Analysis
August 6, 2007
Category: Analysis
It would be difficult to come up with a more frequently confused concept in psychology than reinforcement and punishment. In fact, "reinforcement" and "punishment" aren't difficult to understand on their own: Reinforcement simply means any means of increasing or encouraging the designated behavior; punishment is any means of inhibiting or decreasing the designated behavior.
It was only when B.F. Skinner devised the "positive" and "negative" descriptors that he became the bane of college students for generations to come. Rather than "positive" and "negative," things would have been much simpler if he had used the terms "by adding" and "by removing."
The easiest concept to remember is "positive reinforcement." If you want to train a rat to push a lever, you can reward it by offering a food pellet every time the lever is pressed. The rat will learn very quickly to push the lever. This is positive reinforcement, or "reinforcement by adding."
But people quickly become confused by the term "negative reinforcement." It's much easier to understand if you think of it as "reinforcement by removing." If the behavior you want to reinforce is pushing a lever, you can also train the rat by removing something when the lever is pushed. For example you could play an annoying sound, and pushing the lever could stop the sound. The rat will quickly learn to press the lever whenever the sound is played. This is negative reinforcement, or "reinforcement by removing."
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Posted by Dave Munger at 9:52 AM • Comments (17)
June 20, 2007
Category: Analysis
Euro-update 4: Sperm whale perception
Tuscany is about the last place you might think to go to speculate about the visual system of a whale, but when you're spending three weeks relaxing in a secluded villa, you have a lot of reading time. I've been reading Moby-Dick.
Herman Melville describes the sperm whale with almost obsessive detail in the book, from the shape of its tail to the nature of its skin.
In one chapter, devoted to contrasting the head of the right whale and the sperm whale, we find amazing speculation about both the human and sperm whale visual system. Remember, this was published in 1851:
Far back on the side of the head, and low down, near the angle of [a] whale's jaw, if you narrowly search, you will ... see a lashless eye....
Now, from this peculiar sideway position of the whale's eyes, it is plain that he can never see an object which is exactly ahead, no more than he can one exactly astern. In a word, the position of the whale's eyes corresponds to that of a man's ears; and you may fancy, for yourself, how it would fare with you, did you sideways survey objects through your ears. You would find that you could only command some thirty degrees of vision in advance of the straight side-line of sight; and about thirty more behind it. If your bitterest foe were walking straight towards you, with dagger uplifted in broad day, you would not be able to see him, any more than if he were stealing upon you from behind.
It may be that our vision system is so entwined with our nature that it wouldn't be possible to be human and have a vision system like a whale's. Melville latches on to a crucial implication:
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Posted by Dave Munger at 6:26 AM • Comments (12)
April 26, 2007
Category: Analysis
When Shelley Batts wrote up a report on an article about antioxidants in fruits, she never expected to get contacted by the copyright police, but that's exactly what happened. She had reproduced a table and a figure from the article, and got this notice from an editorial assistant at the publisher:
The above article contains copyrighted material in the form of a table and graphs taken from a recently published paper in the Journal of the Science of Food and Agriculture. If these figures are not removed immediately, lawyers from John Wiley & Sons will contact you with further action.
She was appalled, and let the blogosphere know about it in this post. But she also did exactly what the publisher asked: she removed the figure and the table from her blog, replacing them with hand-generated versions she created in Excel. Should she have gone to all that trouble to comply with the publisher's demands? Doesn't the "fair use" doctrine allow reviewers to use excerpts from a work in critical commentary? Unfortunately, the copyright code isn't as clear as it ought to be on this issue. It says that "criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright." That seems clear enough, but here are the considerations the code lists to be used in determining whether a reproduction of a work qualifies:
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Posted by Dave Munger at 8:19 AM • Comments (8)
April 17, 2007
Category: Analysis
Earlier today I wrote a post about optical illusions. I was hoping it would distract me from thinking about the Virginia Tech shootings. It didn't. I began to see connections between the illusions and the tragedy: That sinking feeling that somebody was being shot, that spiral like a gun sight.
The problem is that human brains are connecting machines: we can connect anything to anything else. Trying not to think about the shootings was the worst thing I could do. How should I be handling it? I should be talking about it directly -- preferably face-to-face or over the phone. I did spend some time talking with Greta and with each of my kids about it last night -- and last night, I slept well. But this morning everyone rushed off to school and to work, and I started watching some of the online footage of the shootings. After a while I couldn't think about anything else, so I began to look for distractions. As I should have known, the distractions just weren't distracting enough, and I kept connecting everything back to the grisly deaths in Virginia.
What I'm planning to do is to call my brother to talk about it. I haven't spoken with him for over three months (mostly because I feel guilty about not calling), so it will be great to catch up and share our thoughts about the tragedy. But I can't call now because of time zone differences. In the meantime, I'll have to settle for virtual conversation with my fellow ScienceBloggers, who have written many, many thoughtful posts on the tragic events in Virginia. In case you're in a similar situation, I thought I'd offer a guide to what the ScienceBloggers are saying.
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Posted by Dave Munger at 12:11 PM • Comments (10)
January 18, 2007
Category: Analysis
Last week's post on how sound affects perception of visual events was the most popular post ever on Cognitive Daily, with over 15,000 visits. This was thanks to links from both Fark's technology page and digg.com. Yet commenters on both sites expressed disappointment with the demo. I wasn't especially happy with it either, but then again, I didn't realize that more people would look at that one post than visited the site in all of February last year!
The problem with the movie is that it's showing two conflicting phenomena. Turn your sound down and watch the movie:
Even though the motion of the ball is the same each time, the shadow cues viewers that the ball "rolls" diagonally across the floor of the box first, then "flies" diagonally across the front of the box. Then the same animation is repeated again. On its own, this is an amazing demo.
But adding sound gives it an additional wrinkle. If you watch the movie with the sound turned on, the audio cues sometimes conflict with the shadows, as I described last week: "In the first two examples, the motion of the ball and shadow is consistent with with the sound effects. In the third example, the shadow suggests that the ball is moving along the ground, but the airplane sound effects might suggest a lift-off and landing. In the final example, the tire skidding suggests motion along the ground, but the shadow again suggests flight."
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Posted by Dave Munger at 1:34 PM • Comments (0)
October 24, 2006
Category: Analysis
There was plenty of interest in yesterday's audio-visual illusion. In case you missed it, I'll post it again here:
Play the movie with the sound turned up. If the illusion works, then you'll see a dot flash twice, accompanied by two beeps. But actually the dot only flashes once. Unfortunately, we've had a hard time getting viewers to see the illusion (as of this writing, just over a quarter of those viewing the video claim to see two or more flashes). I have a couple ideas about why people don't seem to see it reliably here on Cognitive Daily, and I'm going to investigate them further on Casual Friday. But for those who do see the illusion, I thought I'd offer a little more explanation about how it works.
What we're talking about here is a cross-modal effect: one perceptual system (in this case, vision) is affected by another (sound). Cross-modal effects are more common than you might think. The visual system, for example, relies on the sensorimotor system to a very large extent. Think about it this way: when you take a video with a camcorder, every little motion of the camera gets translated into a big jitter on your final video. Videos taken from a car window on a bumpy road are practically unwatchable. Yet sitting in the car, you have no problem seeing all the scenery, with no jitters. That's because your visual system takes into account the sensed motion of your body and adapts.
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Posted by Dave Munger at 8:29 AM • Comments (8)
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