Reviews with all double blind testing?


In the July, 2005 issue of Stereophile, John Atkinson discusses his debate with Arnold Krueger, who Atkinson suggest fundamentally wants only double blind testing of all products in the name of science. Atkinson goes on to discuss his early advocacy of such methodology and his realization that the conclusion that all amps sound the same, as the result of such testing, proved incorrect in the long run. Atkinson’s double blind test involved listening to three amps, so it apparently was not the typical different or the same comparison advocated by those advocating blind testing.

I have been party to three blind testings and several “shootouts,” which were not blind tests and thus resulted in each component having advocates as everyone knew which was playing. None of these ever resulted in a consensus. Two of the three db tests were same or different comparisons. Neither of these resulted in a conclusion that people could consistently hear a difference. One was a comparison of about six preamps. Here there was a substantial consensus that the Bozak preamp surpassed more expensive preamps with many designers of those preamps involved in the listening. In both cases there were individuals that were at odds with the overall conclusion, and in no case were those involved a random sample. In all cases there were no more than 25 people involved.

I have never heard of an instance where “same versus different” methodology ever concluded that there was a difference, but apparently comparisons of multiple amps and preamps, etc. can result in one being generally preferred. I suspect, however, that those advocating db, mean only “same versus different” methodology. Do the advocates of db really expect that the outcome will always be that people can hear no difference? If so, is it the conclusion that underlies their advocacy rather than the supposedly scientific basis for db? Some advocates claim that were there a db test that found people capable of hearing a difference that they would no longer be critical, but is this sincere?

Atkinson puts it in terms of the double blind test advocates want to be right rather than happy, while their opponents would rather be happy than right.

Tests of statistical significance also get involved here as some people can hear a difference, but if they are insufficient in number to achieve statistical significance, then proponents say we must accept the null hypothesis that there is no audible difference. This is all invalid as the samples are never random samples and seldom, if ever, of a substantial size. Since the tests only apply to random samples and statistical significance is greatly enhanced with large samples, nothing in the typical db test works to yield the result that people can hear a difference. This would suggest that the conclusion and not the methodology or a commitment to “science” is the real purpose.

Without db testing, the advocates suggest those who hear a difference are deluding themselves, the placebo effect. But were we to use db but other than the same/different technique and people consistently choose the same component, would we not conclude that they are not delusional? This would test another hypothesis that some can hear better.

I am probably like most subjectivists, as I really do not care what the outcomes of db testing might be. I buy components that I can afford and that satisfy my ears as realistic. Certainly some products satisfy the ears of more people, and sometimes these are not the positively reviewed or heavily advertised products. Again it strikes me, at least, that this should not happen in the world that the objectivists see. They see the world as full of greedy charlatans who use advertising to sell expensive items which are no better than much cheaper ones.

Since my occupation is as a professor and scientist, some among the advocates of double blind might question my commitment to science. My experience with same/different double blind experiments suggest to me a flawed methodology. A double blind multiple component design, especially with a hypothesis that some people are better able to hear a difference, would be more pleasing to me, but even here, I do not think anyone would buy on the basis of such experiments.

To use Atkinson’s phrase, I am generally happy and don’t care if the objectivists think I am right. I suspect they have to have all of us say they are right before they can be happy. Well tough luck, guys. I cannot imagine anything more boring than consistent findings of no difference among wires and components, when I know that to be untrue. Oh, and I have ordered additional Intelligent Chips. My, I am a delusional fool!
tbg

Showing 7 responses by puremusic

Qualia8,

"Far from cleansing the auditory taste of one note from one's mind and then playing another, you need to play them immediately back to back for comparison purposes. Perhaps you can switch the order around to eliminate after-effects"

Switching the order around doesn't eliminate after-effects, it only replaces one "smeared" event by another; possibly different from the first. For example, if you follow a yellow image by a red one, the complementary after-image of yellow (violet) will "combine" with red. If you switch the order and show red first, followed by yellow, then the complementary after-image of red (green) will "combine" with yellow.

Best Regards,
John
Hi Pabelson,

"But they've also discovered that, once you've learned those differences, the best way to confirm that those differences are really there is through short-term listening tests that allow you to switch quickly between the two components."

