Joy, Guilt, Anger, Love (10 page)

The truth of context

It is entirely disputable whether Caravaggio in truth felt any guilt. There is no way to find out. In light of his turbulent past of crime, brawls and violence, he may well have felt none. The fact that he used his own face to depict Goliath is no definite proof of his feelings of remorse. There are no documents or letters that may testify to an authentic repentance. Some argue that his portrait as Goliath is yet another expression of his narcissism.
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The painting may have been just the artist’s nifty stratagem to regain credibility and have the gates of Rome opened to him again. Caravaggio had the painting sent to a powerful patron in Rome, the Cardinal Scipione Borghese, the administrator in chief of the Vatican system of justice, to seek forgiveness and permission to re-enter the city from which he had fled in disgrace.
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Caravaggio’s undeniable talent, his boundless imagination and his sensitivity may have enthralled anyone willing to give him another chance. If his goal was to convey a deep sense of guilt and his repentance, he did succeed in it. He certainly knew how to conquer the viewer’s sympathy with the emotional power of his paintings.

We need to pay attention to the historical context of the painter’s life. In Caravaggio’s Rome, murders were not a rare occurrence. The prevailing customs and squalor of the city were such that fights, or even homicides, happened on a regular basis. Rome was a daily circus, a rowdy and perilous place. This does not mean that in Rome at the turn of the seventeenth century murders were encouraged, or that they would go unpunished. But they were frequent. The anatomical precision and realistic immediacy of the physical violence in Caravaggio’s paintings reflected first-hand knowledge of the violence to which he was exposed on the streets.

What makes emotions such as guilt and shame moral is also their dependency on given values of the social context. As a moral emotion, guilt is influenced by the behavioural codes and norms of the culture in which it is experienced. Actions or turns of speech that are considered inappropriate in one culture are guilt-free in another culture. In the UK, homosexuality was not decriminalized until 1967. For almost all religions, it still remains an unacceptable sin, and several countries in the world, such as Uganda or the United Arab Emirates, continue to ban it.

Today, killing someone would never be regarded as an acceptable custom or a forgivable deed (though, that said, there are countries that inexplicably retain the death penalty). However, when judging the severity of a murder, courts take into account elements that may justify the killing – say, legitimate defence. In countries such as Italy, crimes of honour were customarily punished with lenient sentences until the early 1980s. If an action is not frowned upon or considered illegal in a particular society or social context, those committing it experience no habitual response of guilt. The biological apparatus that can make us feel guilt is spared the expenditure of energy. So, morals and norms evolve and change in society, and our biological ability to make moral choices and feel guilt over them adapts accordingly.

Caravaggio eventually received the Vatican’s pardon, but he never reached Rome, for he died in mysterious circumstances on his way back to Rome.

If Caravaggio were still alive today, he would certainly make a very interesting subject for neurological study: both in further investigation of the neural seat of guilt, and a thorough scrutiny of his extensive portfolio of violent and rebellious actions. Was he a carrier of the short version of the MAOA gene? What did his prefrontal cortex look like? Did his solitary childhood and dismantled family play a role in the outcome of his violent behaviour? The answers blow in the wind.

But the incomparable calibre of his art, his enhanced imagination and his capacity to trap a fleeting rainbow of emotions on canvas persuades me that he must have felt unease and discomfort after committing the murder and that guilt cannot have left him unscathed.

What’s in a blob?

To compare a brain scan with a Caravaggio painting in the search for the most authentic representation of guilt may be novel or sound unusual to you. Take a look at both images again. First, examine the blob in the fMRI image, and then gaze at the painting. Both are supposed to represent the emotion of guilt. They are powerful images, each in its own way. The scan is extremely technical and hard to make out, if you are not familiar with brain anatomy. Where is that dot exactly, if you were to imagine it in your own head? The painting is undeniably intense, extremely sombre, but also requires knowledge and interpretation beyond the immediate, communicative strength of its treatment of light. Nevertheless, they both entice a viewer’s attention.

