Month: July 2013

How blind people see

Blind people have revolutionised our view on vision. Biology text books still teach us that vision functions roughly as light hitting the eyes where special cells – rods and cones – turn it into neural signals. These travel to the back of the head, the visual cortex, for brain processing leading to something we experience as ‘seeing’. Some blind people have offered a completely new picture. They see without visual cortex. They see without rods or cones. They see without experiencing ‘seeing’.

Stevie Wonder

Wearing sunglasses might impair vision – in the blind.

The visual cortex lies right at the back of the head and it is – as the name suggests – responsible for vision. If you lose it, you can’t see anymore. This happened to a partially blind patient only known by his initials DB, a man brought to scientific fame in 1974 by an article in the journal Brain. In it, Lawrence Weiskrantz and colleagues describe how DB is asked to say whether he is presented an X or an O in an area of his visual field where he is blind. DB performs more than 80% correct despite only guessing.
What happened when DB was told about his visual abilities? ‘[H]e expressed surprise and insisted several times that he thought he was just “guessing.” [H]e was openly astonished’ (p. 721). This phenomenon has been termed blind-sight and it is very unlike normal vision. It is usually much worse but there are exceptions. For example, DB is actually better at ‘blind-seeing’ very faint lines compared to his intact visual field or normal people’s vision (Trevethan et al., 2007). This rules out all sorts of concerns about blindsight such as the suggestions that DB might be lying or falsely describing degraded vision as no vision at all. Unusually good performance can hardly be faked.
If blind-sight is possible without visual awareness or visual cortex, is it also possible without the eye’s rods and cones which turn light into neural signals? Interestingly, yes. Back in 1995 a team led by Charles Czeisler reported an unusual finding in three blind people whose eyes were damaged due to various diseases. When a bright light was shone in their face, they had less melatonin – a hormone related to the sleep cycle – in their blood. Probably a little known cell type – called intrinsically photosensitive retinal ganglion cells – turned light into neural signals and generally helps us synchronize our sleep-wake cycle with the day-night cycle.
A new article by Vandewalle and collagues shows what the potential of this newly discovered cell type is. They tested three blind people with eye damage and simply asked ‘is there a light or not?’ If a light was on for ten seconds, all three ‘guessed’ significantly differently from chance. This is remarkable as these people reported not seeing anything, electrical brain potentials following light flashes were curiously absent and their eyes were undoubtedly damaged.
When looked at together, these phenomena offer a new picture of the visual system. In the text-books you see a linear picture roughly like this:
light –> rods/cones in the eye –> visual cortex –> rest of brain
A new model is needed because a remarkable range of behaviours can still be performed when the middle elements of this account are removed. Instead of a linear picture we need a collection of parallel pathways all using light to influence the brain. The blind-sight pathway proves that circumventing the visual cortex is possible. People without rods/cones prove that not even these cells are needed to make use of light.
And now imagine that vision is one of the best-understood systems in the brain. If even vision can offer such surprises it is difficult to imagine what other brain systems hide below the surface. However, going ‘below the surface’ also comes with a considerable cost. Ask blind people what they see and they simply say ‘nothing’. Their residual abilities are hidden from them. It takes careful psychological testing to make them aware of what they can do.
So, how do blind people see? Some of them see without even knowing it.

Czeisler CA, Shanahan TL, Klerman EB, Martens H, Brotman DJ, Emens JS, Klein T, & Rizzo JF 3rd (1995). Suppression of melatonin secretion in some blind patients by exposure to bright light. The New England journal of medicine, 332 (1), 6-11 PMID: 7990870

Trevethan CT, Sahraie A, & Weiskrantz L (2007). Can blindsight be superior to ‘sighted-sight’? Cognition, 103 (3), 491-501 PMID: 16764848

Vandewalle G, Collignon O, Hull JT, Daneault V, Albouy G, Lepore F, Phillips C, Doyon J, Czeisler CA, Dumont M, Lockley SW, & Carrier J (2013). Blue Light Stimulates Cognitive Brain Activity in Visually Blind Individuals. Journal of cognitive neuroscience PMID: 23859643

Weiskrantz L, Warrington EK, Sanders MD, & Marshall J (1974). Visual capacity in the hemianopic field following a restricted occipital ablation. Brain : a journal of neurology, 97 (4), 709-28 PMID: 4434190


1) By Antonio Cruz/ABr (Agência Brasil.) [CC-BY-3.0-br (, via Wikimedia Commons

Music training boosts IQ

There are more and more brain training companies popping up which promise the same deal: improved intelligence. While there are doubts about their results, another sort of brain training has existed since the beginning of humanity: music. The evidence for its effectiveness is surprisingly strong.


Music Lesson, 1936

Brain training in the 1930’s.

Over the years, researchers have noticed that people who have taken music lessons are better on a wide range of seemingly unconnected tasks. Just look at this impressive list:


Mathematics (across many different tasks; Vaughn, 2000)
Reading (understanding a written text; Corrigall & Trainor, 2011)
Simon task (quickly overcoming an easy, intuitive response in order to do a task right; Bialystok & DePape, 2009)
Digit Span (repeating a long list of random digits; Schellenberg, 2011)
Simple Reaction Time (pressing a button as soon as possible; Hughes & Franz, 2007)


None of these tasks has anything to do with music classes. What is it that makes music lessons correlate with them? It could just be the socio-economic background: the more well-off or well-educated the parents the better the education of their children, including their music education (e.g., Corrigall et al., 2013). However, one can adjust for these differences with statistical tricks and the general picture is that the family background cannot fully explain the advantage musically trained children have on all sorts of tasks (e.g., Corrigall & Trainor, 2011; Schellenberg, 2011). If not family background, then what is underlying the music children advantage?