Any neuroscientist who would claim he/she discovered "the best way" to confirm differences would not be very credible with me on at least two counts. First, it is the "best" amongst which collection of methods? Have ALL POSSIBLE methods been tested? Perhaps some heretofore untested method could be even better. So, the scientist overstated the result. Although such hyping occurs, it is hardly scientific. It would also lead me to question if the scientist's methods also lacked precision and other high scientific standards.

Second, to determine that this method is the "best", it must be different from the rest. But how can the neuroscientist determine this difference? By DBT, the "best" method that determines differences??? But then the neuroscientist will be using the very method he/she is attempting to validate. In other words, the neuroscientist would hang himself/herself in a logical loop of circular reasoning.

Your statement appears to be based, at least in part, on faith in neuroscience and psycho-acoustics. These are important sciences but they are not hard sciences like physics and chemistry. Compared to physics, they are sciences in infancy. Their levels of rigor, accuracy, predictability, and reliability are not yet in the same league as those for physics and chemistry. So, my level of confidence in them is not as great as what yours appears to be in your posts. It's the complexity.

The complex substratum involved in auditory perception is not yet sufficiently understood to shed light on the finer aspects. A large number of neurons form millions of possible pathways that a particular "encoded song" can travel in our brains to yield the perception of its sound and our reaction to it. The same song or piece of music produced by the same audio system a few moments later may not travel the exact same pathways in our brain and hence may produce a different experience. This variability is compounded by the non-constant chemical environment that influences our experience. (For example, the amount of endorphins available at any one time.) Emotional changes, expectations, suggestions, levels of alertness, fleeting nature of memory, etc. add to the variability. Also, the brain circuitry is not as rigidly set as it once was thought to be. It can change with experience and learning. At the current state of neuroscience, there is insufficient organization, understanding and integration of this variabile milieu to shed light on the finer issues about DBT. That may be reason enough for some opponents of DBT to claim that "to DBT or not to DBT" is an irrelevant question. I, for one, am in favor of rigorous DBT and would find the positive results useful but the negative results inconclusive for reasons given in my previous post.

Best Regards,
John
For the record, I am not opposed to rigorous DB tests; they can provide useful information. However, I do NOT have a high level of confidence in definitive interpretations of a negative result of a short-term DBT involving 2 components that may have subtle differences. As noted in my previous posts, the underlying complexity has not been unravelled yet.

I'll try one last time to hint at the complexity involved. In wine tasting, if you taste two samples one after the other, you should rinse the mouth with water to minimize the influence of the "after taste" of the first sample on the second one. If you look at a bright yellow object and then close your eyes, you will see an "after image" of a complementary color. As long as that "after image" persists, it is a "noise" that may influence some subtle subsequent visual experiences. Our brain circuitry and chemistry is not like electronic circuitry. I does not start and stop with the stimulus; and it has it's own variable "noise floor". The "after effect" that persists may mix with the subsequent stimuli. This added "noise" may smear the more subtle characteristics. A SHORT-TERM DBT may not allow enough time for the "after effect" of the previous sample to subside. That "noise" in the neuro-biological environment may smear SUBTLE differences.

Those of you with high level of confidence or faith in the negative results of short-term DBTs have yet to address this and other complexity issues. Hopefully, these issues will be sufficiently addressed as neuroscience and psychoacoustics develop. The reason why tremendous amount of research is still going on is because there is a lot that is not yet known. At least not enough is known for me to be very confident.

In the meantime, a rigorous DBT, among other things, should: 1)provide sufficient time between samples; 2) reduce the room effect that may smear differences; 3) make sure the participants pass a comprehensive hearing test, demonstrating that they can hear the frequencies in the audible range and can percieve dynamic gradations; 4) make sure the tested material includes a full spectrum of frequencies and a large variety of harmonic textures and dynamic shadings; 5) adjust the level of sound, preferably without adding any other components into the signal path that may smear differences; etc. After all, a meta-statistical analysis on a lot of flawed DBTs is not good science.
Hi Phredd2,

You asked for some additional elements for rigorous methodology. In addition to the acuity tests I mentioned previously, participants should pass reasonable memory tests. Otherwise, their inability to distinguish 2 amps may not be a statement about the amps but about the participants. It is fine with me if an audiophile wants to listen privately just to see if he/she likes or prefers a component. But this is not acceptable for rigorous testing. Therefore, participants should be able to demonstrate their critical listening skills. If they aren't accustomed to listening consciously for nuances in harmonic textures, changes in micro-dynamics, phrasings, ambience, decay, etc., then they may miss subtle differences in how 2 amps reproduce the different musical elements.

