The Forgetting

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The brain consists of a vast number of cells called neurons, connected to each other by synapses. Synapses enable chemicals to be passed from one neuron to another . These chemicals, called neurotransmitters, can either inhibit or stimulate the performance of neurons.

Rubin, David C.; Hinton, Sean; Wenzel, Amy (1999). "The precise time course of retention". Journal of Experimental Psychology: Learning, Memory, and Cognition. 25 (5): 1161–1176. doi: 10.1037/0278-7393.25.5.1161. hdl: 10161/10146.In the short term memory interference can occur in the form of distractions so that we don’t get the chance to process the information properly in the first place. (e.g. someone using a loud drill just outside the door of the classroom.) Key study: Postman (1960) For example, many people say they can”t remember much about their childhood or their school days. But returning to the house in which they spent their childhood or attending a school reunion often provides retrieval cues which trigger a flood of memories. References Ammons RB, Farr RG, Bloch E, Neumann E, Dey M, et al. (1958) Long-term retention of perceptual-motor skills. Journal of Experimental Psychology 55: 318–328. pmid:13539312 Nelson TO (1971) Savings and forgetting from long-term memory. Journal of Verbal Learning and Verbal Behavior 10: 568–576. It is hard to overestimate the importance of Hermann Ebbinghaus' contribution to experimental psychology. Influenced by the work of the German philosopher Herbart, he was the first to carry out a series of rigorous experiments on the shape of forgetting, which he completed in 1880. The experiment itself was preceded by a period in which he tried out a variety of materials and methods. After having tested himself with tones, numbers, and poem stanzas, he decided that none of these served his purposes. Tones were too cumbersome to handle and too difficult to reproduce for him, he did not find digits zero to nine suitable as basic units for the long-running experiments he envisioned, and the poem fragments he tried to learn (from Byron’s Don Juan) were deemed too variable in the meanings they evoked and therefore likely to cause measurement error [ 8] (p. 14–17). He, therefore, introduced nonsense syllables, which had more uniform characteristics than existing words or other verbal material. In his later experiments on learning, however, he did verify his results with the Don Juan verses, confirming both his main results on learning and his intuition that the latter stimuli did indeed yield much more variance in the data [ 9]. Since his introduction of nonsense syllables, a large number of experiments in experimental psychology has been based on highly controlled, artificial stimuli.

Now, imagine a graph where the vertical axis represents how well you remember something, and the horizontal axis represents time. Right after learning, you're at the peak of the graph, but as time goes on, your memory of that information starts to decline, creating a curve that dips downward. Table 2. Time spent learning (session S1) and relearning (session S2) for each list with savings (Q) by Dros.Murre JMJ, Meeter M, Chessa AG (2007) Modeling amnesia: Connectionist and mathematical approaches. In: Wenger MJ, Schuster C, editors. Statistical and Process Models for Neuroscience and Aging. Mahwah, NJ: Lawrence Erlbaum. pp. 119–162. Jenkins JG, Dallenbach KM (1924) Obliviscence during sleep and waking. American Journal of Psychology 35: 605–612. In general, his memory for events before the surgery remains intact, but he does have some memory loss for events which occurred in the two years leading up to surgery. Although proactive and retroactive interference are reliable and robust effects, there are a number of problems with interference theory as an explanation of forgetting.

Brown, John (1958). Some Tests of the Decay Theory of Immediate Memory. Quarterly Journal of Experimental Psychology, 10, 12-21. There is evidence that the consolidation process is impaired if there is damage to the hippocampus (a region of the brain). In 1953, HM had brain surgery to treat his epilepsy, which had become extremely severe. During the learning phase, the subject had a continuous choice to either read or reproduce the syllables. Towards the end of the learning process, occasional attempts were made to produce an entire row by heart. When there was a moment of hesitation during such ‘blind’ reproduction, the rest of the list was read (i.e., not blind) to the end. Blind reproduction always started with the first syllable of a row. Rows were not learned in parts. Each time the 13 th syllable had been reached and the row still contained errors, it was read again from the beginning. After having learned one row and before starting the next one, there was an interval of 15 sec. The interval served as a moment of rest and pause. All of this was aimed at following Ebbinghaus as closely as possible. Each row was thus learned to a 100% correct criterion before moving to learning the next row.Rubin DC, Hinton S, Wenzel AE (1999) The precise time course of retention. Journal of Experimental Psychology: Learning, Memory, and Cognition 25: 1161–1176.

Woźniak, Piotr A.; Gorzelańczyk, Edward J.; Murakowski, Janusz A. (1995). "Two components of long-term memory" (PDF). Acta Neurobiologiae Experimentalis. 55 (4): 301–305. PMID 8713361. Archived (PDF) from the original on 2010-09-20.Hermann Ebbinghaus hypothesized that the speed of forgetting depends on a number of factors such as the difficulty of the learned material (e.g. how meaningful it is), its representation and other physiological factors such as stress and sleep. He further hypothesized that the basal forgetting rate differs little between individuals. He concluded that the difference in performance can be explained by mnemonic representation skills. Rasch B, Born J. About sleep's role in memory. Physiol Rev. 2013;93(2):681-766. doi:10.1152/physrev.00032.2012 Given that we can trace the history of research on the effects of sleep on memory to the 24 hour point of Ebbinghaus' forgetting curve, we think it is interesting to evaluate this data point more formally. If we can establish the jump in the curve more formally, it will make a stronger case that the 'true shape' of the long-term forgetting curve has a jump in at 24 hours (or perhaps right after the subject has slept), although we may not conclude from this that the local increase is due to sleep per se, which would require more research is necessary for that.