Monday, June 21, 2010

Brain damage and comprehension of comics

Bihrle, Amy M., Hiram H. Brownell, John A. Powelson, and Howard Gardner. 1986. Comprehension of humorous and nonhumorous materials by left and right brain-damaged patients. Brain and Cognition 5:399-411.

This study compared the narrative comprehension of people with damage to either the right or left hemispheres (RH vs. LH) of their brains (often from strokes or physical damage, like concussions).

They used a "completion task" where they were shown three panels from a comic strip, and were asked to provide either a humorous ending or a non-humorous ending with a choice of panels. The humorous ending was the original strip's final panel. The non-humorous ending was manipulated to have one of four varying degrees of coherency related with the strip:

1) ordinary endings with non-funny events that still made sense
2) endings associated to the strip but non-sequitur, such as featuring water if the strip had water in it
3) totally non-sequiturs that had no relation to the strip and weren't funny
4) humorous endings but that were non-sequitur given the context of the strip

Overall, they found that people with right hemisphere damage made far more errors than Left hemisphere patients. Left hemisphere damaged patients did far better, and several actually hit the ceiling of good performance.

In errors for the task that asked them to provide humorous endings, Right hemisphere patients generally erred by choosing endings that were surprising but not coherent, while left hemisphere patients chose unsurprising but coherent endings. Right hemisphere damaged patients were most drawn to non-sequitur endings of various types, and not to the ordinary ones. Left hemispheric damaged patients showed the opposite results.

However, when asked to provide a non-humorous ending, both types of patients generally chose endings meaningfully associated to the strip but still non-sequitur.

These results are consistent with the poor understanding of verbal narrative and jokes by right hemisphere damaged patients. Overall, they do seem to be sensitive to the formal properties of jokes (such as that an ending should be surprising), but they seem unable to establish coherency between panels.

Monday, June 07, 2010

2D Drawing: comprehending and producing

Scott points to this interesting article about the cognition motivating line-drawings. It makes the claim that people with lazy eyes may have a better ability to draw 2D figures because they have trouble with depth perception to begin with.

Mostly I find this prospect intriguing, though I do somewhat question the assumptions motivating this idea, revealed in this quote:
"Although we experience the world as three-dimensional (thanks to the separation of our two eyes, which produce two different vantage point, and the visual cortex, which reassembles the images into a cohesive landscape), recreating that world in art and film has been challenging."

The implication here is that the capacity to draw is "re-presenting" the perceptual (i.e. 3D) world in 2D form. Rather, I believe the function of drawing is simply to express our concepts in the visual-graphic domain — a modality that is most suited to iconic representations (i.e. "iconic" in the Peircean sense that means "meaning through resemblance"). It's not that we're trying to recreate what we see, but that we're trying to express what's in our heads graphically.

To this end, I think it is important to address a rather large part of the story: the ability to draw in the first place.

More than just the reconversion of seeing into drawings, it's important to consider how we are able to produce line-drawings. One would assume that these capacities would be related — that our perceptual system is adapted to view line-drawings just as much as our minds are built to produce them (I make no claim on which would have evolved first).

I have trouble pinpointing a reason that having impaired depth perception would hinder or advance the ability to draw in circumstances where you're not doing "life drawing." Drawing "from memory" isn't necessarily the pulling up of mental images in place of not having an actual thing to look at. Evidence seems to indicate that drawing pulls from pre-established graphic patterns stored in our minds that are deployed in different ways. When we draw from perception, we route our vision through the schematic information we use to draw. This is why people's life drawing reflects their own "style" — they are those mental patterns. In some ways, learning to draw proficiently with "realistic accuracy" may be the suppression of these schemas.

Further, while the article mentions that monkeys can perceptually recognize what objects are in line-drawings, they cannot produce them. However, babies take minimal amount of time before they start producing them, and without any sort of explicit teaching.

This is a dissociation that seems relevant: if what separates human babies and monkeys is the capacity to produce line -drawings but not to perceive them, it seems like a particularly important part of the story to address in terms of cognition and evolution.


One additional note: anecdotal evidence about pictures of artists with lazy eyes seems like suspect evidence to ground a theory on (and somewhat of population bias). It also mentions Babe Ruth having a lazy eye... does that mean depth perception is a drawback to hitting baseballs? I'd think that'd be very important there!