In the last post I talked a bit about motor adaptation - recalibrating two sensory sources so that the overall percept matches up with the incoming information. Say you're reaching to a target under distorted vision, like wearing goggles with prisms in them that make it look like you're reaching further to the right than you actually are; this is known as a visual perturbation. When you reach forward, the sense of where you are in space (proprioception) sends signals to the brain telling you your arm's gone forward. However, the visual information you receive tells you you've gone right. Some recalibration is in order, and over the course of many reaches you gradually adapt your movements to match the two percepts up.
There are a couple of stages in motor adaptation. The first stage is very cognitive, when you realise something's wrong and you rapidly change your reaches to reduce the perceived error in your movement. The second stage is much less consciously directed, and involves learning to control your arm with the new signals you are receiving from vision and proprioception. When the prism goggles are removed, you experience what is known as a motor aftereffect: you will now be reaching leftwards, the opposite of what appeared to happen when you were originally given the prisms. Over the course of a few trials this aftereffect will decay as the brain shifts back to the old relationship between vision and proprioception.
All this is very interesting (to me at least!) but what does it have to do with music? Well, today's paper by Otmar Bock looks more closely at how the the Mozart effect affects motor systems by studying the influence of music on motor adaptation. The theory goes that if an increased mood can improve cognitive performance, then the first phase of motor adaptation should be facilitated. However, since motor aftereffects are not a conscious cognitive strategy but an unconscious motor recalibration they should not be affected by the change in mood.
To test this idea, Bock split the participants into three groups and played each group either serene, neutral* or sad music at the beginning of and throughout the experiment. Before listening to the music, after listening for a while and at the end of the study, participants indicated their mood by marking a sheet of paper. While listening to the music, the performed a motor adaptation task: they had to move a cursor to an on-screen target while the visual feedback of the cursor was rotated by 60º. They couldn't see their hand while they did this, so their visual and proprioceptive signals gave different information.
As expected, the music participants listened to affected their mood: the 'sad' group reported a lower emotional valence, i.e. more negative emotions, then the 'neutral' group, which reported a lower emotional valence than the 'serene' group. During the task, as generally happens during these adaptation tasks where the goal is visual (and of course vision is more reliable!), participants adapted their movements so as to reduce the visual error. The figure below (Figure 2 in the paper) shows this process for the three separate groups, where light grey shows the 'serene' group, mid grey shows the 'neutral' group and dark grey shows the 'sad' group:
Adaptation error by group
The first three episodes in the figure show the reaching error during normal unrotated trials (the baseline phase), then from episode 4 onwards the cursor is rotated, sending the error up high (the adaptation phase). The error then decreases for all three groups until episode 29, where the rotation is removed again - and now the error is reversed as participants reach the wrong way (the aftereffect phase). What's cool about this figure is that it shows no differences at all for the 'neutral' and 'sad' groups but there is an obvious difference in the 'serene' group: adaptation is faster for this group than the others. Also, when the rotation is removed, the aftereffects show no differences between the three groups.
So it does seem that being in a state of high emotional valence (a good mood) can improve performance on the cognitive stage of motor adaptation - and it seems that 'serene' music can get you there. And interestingly, mood appears to have no effect on the less cognitive aftereffect stage (though see below for my comments on this).
The two main, connected questions I have about these results from a neuroscience point of view are: 1. how does music affect mood? and 2. how does mood affect cognitive performance? A discussion of how music affects the brain is beyond the scope of this post (and my current understanding) but since the brain is a collection of neurons firing together in synchronous patterns it makes sense that this firing can be regulated by coordinated sensory input like music. Perhaps serene music makes the patterns fire more efficiently, and sad music depresses the coordination somewhat. I'm not sure, but if the answer is something like this then I'd like to know more.
There are still a couple of issues with the study though. Here are the data on emotional valence (Figure 1A in the paper):
Emotional valence by group at three different stages
What you can see here is that the emotional valence was the same before (baseline) and after (final) the study, and it's only after listening to the music for a while (initial) that the changes in mood are apparent. Does this mean then that as participants continued with the task that their mood levelled out, perhaps as they concentrated on the task more, regardless of the background music? Could this be the reason for the lack of difference in the aftereffect phase? After all, when a perturbation is removed participants will quickly notice something has changed and I would have thought that the cognitive processes would swing into gear again, like in the beginning of the adaptation phase.
Also, it's worth noting from the above figure that valence is not actually improved by serene music, but appears to decrease for neutral and sad music. So perhaps it is not that serene music makes us better at adapting, but that neutral/sad music makes us worse? There are more questions than answers in these data I feel.
Hmm. This was meant to be a shorter post than the previous one, but I'm not sure it is! Need to work on being concise, I feel...
*I'm not exactly sure what the neutral sound effect was as there's no link, but Bock states in the paper that it is "movie trailer sound 'coffeeshop' from the digital collection Designer Sound FX®"
Bock, O. (2010). Sensorimotor adaptation is influenced by background music Experimental Brain Research, 203 (4), 737-741 DOI: 10.1007/s00221-010-2289-0
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