Cognitive Daily reports nearly every day on fascinating peer-reviewed developments in cognition from the most respected scientists in the field.
Inspired by this post, we've decided to devote a week to the analysis of studies from the history of psychology.
Today's post discusses a small fraction of the work done by Hermann Ebbinghaus, a pioneer in the study of memory. Ebbinghaus spent two excruciating year-long periods (1879-80 and 1883-84) painstakingly studying the limits of human memory, using just one experimental participant -- himself.
Ebbinghaus recognized early on that memories were inextricably bound up in their content. It's a very different thing to memorize a poem and an essay, even if the two are the identical length. Memory for visual images is different from memory for sounds, especially musical sounds. He realized that while we can have a song running through our heads in almost the identical form of the original arrangement, our visual recollections are much less precise. So with memory taking so many different forms, and even varying between individuals, where can one begin its study?
Ebbinghaus decided that the best way to start was to simply invent completely new things to remember, so that context could be removed as much as possible from the equation. He created over 2,000 nonsense syllables formed by using 19 consonants for the starting sound, 11 vowel sounds for the middle sound, and 11 consonants for the ending sound (bef, lak, rüch, and so on). As a German speaker, these represented most of the sounds that he could readily produce.
These syllables were arranged randomly into series of varying lengths. Ebbinghaus then attempted to memorize each series, maintaining his pace using a metronome so that he said each syllable in exactly 0.4 seconds. In this way he could precisely time how long it took to memorize each series of syllables.
To track how many times he repeated each series before he had it memorized, he used a set of beads on a string. As you might expect, the longer the series, the longer it took to memorize:
As the number of syllables increased, so did the number of times he had to recite the series before he had it down cold.
But Ebbinghaus noticed something else as he recited his random syllables. The more syllables in the series, try as he might to match the pace set by his metronome, the slower he was able to recite the syllables. Even though he gave himself a strict rhythm to match, something about the structure of memory made recall more difficult, the longer the phrase he needed to recall:
What's notable about Ebbinghaus's study isn't so much the conclusions he draws from it, but the fact that he's the first person to attempt a systematic, experimental study of memory. He actually devised his own system of accounting for error (anticipating standard deviation).
Modern critics of Ebbinghaus might say that entirely divorcing the study of memory from context is pointless -- in the real world, we do remember things in context -- but nonetheless, it's fascinating to see this very early attempt to explore a very complicated phenomenon.
Ebbinghaus, H. (1964). Our knowledge concerning memory. the Method of Investigation. In H.A. Ruger and C.E. Bussenius (translators) Memory: A Contribution to Experimental Psychology. New York: Dover. (Original work published 1885).
Brain & Behavior
Comments
Thanks for the great post. I hope you continue this series past this week.
Posted by: Gordon Woirley | May 27, 2008 9:03 PM
Very interesting. Were any of his studies replicated with larger sample sizes? I don't know about back then, but now an N of 1 just don't cut the mustard.
Posted by: Jordan Horowitz | May 27, 2008 10:20 PM
Interesting! Ebbinghaus was mentioned in a Wired article I read a week or two ago. This is a great follow up.
Posted by: james | May 28, 2008 4:15 AM
Jordan,
Actually the case study continues to be a valuable method in psychology. And for certain disciplines, very low numbers of participants can generate excellent results. Remember that the human genome was first mapped for just one individual. There are some aspects of being human that are shared by everyone.
Posted by: Dave Munger | May 28, 2008 8:15 AM
Thanks for the interesting week! Related to the study of memory from a historical context, I've enjoyed "In Search of Memory" by Eric Kandel.
Posted by: Dan | May 29, 2008 11:22 AM