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In Defense of Electroconvulsive Therapy October 30, 2007

Posted by Johan in Abnormal Psychology, Applied, Emotion.

Blogging on Peer-Reviewed ResearchThe TED talks website contains material for a hundred posts, but a video posted earlier today hits particularly close to home. In this talk, Sherwin Nuland, a surgeon turned writer, gives an authoritative and unexpectedly personal account of the history of electroconvulsive therapy (ECT), sometimes known as electric shock therapy. The talk is only about 20 minutes, and gets very interesting around the 7 minute mark where Nuland describes how ECT once saved his life, as he puts it.

If the general public could be accused of placing too much trust in antidepressant medication, the reverse is certainly true of ECT. Ask anyone about electric shock therapy, and they’ll conjure up horror stories, and associations with frontal lobotomy. This is unfair, since there is some evidence that ECT actually works for depression.

The research on this issue has produced mixed results and plenty of controversy, as reviews by Challiner and Griffiths (2000) and by the UK ECT Review Group (2003) outline. However, there is no shortage of positive findings, and this in itself is rather remarkable, when you consider the patients that receive it. Since ECT is considered rather drastic, it is only really considered for patients who are severely depressed, and who have failed to respond to antidepressants. In other words, ECT is usually only considered in cases with the worst possible prognosis, so the fact that it does seem to help at times is quite powerful in itself, given the probability of spontaneous recovery from such conditions. That being said, a read of the ECT literature is unsatisfying. Because ECT is viewed as such a dramatic intervention (even in the absence of evidence that it causes long-term harm), it has rarely been tested on “normal” depressives in random control trials.

As Challiner and Griffiths (2000) outline, a lot of the popular conceptions of ECT are untrue. It doesn’t cause massive spasms – muscle relaxants are administered. It is not going to be a traumatic experience, because you will be put under a general anaesthetic. Although bilateral administration of ECT has been associated with memory loss, this does not appear to happen with unilateral administration, where both electrodes are kept on one side of the head (as shown in the picture at the top).

There is another issue with ECT, which I think bothers practitioners than clients. In the case of antidepressants, we at least know how they work, although it is far from clear why boosting synaptic Serotonin levels should work, given the weak evidence for a lack of Serotonin in depression. With ECT, there are no convincing explanations for either the how or the why. Psychiatrists stumbled upon ECT in the happy days of wild experimentation that preceded Ethics Committees, without much of a theory. It is quite embarrassing that even to this day, we can say so little about what this treatment does, or indeed if it even does anything at all – a pertinent question given the claim on Wikipedia that 1 million people receive ECT each year worldwide.

If I ever developed a severe depression, I would try ECT before antidepressants. Unlike antidepressants, the effects of ECT can be instantaneous, and there are no long-term side-effects, nor any withdrawal symptoms when the treatment ends. Since the treatment is extremely safe when administered properly, there is really very little to lose.

Challiner, V., and Griffiths, L. (2000). Electroconvulsive therapy: a review of the literature. Journal of Psychiatric and Mental Health Nursing, 7, 191-198.

The UK ECT Review Group. (2003). Efficacy and safety of electroconvulsive therapy in depressive disorders: a systemic review and meta-analysis. Lancet, 361, 799-808.


Visual Cortex: A Schematic Map October 22, 2007

Posted by Johan in Neuroscience, Sensation and Perception, Social Neuroscience.
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I came across this figure in a review by Grill-Spector and Malach (2004). It condenses an already-dense 40-page review into a single figure, so I would have to write a post of similar length to explain it entirely in laymen’s terms. This may be one post to skip if you haven’t the slightest idea of visual perception.

Even if you know your vision, this figure isn’t entirely straightforward. Still, I think it serves as a useful reference for those dense vision papers. With one or two notable exceptions, vision scientists insist on ridiculous naming conventions (the motion sensitive area hMT+ being the case in point), so this might help you remember the plot.

