The Forgetting Curve: How useful is it?

In recent years, the phenomenon dubbed the forgetting curve has tweaked the interest of a growing number of teachers and other educationalists motivated by the application of cognitive psychology to learning. Put simply, the forgetting curve states that newly learned information will fade quickly unless returned to regularly. This makes intuitive sense; if I learn a list of words now and am immediately tested on my ability to recall them, I’m bound to get a fair few of them correct. But test me again next week, and chances are I’ll have forgotten most of them, creating the illusion of learning.

The forgetting curve is one of the oldest examples of experimental psychology, dating back to the early psychology laboratories of the late 19th century and the work of Hermann Ebbinghaus.  Ebbinghaus conducted some of the first systematic studies of memory, although in very limited ways. He began investigating memory as early as 1879 and was appointed professor at University of Berlin in 1885 following the publication of his seminal work Memory: A contribution to experimental psychology. He later moved to the university Breslau  (modern day Wroclaw, Poland) where he investigated how children’s mental ability declined during the school day, laying the groundwork for future intelligence testing.  

What Ebbinghaus Did

However, Ebbinghaus is best known for his efforts to prove that higher mental processes could be studied using experimentation, a notion that flew in the face of opinion at the time. To this end he began a series of experiments that would not only support his hypothesis but would also provide us with some of the most important findings on learning and memory. The method he proposed was alarmingly simple – using himself as the only participant he would learn lists of items and calculate how long it took him to forget them. However, he needed something that could be easily memorised but had no prior cognitive associations. In other words, the items needed to be such that he wasn’t able to use previous information to help him remember them. For example, the word dog isn’t just an item we remember, it has additional information attached to it that relates to all the instances of dog – images, experiences and the very idea of a four-legged canine. Ebbinghaus therefore chose to use nonsense syllables (also known as CVCs, or Consonant-Vowel-Consonant trigrams). However, all trigrams required careful consideration as some nonsense syllables might inadvertently have some kind of prior meaning (BOI sounds like boy; DOT is an actual word). Examples of acceptable words might be DAX, BOK or YAT – they can be vocalised, allowing for simple acoustic encoding and, therefore, have maintenance rehearsal properties, but have no meaning. Trigrams remain a popular method of testing memory, specifically because they prevent participants from drawing on information already held in long-term memory. Ebbinghaus noted that the memorised trigrams would fade over time if he made no effort to recall them.

Ecological Validity

So far, so good. But how realistic are these results? Ebbinghaus, of course, used himself as the only participant – today this would have invalidated any results, but we’ll put that criticism to one side for now. A more pressing matter is one of ecological validity.

Ecological validity is a term used to describe the extent to which findings can be generalised to the real world; we have to ask ourselves Is this what happens in classrooms and lecture theatres or is it confined to the carefully controlled artificial environment of the psychology lab? In this respect, we can concentrate our efforts on the use of trigrams because they don’t represent items that people would need to learn in the real-world – they are certainly useful within an experimental environment, but their usefulness is confined to the psychology lab.

Meaning is Important

The British psychologist Frederic Bartlett rejected the Ebbinghaus method because it avoided the complexity of meaning.  Bartlett argued that Ebbinghaus had thrown out the baby with the bathwater by eliminating meaning from his experiments (Baddeley, 2018). Remembering something we have learned involves an interaction between short-term working memory, semantic long-term memory and episodic long-term memory. When we remember something we have learned, we draw on memories that have been stored over time, which is why future learning is dependent on past learning. Not only that, but we use cues to recall this information and many of these will be episodic. When people recall information, they are often also recalling the time and place where the information was initially encountered (what we call context dependent retrieval) and even our internal biological state (state dependent retrieval). 

Bartlett’s approach couldn’t have been more different. He would present participants with complex material (his most influential study of 1932, dubbed the War of the Ghosts, used a story from Native American folklore) and then asked them to recall it at different time points. Unlike Ebbinghaus, Bartlett was less interested in the amount of information recalled and more in the nature of what was remembered. New information is integrated with existing knowledge, leading to both enhanced recall and errors based around effort after meaning. According to Bartlett, the organisation of such knowledge is reflected in a concept he called a schema, a structured mental representation. Unfortunately, the notion of schemas was thought to be too vague at the time and wouldn’t really be fully explored until the advent of cognitive psychology in the 1950s.

No theory is perfect and all experimental findings can be a critiqued at some level. Often researchers approach the same problem from different perspectives (Bartlett and Ebbinghaus are two good examples) and, consequently, their findings will be different. However, the forgetting curve is particularly problematic if we neglect to take into account its shortcomings. Yes, information is lost over time, yet some seems to stick better than others because the new information is being integrated with previous learning. The time taken to forget is therefore dependent on more than just the passing of time and to think of it is such is to neglect these other important factors.   

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