Posts tagged visual experience
Articles and news from the latest research reports.
Ear-witness precision: Congenitally blind people have more accurate memories
Distortions and illusions within human memory are well documented in scientific and forensic work and appear to be a basic feature of memory functioning.
Yet several studies suggest that blind individuals, especially those without any visual experience, possess superior verbal and memory skills.
The researchers from the Department of Psychology ran memory tests on groups of congenitally blind people, those with late onset blindness and sighted people, in collaboration with a research assistant at Queen Mary, University of London.
Each participant was asked to listen to a series of word lists and then recall the words they heard. Past research has found that such words lists normally cause people to falsely “remember” words that are related to those heard, but that were never actually experienced. For example hearing ‘chimney’, ‘cigar’, and ‘fire’ can prompt some to produce a false memory of the word ‘smoke’ when asked to remember the list of words.
The researchers found that not only did the congenitally blind participants remember more words but were also less likely to create false memories of the related words. In contrast, the sighted and late blind participants remembered fewer words and were much more likely to falsely remember the related words that were not read to the participants.
Dr Achille Pasqualotto, postdoctoral researcher and first author of the study, said: “We found that congenitally blind participants reported significantly more correct words than both late onset blind and sighted people. Most of the congenitally blind participants avoided unrelated words, therefore congenitally blind participants can store more items and with a higher fidelity.”
Dr Michael Proulx who led the study added: “Our results show that visual experience has a significant negative impact on both the number of items remembered and the accuracy of semantic memory and also demonstrate the importance of adaptive neural plasticity in the congenitally blind brain for enhanced memory retrieval mechanisms.
“There is an old Hebrew proverb that believes the blind were the most trustworthy sources for quotations and that certainly seems true in this case. It will be interesting to see whether congenitally blind individuals would also be better witnesses in forensic studies.”
The researched is from the paper Congenital blindness improves semantic and episodic memory, published in the journal Behavioural Brain Research.
(Source: bath.ac.uk)
New understanding of brain’s early spatial development
Researchers at the University of Bath have uncovered a new understanding of how the brain develops its sense of space by working with blind people.
The researchers from the University’s Department of Psychology found that people who lose their sight later in life use a different method of following directions to those who are born without sight. This means that the brain needs to have a visual experience early on in life in order to build a visual perspective, or frame of reference, to know what is where.
The researchers carried out a study with participants including those who were congenitally blind; those who became blind later in life; and others who were sighted, to learn which methods the different groups used to remember where things are.
The study revealed that people who have been sighted and then become blind use a ‘allocentric’ reference frame, meaning they remember locations as they are positioned relative to one another, and this is the same as sighted people who do this task, even when blindfolded.
In contrast congenitally blind participants preferred an ‘egocentric’ reference frame meaning they first remember a starting point at home and then store a memory of the locations from the home location. Dr Michael Proulx who led the study said the results help us to understand more about the role of a critical period for developmental vision on spatial cognition and brain organisation.
He said: “In our study we were curious as to whether having visual experience during child development was key to creating the structures in the brain to support such an allocentric reference frame. First we found an interesting difference between the congenitally blind and sighted people: although the sighted people preferred the allocentric, reference frame, the congenitally blind participants preferred the self-centred or egocentric reference frame for remembering locations.
“The important piece of the puzzle, however, was whether the late blind people would perform like the congenitally blind, showing that current visual experience matters, or like the sighted, showing the role of early visual experience. The results were clear: the late blind performed the same as the sighted participants. Therefore having the experience of vision early in life lays the groundwork in the brain for the representation of locations in a different reference frame than that found in people who never had visual experience.”
All of the participants of the study were blindfolded and then walked to the locations of objects in a large room. They were later tested on a computer with a virtual pointing task that asked them to remember objects in the room relative to the other object locations.
Dr Proulx and his colleagues are following up this finding with additional research to investigate how additional information, such as the texture or sound of the environment, might influence the frame of reference used.
This would allow for improved maps rendered in Braille or sound to be produced for visually impaired persons to use in public places, such as rail stations, or in new cities.
They are also examining the impact of visual experience on the neural basis for spatial learning and memory by examining how the congenitally blind and late blind brains represent spatial information in the absence of vision.