Attractive images of the brain, especially scans of someone experiencing guilt or other emotions, abound. Emotions are mediated by brain activity. Just as it is useful to observe the outer appearance of emotions, in facial expression, skin conductance response or body movements, inspecting the brain reveals fundamental components of emotions.

The greatest advantage of functional magnetic resonance imaging is the possibility of watching the brain without having to open the skull. Earlier, in order to inspect the brain’s turns and grooves, you had to drill down through the skull or examine the brain outside the body. Now, we can watch what goes on inside while the brain is engaged in all sorts of tasks. More than a snapshot, an fMRI image is a still from a movie. It aims at capturing brain workings in space and time. This is certainly an incredible and unprecedented privilege. However, there is still a problem of refinement.

A detailed, thorough explanation of what happens when you enter the large fMRI scanner would involve going into details of complicated engineering and quantum mechanics. But even without a degree in physics, it is possible to grasp the essential features of this technique and to understand both its power and its limitations.
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First of all, it is not entirely correct to say that the colourful blobs that stand out against a grey, blackish background in a brain scan are direct signs of brain activity. The blob signal on an fMRI scan, however narrowly localized it may be, is primarily telling us that there is a lot of oxygen in that area, brought in by the flow of blood, which we assume is needed by neurons to be able to function, just as more blood rushes to the stomach during food digestion for the absorption of nutrients.

Basically, if a part of the brain is needed to accomplish a given mental task – say remembering a seven-digit number, which keeps the prefrontal cortex busy – it will require energy to carry it out. Where does the energy come from? Like muscles, to carry out their work neurons need sugars, such as glucose, which are broken down in the presence of oxygen.
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The oxygen is rushed to that site through the haemoglobin carried by blood. In effect, what is being detected during an fMRI session is the ratio between the amount of oxygen brought in and the amount of oxygen used up for the task, as signalled by the presence of oxygen on the haemoglobin molecules in that area. The oxygenated and non-oxygenated forms of haemoglobin have different magnetic properties – the protons in their atoms behave differently – and this difference is picked up by the huge magnet of the scanner (the magnetic properties of haemoglobin were discovered back in the 1930s by the great scientist Linus Pauling!).
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In laboratory parlance, this difference is called BOLD (short for ‘blood oxygen level dependent’) contrast. So, what the brain scanner picks up are incredibly tiny differences at the subatomic level of blood.

As you would expect, glucose and oxygen are needed across the entire brain, including areas that are not engaged in any particular task. There is a great deal of background activity the brain carries out without our realizing. What fMRI does is either to map the location during a specific task of any progressive increase in oxygen relative to levels of oxygen in a control quiet state (also called the
baseline
, or default state, where the brain under scrutiny is at rest), or to measure the difference between changes in oxygen during two different tasks. fMRI is basically looking for and detecting alterations, the additional activity that is associated with the task. So, for instance, in the experiment looking for the seat of private conscious guilt, the signal detected showed alterations in activity between moments of guilt recollection and a baseline state, as well as differences between recollections of guilt and shame, or guilt and sadness.

