)


 * This 1988 book says ref 16, but I can't see what that is. Dicklyon (talk) 05:25, 21 October 2011 (UTC)


 * So this book is the source? I can't open it. It seems to be only about taste, so I wouldn't think it would list the entire table included in this article. Or does it? Yukino91 (talk) 04:46, 26 October 2011 (UTC)


 * Email me if you'd like me to capture a copy of the page and send it back to you. It has the entire table that the article has (at least, the first few and last few lines that I compared).  Dicklyon (talk) 05:23, 26 October 2011 (UTC)


 * Here is a slightly different table, again sourced to a book on food quality. There are also hits for psych books, but I don't find one where I can see the page with the table yet.  I might have one at work...  Dicklyon (talk) 05:31, 26 October 2011 (UTC)


 * This book has very different number for sound. Some are relative to sound pressure and some sound intensity, which makes a factor of 2 differences in the exponent.  Dicklyon (talk) 05:34, 26 October 2011 (UTC)


 * Oh, look, it's from Stevens.

Psychophysics: introduction to its perceptual, neural, and social prospects Author	Stanley Smith Stevens Editor	Geraldine Stevens Edition	reprint, illustrated Publisher	Transaction Publishers, 1975 ISBN 0887386431, 9780887386435 (I had to change Hz to hertz to find it.) I added it to the article refs. Dicklyon (talk) 05:41, 26 October 2011 (UTC)


 * Okay, thank you for adding the source. I had no doubt the information was correct. Me and my professor just didn't know what to make of the lack of the original source for the table. Yukino91 (talk) 06:05, 26 October 2011 (UTC)

Units in table entry
The table specifies the amplitude of a vibration in 60 Hz or 250 Hz. I expect what is meant is that the frequency is 60 Hz or 250 Hz. In this case, the intensity (I) would be the amplitude of the vibration, with a larger amplitude corresponding to a greater stimulus. — Preceding unsigned comment added by Econnally (talk • contribs) 15:29, 16 December 2013 (UTC)
 * Amplitude is the stimulus; the frequencies are two different conditions. Dicklyon (talk) 17:04, 4 December 2017 (UTC)

Merge proposal
This is essentially a copy of Stevens' power law. 81.225.32.185 (talk) 23:37, 23 January 2024 (UTC)
 * No duplication; I think that the proposed was confused by the redirect - there was no duplication. Klbrain (talk) 06:29, 22 February 2024 (UTC)