This map is only schematic. However, it represents the rough relationships, as they stood in 2004. The areas are mapped onto the right hemisphere occipital lobe, which has been flattened so that the dark areas represent sulcii (grooves), and the light gyrii. The posterior-anterior axis is sort of bottom-left to top-right, so V1 is (predictably) at the very back of the brain, while the Parahippocampal Place Area (PPA) is on the ventral (bottom) side.Height in this picture represents hierarchy in the processing, as Grill-Spector conceives of it. In other words, the first area is V1, and then we move up the stairs to V2, V3, and so on.

The colours code specialization. In the early areas (V1-V3), this is represented by central versus peripheral mappings, where the cortical magnification factor ensures that the centre is largest, and the highest acuity. Helpfully, they are labelled P-D (down) for the superior end of each map, and P-U (up) for the ventral end (your retinal image of the world is upside down, and apparently the visual system has no need to reverse this representation in later areas).

In later areas, the areas are filled in with one colour, presumably for simplicity – Grill-Spector actually believes that these have some retinotopic organisation as well. The colours still reflect specialization though – we can see that areas such as the Fusiform Face Area (FFA) and the Lateral Occipital complex (LO) are based on central, high-acuity representations, while other areas such as the PPA are based on more peripheral, lower-resolution representations. The letters that are strewn over the areas are meant to approximate locations of sensitivity to certain object categories: places (Pl), objects (O), and faces (F).

Do note that the Superior Temporal Sulcus (STS) is treated as somewhat of a black sheep, placed out in the corner with no colouring or height. This is probably because it is relatively poorly understood. The STS responds to biological motion, such a Johansson figures (see a demo), but its activation also appears to be strongly modulated by the social significance of the stimulus. For instance, Pelphrey et al (2005) found that the STS response in normal controls was greater when a face looked away from an obvious object rather than when gaze was directed towards it, which suggests that the STS does more than merely detect biological motion. Interestingly, people with Autism failed to show the same modulation by expectation in the STS.

The poor understanding of the STS is in part because it responds so specifically to biological motion, which makes conventional retinotopy techniques impossible. Also, I suspect there is a deep-rooted fear in some vision scientists of anything that starts with “Social.”

Another thing to note is the chasm between the last V area and the STS. Presumably, the intermittent areas are also involved in vision, but we don’t know much about what they do yet.

Grill-Spector, K, and Malach, R. (2004). The Human Visual Cortex. Annual Review of Neuroscience, 27, 649-677.

Pelphrey, K.A., Morris, J.P., and McCarthy, G. (2005). Neural Basis of Eye Gaze Processing Deficits in Autism. Brain, 128, 1038-1048.

Hearing limitations, pt. 2: Distinguishing MP3 from CD October 16, 2007

Posted by Johan in Applied, Sensation and Perception, Social Psychology.
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As a continuation of the recent post on audiophiles, let’s look closer at how good we are detecting the compression in digital music formats.

Most music formats, such as MP3 or the AAC format used by iTunes, define the rate of compression as the number of bits that is used to encode each second of music. The standard bitrate, as used by the iTunes Music Store and elsewhere, is 128 kbit/s. Music geeks (myself included) tend to use slightly higher bitrates, while the proper audiophiles use lossless formats that compress the file without actually removing any information. Recently, Radiohead released their new album as a free download, only to experience some fan backlash for their choice of a 160 kbit/s bitrate. Critics bemoaned the fact that this was half as much as the 320 kbit/s rate that is used on the mp3s available for purchase on their website. By comparison, the bitrate of a normal audio CD is approximately 1411 kbit/s, so clearly a lot of information is removed.

But can you tell the difference? I dug out a few non-peer-reviewed sources to get an idea – if someone knows of peer-reviewed studies into this, I’d be interested to hear about them. The most serious source is probably this 1998 report from the international organisation for standardisation (PDF), which reports some evidence that participants could distinguish 128 kbit/s compression from the original, uncompressed source. Unfortunately, no tests were made above 128 kbit/s. More recent, but less rigorous tests have been reported by Maximum PC and PC World.

