It’s the night before your big exam. There you are, hunched over your books, highlighter in hand, caffeine in your bloodstream, flooding your short term memory with as much as you can. You continue doing so even as you wait to be called into the exam hall. You try and remember as much as you can. The next day, as the adrenaline leaves your system and you can finally get your life back you realise you remember very little about what you covered in those final, intense sessions of revision. The following day you remember even less. Eventually, despite having forced yourself to remember all those final bits of knowledge, you realise you remember nothing of it. You’ve passed your exam yet you have actually learnt nothing. We’re all guilty of the learn and burn approach of cramming. Yet we are all living, breathing proof it doesn’t work. This is the story of Hermann Ebbinghaus, the forgetting curve and how interleaving our learning can prevent the loss of knowledge.
Hermann Ebbinghaus (1850 – 1909) was a German psychologist. Contrary to the scholarly fashion of the time he was interesting in studying memory using himself as a test subject. He tried to memorise a collection of nonsense words and plotted how many he could remember a week or so later. He published his work in 1885 as Über das Gedächtnis (later translated into English as Memory: A Contribution to Experimental Psychology). He charted how poor recall was following an isolated learning event was without frequent calls to draw on that knowledge. The more frequently he recalled the nonsense words the longer he could remember them. This is the forgetting curve.
Ebbinghaus gave the process a formula and hypothesised several contributing factors to the ability to recall knowledge: how complex the subject was, how it linked to previous learning, and personal factors such as sleep and stress. Time is unlikely to be the sole factor but the forgetting curve demonstrates a remarkable loss of learning unless that subject is regularly reviewed as shown below.
However, through repeated reviews of the learning material (the stars) we can shift the learning curve and improve retention of knowledge. This shows how it is impossible to cover everything in a talk. Your audience won’t retain it. It shows the importance of frequent recall rather than a single isolated event.