from molecules to mind
NeurophilosophyKeith R Laws
The term ‘Rashomon effect’ is often used by psychologists in situations where observers give different accounts of the same event,and describes the effect of subjective perceptions on recollection. The phenomenon is named after a 1950 film by the great Japanese director Akira Kurosawa. It was with Rashōmon that Western cinema-goers discovered both Kurosawa and Japanese film in general – the film won the Golden Lion at the Venice Film Festival in 1951, as well as the Academy Award for Best Foreign Language film the following year.
Rashōmon is an adaptation of two short stories by Akutagawa Ryunosuke. Set in the 12th century, the film depicts the trial of a notorious bandit called Tajomaru (played by Kurosawa’s frequent collaborator Toshirô Mifune), who is alleged to have raped a woman and killed her samurai husband. In flashbacks, the incident is recalled by four different witnesses – a woodcutter, a priest, the perpetrator and, via a medium, the murder victim. Each of the testimonies is equally plausible, yet all four are in mutual contradiction with each other.
The film is an examinantion of human nature and the nature of reality. It compels the viewer to seek the truth. Each testimony is influenced by the intentions, experiences and self-perceptions of the witness. They all tell their own ‘truth’, but it is distorted by their past and by their future. Under Kurosawa’s masterful direction, the characters start off happy in the knowledge that they know exactly what happened between the samaurai, his wife and the bandit. One by one, each character begins to doubt their own account of the incident. In the end, both the cast and the viewer are left in a state of confusion and bewilderment.
The idea that we do not remember things as they actually happened is usually attributed to Sir Frederick Bartlett (1886-1969), who spent much of his professional career at Cambridge University, where he became head of the psychology department. He describes the process of memory in his classic 1932 book, Remembering: A Study in Experimental and Social Psychology:
Remembering is not a completely independent function, entirely distinct from perceiving, imaging, or even from constructive thinking, but it has intimate relations with them all…One’s memory of an event reflects a blend of information contained in specific traces encoded at the time it occurred, plus inferences based on knowledge, expectations, beliefs, and attitudes derived from other sources.
According to Bartlett, memories are organized within the historical and cultural frameworks (which Bartlett called ‘schemata’) of the individual, and the process of remembering involves the retrieval of information which has been unknowingly altered in order that it is compatible with pre-existing knowledge.
Bartlett’s ideas about how memory works came to him during a game of Chinese whispers, in which a short story is relayed through a chain of people, each of whom makes minor retrieval errors, such that the final retelling may be completely different from the original. One of his experiments involved asking subjects to read a Native American folk story called The War of the Ghosts, and then recall it several times, sometimes up to a year later. He chose it because the cultural context in which it is set was unfamiliar to the participants in his experiments.
Bartlett found that upon recall, the subjects altered the narrative of the story to make it fit in with their existing schemata. Participants omitted information they regarded as irrelevant, changed the emphasis to points they considered to be significant, and rationalized the parts that did not make sense, to make the story more comprehensible to themselves. In other words, memory is reconstructive rather that reproductive.
Although Remembering was largely ignored upon its publication, it is today highly influential. Elizabeth Loftus, a professor of psychology and law at the University of California, Irvine, has devoted her career to studying the reconstructive nature of memory in relation to eyewitness testimony.
Loftus is concerned mainly with how the recollections of eyewitnesses can be deliberately manipulated by misinformation. In extreme cases, this can lead to completely false memories of events that did not take place. One of Loftus’s more famous studies addresses the use of ‘leading’ questions in the courtroom. In the study, students were shown film clips of a car accident, and then asked a question about the accident. Those asked “About how fast were the cars going when they smashed into each other?” gave answers which averaged about 39 mph, whereas those asked “About how fast were the cars going when they contacted each other?” gave answers with an average speed of 32 mph.
Loftus’s research, like that of Bartlett’s, shows that our memories are quite often not as accurate as we would like to think they are. The knowledge that memory is to some extent confabulation has very serious implications for the use in the courtroom of eyewitness testimonies, because if eyewitness testimonies can be unreliable, then the validity of criminal convictions based upon them is open to question.
As well as confabulating the past, the brain also envisages events that have not yet occurred. The process of anticipating oneself attending a future event probably involves drawing on past experiences to generate a ‘simulation’ of the future event. In an essay in this week’s issue of Nature, Daniel Schacter argues that this ‘episodic-future’ thinking is entirely dependent on reconstructive memory:
…future events are not exact replicas of past events, and a memory system that simply stored rote records would not be well-suited to simulating future events. A system built according to constructive principles may be a better tool for the job: it can draw on the elements and gist of the past, and extract, recombine and reassemble them into imaginary events that never occurred in that exact form. Such a system will occasionally produce memory errors, but it also provides considerable flexibility.
Most of the evidence that reconstructive memory may be essential for envisioning future events comes from amnesic patients who also have difficulties picturing themselves in the future, and now there is also some experimental evidence. For example, in a paper published in advance on the Proceedings of the National Academy of Sciences website earlier this week, Szpunar et al describe functional neuroimaging studies which show that some of the brain regions that are activated when recalling a personal memory – the posterior cingulate gyrus, parahippocampal gyrus and left occipital lobe – are also active when thinking about a future event.
Related posts:
References:
Hassabis, et al. (2007). Patients with hippocampal amnesia cannot imagine new experiences. PNAS DOI: 10.1073/pnas.0610561104
Szpunar, K. K., et al. (2007). Neural substrates of envisioning the future. PNAS DOI: 10.1073/pnas.0610082104.
Schacter, D. L. & Addis, D. R. (2007). Constructive memory: The ghosts of past and future. Nature 445: 27-29.
Loftus, E. F. (2003). Our chaneable memories: legal and practical implications. Nature Rev. Neurosci. 4: 231-234.
Loftus, E. F. (1975). Leading questions and the eyewitness report. Cognitive Psychology 7: 560-572.
No comments:
Post a Comment