Maximum PC elected to report their results participant-by-participant, and with a sample size of 4, maybe that’s just as well. There isn’t enough data reported in this article to actually run a binomial or another significance test, but the overall conclusion seems to be that none of the testers did well at distinguishing 160 kbit/s from the original source.

PC world’s test actually contains some descriptives, and used a sample size of 30. However, they used some fairly obscure ways of reporting their results. Clearly, in a case like this one, the optimal method is to ask the participants to guess which file is the mp3 and which is the cd, and run a number of trials without feedback. With this approach, you can easily assess whether performance is over the level of chance (50%) for each bitrate. With this in mind, here are their results:

The percentages represent the proportion of listeners who “felt they couldn’t tell the difference” – once again, this measure is far from ideal. While we have no idea which of these differences are significant, the trend is that the differences in ratings flatten off: there appears to be no difference in quality between 192 kbit/s and 256 kbit/s, and in the case of MP3s, no real difference between 128 and 192.

These studies aren’t exactly hard science, they do seem to indicate that those complaining about Radiohead’s 160 kbit/s bitrate wouldn’t necessarily be able to distinguish it from CD quality, let alone a 256 kbit/s mp3. This illustrates the human tendency to overestimate our own perceptual ability – if we know that two things are different, we will find differences, imagined or otherwise. Blind testing is the only way to establish whether a genuine difference in sound quality exists, yet, this is very rarely done.

If you want to test your own ears, try these examples. With the above in mind, it would be best to get a friend to operate the playback, so that you can’t tell from the outset which file is which. If you run a large number of trials, you can also look up whether your performance is above chance in this Binomial probability table. In psychology, .05 is the commonly accepted p value, so as an example you would need to get 15 out of 20 trials correct for your performance to be significantly better than chance at this level.

Update: Dave over at Cognitive Daily has answered my prayers by carrying out a nicely designed test of performance at discriminating different bitrates. In a nutshell, his results confirm the ones reported here – Although there participants rated the 64 kbit/s tracks as significantly poorer in quality, no differences appeared between 128 and 256 kbit/s. Read the complete write-up here.

Audiophiles and the limitations of human hearing October 13, 2007

Posted by Johan in Applied, Sensation and Perception, Social Psychology.

The other week Gizmodo posted an amusing rant about a set of $7250 speaker cables, and the gushing review they received. Among other things, the reviewer referred to the cables as “danceable.” James Randi soon popped around to offer his $1 million prize to the cable company, if they could prove that their cables outperform “normal” Monster cables in a double-blind test.

This is actually an issue of the limits of human perception. Is it really possible to tell the difference between normal high-end equipment, and equipment that veers into the audiophile range? It’s clear that according to many audiophiles, the answer is going to be yes. Wikipedia informs us that there are actually two schools among audio enthusiasts: the objectivist school, which favours double-blind testing, and subjectivists, who favour a more philosophical approach. The review that caused so much ire comes from Positive Feedback, an online magazine that concerns itself with the “audio arts” – guess which school they subscribe to.

Among subjectivist audiophiles, there is a belief that almost any change to the stereo setup results in a perceptible difference in sound. This results in bizarre behaviours, as in this picture from the Positive Feedback staff page:

Note how the speaker cables are carefully propped up on stilts to keep them off the floor, and how what looks like power amplifiers are propped up on massive slabs of wood (I can assure you those didn’t come from the local lumberyard). Another nice example comes from an article in Hi-Fi magazine Masters on Video and Audio:

“The [product] tightened up the sounds of a wide variety of equipment, the improvements often most noticeable in the bass. Imaging and focus usually improved, as did the interstitial quiet, which raised the level of overall palpability, air, and transparency.”