"After-effects", as pointed out in my previous posts, are inherent to our perceptual mechanisms and brain circuitry/chemistry and may smear differences between 2 components in a short-term DBT. Consequently, a negative result of a short-term DBT may have an interpretation other than "no difference in the amps". Allowing enough time for the "after-effects" to subside, is one way to reduce their effects. However, this may add to some degradation of memory, as pointed out in one of the posts above; but that just re-inforces my contention that the underlying complexity has not been unravelled enough yet to make definite determinations. Please see my exchanges with Qualia8 for additional comments.

Great Listening,
John
Hi Pabelson,

You did not address some critical issues I raised in my posts. In particular, that the "after effects" of sensory experience can combine with subsequent stimuli to smear differences. The "after effects" result when the brain circuits don't start and stop with the the stimuli. If you continue to evade by brushing aside the issues, then there is no reason for me to continue with this thread.

Best Regards,
John
With apologies to Shakespeare and all logicians:
"To DBT or not to DBT is or is not the question."

Hi Pabelson,

Your quote points us to the central point of this discussion:
"Yes, beauty can grow on you. But notice that it's not the lady who's changing. It's you. What does that tell us about long-term comparisons?"

It tells us what neuroscience has discovered. The brain is much more plastic than once believed. It is not static like electronic circuits. The brain circuitry and its chemistry change. New interneuronal connections are formed and concentrations of neurotransmitters and other brain chemicals change. So, what the brain could not distinguish one day, it may LEARN to distinguish in subsequent exposures to the experience. We have experienced this learning phenomenon as students, as professors, and as audiophiles. This is part of our growth and evolution. A double-blind test based on short-term listening sessions may not allow enough time for the brain circuitry and chemistry to reconfigure itself to discern the difference. Therefore, if a short-term double-blind test does not show a difference between two amps, it would not be correct to conclude that there was no difference between the amps, only that that particular test did not reveal a statistically significant difference. A double-blind test showing a positive difference may be useful for audiophiles, while the test showing no difference is an inconclusive statement about the amps.

Incorrect interpretations can also be made for long-term double-blind tests. History of science shows us that even the hard sciences like physics are not immune from making incorrect interpretations. A committment to truth and critical thinking helps purify science to better the human condition. Otherwise, our implicit assumptions may yield tautological statements similar to the very first statement in this post. Although it is logically valid, it does not contain useful information for the audiophiles.

Best Regards,
John
Qualia8,

There is a vast array of specializations among the neurons in the brain. Some, as you pointed out, detect differences, others sameness; yet others, change or motion or timing, etc. Ignoring that complexity, may lead both sides of this discussion to over-simplification at best and to closed-mindedness at worst.

With that in mind, let me add the flip side to my previous post to you. The after-effects may not only smear differences, but they may also distort sameness. Take for example the two abstract amorphous paintings containing a rich array of colors in my living room. Everyone who looks at either one, reports the same phenomena. The colors change, the amorphous shapes change and those shapes move. Now, we know the painting remains the same. The changes are the result of the brain's processing. It appears the after-images of the various colors "combine" with the direct stimuli to produce a change in the perception, which in turn forms it's after-images which "combine" with the subsequent direct stimuli, etc. What follows is a sequence of illusory changes which create a dynamic that is not there.

This perceptual phenomena of after-images has been studied but it has not been eliminated. The temptation to reduce it's effect by taking micro-second intervals of music, automatically prejudices the methodology against percieving differences that require longer intervals; for example, decay and rhythm.

The debate with probably go on. In the meantime, it's good to have a discussion that produces more illumination than heat.

Enjoy the Music,
John