Füssli: Liegende Nackte und Klavierspielerin

Brain training in the 18th century. I am referring to the left lady.

Another contender is a common factor making some people good on all sorts of seemingly unrelated tasks and other people bad on nearly any task. This factor is called ‘g’ or general intelligence. An indeed, people who have enjoyed a musical education score higher on intelligence tests than people who did not. This has been shown across the globe: North America (Schellenberg, 2011), Europe (Roden et al., 2013), Asia (Ho et al., 2003†). The consistency across age groups is also impressive: 6-11 year olds (Schellenberg, 2006), 9-12 year olds (Schellenberg, 2011), 16-25 year-olds (Schellenberg, 2006). So, what holds these tasks and music education together is general intelligence. But that just opens up the next question: what causes this association between general intelligence and music lessons?
Music lessons cause higher intelligence
The most exciting possibility would be if music lessons actually caused higher intelligence. In order to make such a claim one needs to take a bunch of people and randomly assign them to either music lessons or some comparable activity. This random assignment ensures that any previous differences between music and non-music children will be equally distributed across groups. Random chance assignment at the beginning of the experiment ensures that any group differences at the end must be due to the whether children took music lessons during the experiment or not. Glenn Schellenberg did exactly this experiment with over 100 six-year-olds in Toronto (2004). Over a period of one year the children who learned to play the keyboard or to sing increased their IQ by 7 points. Children who were given drama lessons instead or simply no extra-curricular activity only increased by 4 points (likely because they started school in that year). A similar study which recently came out of Iran by Kaviani and colleagues (2013) replicates this finding. After only three months of group music lessons, the six-year-old music children increased their IQ by five points while children who were not assigned to music lessons only improved by one point. Across studies music lessons boost IQ.
It is worth reiterating how impressive this effect is. It has been found across three different music teaching approaches (standard keyboard lessons, Kodály voice lessons, Orff method). It has been replicated with two different sorts of intelligence tests (Wechsler and Stanford-Binet) as well as most of their subscales. It even came up despite the cultural differences between testing countries (Canada, Iran).
The take-home message couldn’t be any clearer. Music lessons are associated with intelligence not just because clever or well-off people take music lessons. A musical education itself makes you better across many tasks generally and on IQ tests specifically. No other ‘brain training’ has such a strong evidence base. Music is the best brain training we have.


Eros and a youth

Ancient Greek brain training. I am referring to the gentleman on the right.


Bialystok E, & Depape AM (2009). Musical expertise, bilingualism, and executive functioning. Journal of experimental psychology. Human perception and performance, 35 (2), 565-74 PMID: 19331508

Corrigall KA, Schellenberg EG, & Misura NM (2013). Music training, cognition, and personality. Frontiers in psychology, 4 PMID: 23641225

Corrigall, KA, & Trainor, LJ (2011). Associations Between Length of Music Training and Reading Skills in Children Music Perception: An Interdisciplinary Journal,, 29 (2), 147-155 DOI: 10.1525/mp.2011.29.2.147

Ho YC, Cheung MC, & Chan AS (2003). Music training improves verbal but not visual memory: cross-sectional and longitudinal explorations in children. Neuropsychology, 17 (3), 439-50 PMID: 12959510

Hughes CM, & Franz EA (2007). Experience-dependent effects in unimanual and bimanual reaction time tasks in musicians. Journal of motor behavior, 39 (1), 3-8 PMID: 17251166

Kaviani H, Mirbaha H, Pournaseh M, & Sagan O (2013). Can music lessons increase the performance of preschool children in IQ tests? Cognitive processing PMID: 23793255

Roden, I, Grube, D, Bongard, S, & Kreutz, G (2013). Does music training enhance working memory performance? Findings from a quasi-experimental longitudinal study Psychology of Music DOI: 10.1177/0305735612471239

Schellenberg EG (2004). Music lessons enhance IQ. Psychological science, 15 (8), 511-4 PMID: 15270994

Schellenberg, EG (2006). Long-Term Positive Associations Between Music Lessons and IQ Journal of Educational Psychology, 98 (2), 457-468 DOI: 10.1037/0022-0663.98.2.457

Schellenberg EG (2011). Examining the association between music lessons and intelligence. British journal of psychology, 102 (3), 283-302 PMID: 21751987

Vaughn, K (2000). Music and Mathematics: Modest Support for the Oft-Claimed Relationship Journal of Aesthetic Education,, 34 (3/4), 149-166 DOI: 10.2307/3333641



† Effect only marginally significant (0.05<p<0.1)



1) By Franklin D. Roosevelt Presidential Library and Museum [Public domain], via Wikimedia Commons

2) By Johann Heinrich Füssli: Liegende Nackte und Klavierspielerin, via Wikimedia Commons

3) attributed to the Penthesilea Painter, between circa 460 and circa 450 BC, via Wikimedia Commons