The product? Shelves.

There is one obvious objection to raise here: judging by the pictures of the reviewers on sites such as Positive Feedback, most of them are in their 40’s and beyond. As the following figure shows, this spells trouble:

I grabbed this from a lecture handout, so unfortunately I don’t know the source. The lines plot performance at detecting sounds over age, with each line representing a frequency. In this case “hearing level” is a standardised measure where normal hearing is at 0 dB. The clear pattern is that the higher frequencies disappear with age. This figure only goes up to 6 khz, but it’s worth noting that the human ear can hear up to 20 khz, and that the loss is more dramatic the higher up you go.

In other words, it’s not really worth trusting an audio reviewer who is older than you are, because there is a range of higher frequencies that you can hear while they cannot.

Apart from the overall lack of evidence and the sheer physical implausibility of some of the products, there is some classic research in social psychology that have implications for this topic.

Cognitive dissonance theory was primarily developed by Festinger. Briefly, the idea is that when the individual finds himself in a state where internal beliefs conflict with reality, there is dissonance, which is an unpleasant state. The individual may then employ a number of mechanisms to get around the dissonance, ranging from simply acknowledging that the beliefs were wrong to attacking the reality of external events, or devaluing the conflict.

The classic cognitive dissonance study is one where students perform a dull experiment, and are then paid a small or a large amount of money for telling the next participant that the experiment is actually fun (Festinger & Carlsmith, 1959). Surprisingly, students who are paid less actually rate the dull task as more interesting. In this case, the student finds himself (all males in Psychology studies in those days, generally) in a conflict: he has just done a boring experiment and lied to a fellow student for a very small reward. According to Festinger and Carlsmith, the student then reduces dissonance by re-evaluating the task. If the task was actually fun, then there is no dissonance between the student’s actions and beliefs.

The implication for consumer behaviour is that when your green $7250 cables arrive in the mail and you plug them in, finding that they do nothing would result in unacceptable dissonance. In fact, cognitive dissonance theory predicts that the more you pay for the cables, the more inclined you will be to conclude that they sound good, regardless of the actual quality of the cables. In this context, it is worth noting that the Positive Feedback website states that their policy is that reviewers should own the equipment they review, which is a very unusual policy in light of cognitive dissonance theory.

There is another classic social psychology study that is relevant here: Sherif’s investigation of the autokinetic effect (1935). To observe this effect, place yourself in an absolutely dark room with a single, faint light source. The spot of light will appear to move around as a result of small eye movements that your brain normally filters out. Sherif’s participants didn’t know about this however, so they really thought the light moved.

When the participants rated when the light moved individually, there was considerable variation between the participants in how far the light moved. Sherif then placed participants in groups and asked them to call out the movements of the light. Now, there was a convergence effect, so that the estimates of the different participants came closer to each other, and remained close in subsequent individual re-tests.

If you and your friend are listening to a new stereo and she mentions that the low bass sounds a bit flat, you are going to hear it too. The sound itself is ambiguous, not to mention the terminology that audiophiles use, so Sherif’s study suggests that in such situations, you will align with the group. You can imagine that this tendency to conform is quite useful in many real-life contexts, but it does mean that wine sampling and stereo testing are unlikely to reflect anything other than your tendency toward conformity. That doesn’t mean it can’t be fun, of course.

You can test this out yourself if you ever find yourself at a wine sampling. Make up associations: say the wine tastes like blackcurrant (always a a winner), sandal wood, tobacco, myrrh. As long as your ideas aren’t too far off, you will find that others suddenly experience the taste too.

While our senses are rather limited, our ability to fool ourselves is almost endless.

Festinger, L., and Carlsmith, J.M. (1959). Cognitive Consequences of Forced Compliance. Journal of Abnormal and Social Psychology, 58, 203-210.

Sherif, M. (1935). A study of some social factors in perception. Archives of Psychology, 27.