Seeing is believing

Neuroscience holds enormous allure for the non-expert public. A study found that the same neuroscience result was regarded by non-experts as more credible if it was represented by the image of a brain scan than if it was presented with a more traditional bar graph or no image at all.
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Seeing is believing. Perhaps brain scans are more persuasive because they offer a physical explanation. They are seductive in that they increase the plausibility in the eyes of the general public of conclusions presented by researchers. They have become icons comparable to X-rays and the DNA double helix in their importance and resonance in our culture. They are found on the covers of books about the brain, in tube ads, in promotional literature for corporate and managerial courses that are supposed to improve performance.
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As Susan Fitzpatrick reports, in 2005, at a meeting of the American Association for the Advancement of Science, a panel session organized by the James S. McDonnell Foundation was given the provocative title: ‘Functional Brain Imaging and the Cognitive Paparazzi: Viewing Snapshots of Mental Life Out of Context’.
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The analogy between the work of brain-imaging scientists and that of aggressive photographers avid for a scoop may sound at first unusual or slightly off-beam, but it does have a point. What paparazzi do is to steal intimate, private moments of celebrities and then publish them on tabloid front pages. The raw pictures are ‘repackaged’, revisited and extracted out of their wider original context so that, with the help of juicy misleading headlines, the snapshots of an occasional long face, a solitary walk in the park or unusual weight-loss are sold as evident signs of depression, an imminent divorce or hidden eating disorders. Through powerful magnetic field scanners, cognitive scientists also capture private instants of our mental life. They certainly have no intention of gossiping, nor of falsifying their data, but again, the resulting pictures are mere extracts of the mind. When fMRI images hit the newspaper headlines, they too are taken out of context, out of the laboratory setting where they were produced.

I mentioned earlier that fMRI imaging attempts to capture the workings of the brain in space and time. Some remarks about scale need to be made in this regard.

Time is a critical issue. The speed of blood flow in the brain is measured on a scale of seconds, whereas the subtleties of neuronal activity are hundreds of times faster. So there will always be a certain time-incongruence in the correspondence between neuronal activity and blood-flow dynamics.

Each fMRI image is a colourful, computer-generated map resulting from the comparison of signal intensities across the various regions of the brain. Each little dot composing the image is called a voxel – which is more or less like the pixels that make up your iPad photos, but is a three-dimensional unit of volume, rather than a two-dimensional unit of flat space. What you see is a shade of colour, a tiny pinned spot in the human brain, but behind it lies a vast complex of neural tissue and neurochemical reactions. Each voxel corresponds to approximately 55 cubic millimetres. This equates to around five million neurons, with anything between twenty-two billion and fifty-five billion synapses, which are the points of connection between neurons. If stretched out, the distance covered by the ramifications of the neurons involved would roughly correspond to the distance between, say, London and Manchester.
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Scientists perform complicated statistical and numerical operations across that vast territory of neurons captured in the scan. Each voxel is compared with all the others, in search of meaningful information. The shadings in colour intensity are a reflection of the statistical significance of the measured differences. The more intense the colour, the more significant the change in haemoglobin oxygen detected. In 2012, a rather bizarre study showed some of the dangers of such statistical comparisons in fMRI. For its originality and improbability, it even won the IgNobel Prize for Neuroscience – the annual counterpart of the real Nobel Prize, which praises discoveries that ‘first make people laugh, and then make them think’.
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The humour is inevitable because of the study’s unique feature: its only participant was a dead salmon.
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The researchers placed it in an fMRI scanner and showed it images of individuals engaged in a variety of emotional scenarios. The salmon was then asked to report which emotions each individual was experiencing – I confess I would have loved to be there when the experiment took place. As expected, they received no answer from the salmon, but the researchers identified neural ‘activity’ in the salmon’s brain and spinal cord! How was this possible? The authors remark that as thousands of comparisons between one voxel and the others are made during each fMRI data analysis, there is a high chance that false positives will emerge. You may see stuff that you are actually not supposed to see. There is absolutely no way that a dead salmon could have recognized emotions.

There are methods in statistics that help ‘correct’ for such mistakes. In fact, when the authors applied those correction methods, the blob in the salmon’s brain vanished from their analysis. The dead salmon researchers reported that while such methods are available as part of most fMRI analysis software packages, not every research team applies them, because correcting for false positives may reduce the statistical power of their analysis. They found that, for instance, in 2008, the correction methods had been used in only 61.8 per cent of the papers appearing in the
Journal of Cognitive Neuroscience
, one of the many journals in which fMRI results are published. So, absurd as it was, the salmon experiment highlighted a frequent methodological negligence in the production of brain-imaging data.
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