Some people can hold huge amounts of information in their mind and even manipulate it, trying out different ideas, while other people can only hold small amounts. Why do people have the particular capacity they have? How can we investigate these differences between people? It turns out the key to answering these questions is to get people to remember information in only one of their five senses, for example, vision. By doing this we narrow down the field of things to investigate. We can look at the precise brain anatomy related to just that one sense in different people and figure out which parts of their brain allow for greater information capacity. This is exactly what we did in our Cerebral Cortex paper. We found that people with a physically larger visual cortex – the part at the back of the brain that deals with what we see – could hold more temporary information in their memory. This is interesting for a number of reasons because it suggests that the physical parameters of our brains set the limits to what we can do with our minds.
The larger your visual cortex the more visual information it can hold. But the “visual cortex bucket” has to actively hold on to the information. It takes voluntary effort on your behalf to continually hold this information and then use it.
It is worth noting that size is not everything. Many other brain factors can and will influence your mental life and indeed your working memory capacity.
These factors include the degree of internal connections between different brain areas, the level of neural transmitters, the hormones in your body and brain, and of course the amount of stress you are under.
In our study, we found that both the thickness and the surface size of the visual cortex independently predicted how much people could hold in visual working memory. So indirectly at least, it seems that your parents or ancestors might have passed their visual cortex down to you, or at least its size.
It’s all too much and not enough at the same time.
There are words carved in wood, on tree trunks, doors and windowsills.
There is silence as enormous, unframed thought, thought as unframed silence.
Huge undertakings of shape and nerve.
There is pulse and impulse. Clocks in the hall, on the kitchen walls and beside tables.
Verandah swings. Patterns of denial and defeat. Sundials. Shadow.
Open windows. Burls.
There is desire. Lingering desire. Lingering. White trillium and fern.
Dry heat in the poplars. Solitude.
There are voices in the wind. Small stone bowls filled with water
underneath the dripping tap. Birds nests. Clay.
There is turning: to the moon, to myth, to undertone. To the last sentence,
supper, straw. To the finest blade of meaning between what is said and what is not.
There is music. Phrase to phrase, singing to singing. Dolce. Cantabile.
Children on their knees. Knuckles. Fingers. Cycles of a life.
There is mourning. Sleep. The small of the back. Held breath.