Brain plasticity -- why should intelligence be an exception?

We live in an age that demands we multitask if we're going to get everything done that we need to do.  Answering email, picking up the children, submitting grants for every deadline, getting in 30 minutes of exercise everyday, eating right, keeping up with the literature -- so much pressure.  Fortunately someone's got our backs, and we can now answer email on one screen at our treadmill desks and work on that grant proposal on another, all while we have lunch.  So much easier, so much time saved.

But wait, psychology tells us that, despite appearances, we can't multitask after all, we can't do two cognitive things at once.  Instead we're 'task-switching', reading then speaking, writing a paragraph then answering the text from the child we forgot to pick up. So tread milling, eating and emailing we can do but tread milling, eating, emailing and writing a methods section we can't.

Unless we're musicians.  A new paper in Cognitive Science ("Musical Training, Bilingualism, and Executive Function: A Closer Look at Task Switching and Dual-Task Performance," Moradzadeh et al.) reports that musicians are better at task-switching and 'dual-tasking' than non-musicians.  Task-switching is just what it sounds like, the ability to switch between tasks, and the speed and ease with which this can be done is what was measured.  Dual-tasking is the ability to do two or more things at once. There must be a reason this isn't just 'multi-tasking' but I don't know what it is.

I'm also not sure what constitutes a 'task'.  Indeed, how many tasks is reading music, with all the separate bits it involves (remembering which key has 5 flats, how long to hold a black flagged note compared with an empty oval, what that marking over the final note means, all the Italian notations telling you how to play the piece, turning notes on a page into a melody, keeping time, etc.) or playing the horn, with all the separate bits that involves (how to blow into the mouthpiece, how to press the keys, which fingering to use for each note and how to do that, how to synchronize your breathing with your fingers to get a note, how to play loudly or softly, playing in tune, all while remembering what each of the conductor's hand movements signifies, and staying in time with the players around you)?  Some of these tasks get relegated to muscle memory after enough practice, certainly, but much of musicianship still involves cognition.

Anyway, the researchers compared the ease with which a group of 153 bilingual and monolingual musicians and non-musicians switched between tasks or accomplished more than one at once.  These were apparently standard psychological tests, with task switching involving tracking numbers on a computer screen, and dual-tasking involving tracking a white dot while looking at flashing letters, while being asked to note when an X appears.

Results demonstrated reduced global and local switch costs in musicians compared with non-musicians, suggesting that musical training can contribute to increased efficiency in the ability to shift flexibly between mental sets.... These findings demonstrate that long-term musical training is associated with improvements in task switching and dual-task performance.

The researchers point out that there can be 'far transfer effects' of training or experience on cognition. This is a well-studied area of psychology, and it's known that many hours of things like physical exercise or video-gaming can affect how we think, or remember, and so forth.  So, that something as complex as musical training might affect other mental skills isn't a surprise.

And, it has long been known that longterm musical training has effects on brain structure, including on sensorimotor and auditory areas, but on grey matter as well (references here).  And, London taxi drivers are known to have larger hippocampi, related to spatial navigation, than London bus drivers who spend as much time driving.  Multilinguists have denser grey matter in brain areas related to language and communication than do monolingual people.  And so on.

This is all overwhelming evidence for brain plasticity.  It beats me why anyone would insist that intelligence is an exception, hard-wired, and not at all contingent upon experience.