Tuesday, April 30, 2013

Kanizsa's Triangle: Illusory Contours and the Inferring of the Perceptual World

Since I said a little bit about the title of the blog, I figure I'd say a bit about the image in the banner as well. It's a "Rubin Vase," a "bi-stable" image (sort of like a necker cube, a duck rabbit, or the "Old Woman-Young Woman") in which our brains alternate which part is the figure, and which part is the ground, so that at times it appears as a vace, and at times it appears as two faces, (usually) without us seeing both at the same time. Now, since I'm lazy, and since it's unlikely anyone's reading this anyway, I'm not going to talk about the Rubin's Vase, because to explain it would require a detailed explanation of figure-ground processing, as well as facial recognition (our brains have special areas just for faces, and it turns out the Rubin Vase activates those areas). That's just too much work. But I included the image in the banner because I dig visual illusions, so instead I'll talk about a (comparatively) simpler one, and maybe someday get to Rubin's.

My thing, my groove you might say, in the study of the mind is all about the ways in which our brains build our world, and how little “we”, by which I mean our conscious selves, have any say in it. At higher, cognitive levels, heuristics and biases, unconscious processing, and “hot” reasoning – that is, affect or emotion-driven reasoning – do the bulk of the work in ways that we're all familiar with (if you don't know what I'm talking about, get into an argument on the internet and watch these biases, “hot” processes, and all the other unconscious ways in which we build the world play out in virtual time). At a lower level, though, visual illusions reveal even more interesting, and perhaps frightening, ways in which our brains build our perceptual world. They show that we don't simply take in reality and represent it as it is out there, independent of us. Instead, we meet it with a bunch of built in assumptions and rules of inference that, when conditions are right, cause us to mis-see things out there.

Monday, April 29, 2013

About the Blog's Title

This blog is going to be (mostly) about cognitive psychology, so I wanted a title that was a nod to something, or someone, important to the field. After a bit of deliberation, I decided Hermann Ebbinghaus was a pretty good candidate, but Ebbinghaus is kind of a weird blog title, so I went with his most famous finding, the forgetting curve. You can easily find short descriptions of Ebbinghaus’ life and work online, but I thought I’d say a little bit about why he’s important. By 1885, when Ebbinghaus published his classic work usually translated into English as Memory: A Contribution to Experimental Psychology (which you can read in its entirety here), the study of the human mind or soul was already a couple millennia old at least, but to that point had primarily been studied via reasoning from introspection (even Wundt, generally considered the father of modern psychology, used an introspective method). For some time, psychophysical phenomena such as vision and audition, had been studied using the methods of natural science, because these phenomena were thought to fall under the purview of biology. Higher-order mental phenomena like memory or reasoning, on the other hand, were, if not of a different metaphysical sort than the biological, at least not amenable to the same methods of investigation. Ebbinghaus (and others) thought otherwise, and he set about to both demonstrate that the scientific method could be applied to cognition, and to learn something about memory in the process. So he says in the preface:
In the realm of mental phenomena, experiment and measurement have hitherto been chiefly limited in application to sense perception and to the time relations of mental processes. By means of the following investigations we have tried to go a step farther into the workings of the mind and to submit to an experimental and quantitative treatment the manifestations of memory.
So using only one experimental subject, himself, Ebbinghaus set about memorizing lists of nonsense syllables and, to determine how memory for familiar and meaningful syllables might differ, six stanzas of Byron’s Don Juan. He explored memory from several different perspectives, looking at how quickly syllables of different length are learned, how his memory for the syllables was affected by how long he studied them (SPOILER: studying them longer makes you remember more for a longer period of time), how repeatedly learning the lists affected memory, and how the order of the syllables influenced memory. The forgetting curve, however, comes from his exploration of the effect of time on retention.

Here’s what he did, in short: he first learned the syllables, or stanzas, until he could repeat them all in order perfectly. Then he’d wait for some period of time and relearn them. He measured his retention by comparing the number of times it took him to relearn the list perfectly to the number of times it had originally taken him to learn it. The fewer times it took him, the more work his retention of the list had saved him, so he called the measure “savings.” If he was able to recall the list perfectly on his first try after the delay, retention was 100%. If it had taken him 10 times to learn the list the first time, and he recalled it in 2 tries the second time, then retention was 80%. If it took him 8 tries, retention was 20%. And so on (the complete numbers are in the table at the top, taken from his book).

The results were pretty simple: between the initial learning and a test of savings a short time later, there was large drop in retention, from the 100% after the list had initially been learned perfectly to 58.2% after just 20 minutes. After that, the reduction in savings became smaller with each interval, so that the difference between savings after 3 days (25.4%) and 6 days (21.1%) was much smaller than the difference between the initial learning and 20 minutes. This pattern gets us this graph (via, who apparently got it from Purdue University):

And that is what the basic Ebbinghaus forgetting curve looks like. It seems simple now, and pretty obvious too, but remember this was produced in a time when quantitatively measuring memory was thought by many to be impossible. This was, however seemingly mundane to us, revolutionary to the psychologist of 1885. Cognitive psychology has come a long way since then (for one, we don’t use ourselves as subjects, and we almost always use more than one), but these are the field’s not so humble beginnings. And so in lieu of naming the blog Ebbinghaus, honoring the discipline’s father with the name of his most famous finding seems appropriate to me.

Sunday, April 28, 2013

Let's see if this takes

So, I've been away from blogging for... a while now, which means that I'm completely out of the habit and this probably won't take, but what the hell, right? Let's see if I can at least post semi-regularly. I'll try, and I mean try, to post something long form(ish) on cognitive science or a related field every Thursday, and the rest of the week will be filled either with nothing or little tid bits that may or may not have anything to do with cognitive science. Now, I'm a procrastinator by nature, so when I say "Thursday," I really mean Thursday, or Friday, or if I'm feeling extra-motivated and under-busy, Wednesday, or maybe even Tuesday of next week. So Thursday it is.