Differences between early-blind, late-blind, and blindfolded-sighted people in haptic spatial-configuration learning and resulting memory traces

Haptic recognition of two-dimensional raised-line patterns by early-blind, late-blind, and blindfolded sighted adults

We investigated the role of visual experience and visual imagery in the processing of two-dimensional (2-D) tactile patterns. The performance of early-blind (EB), late-blind (LB), and blindfolded sighted (S) adults in the recognition of 2-D raised-line patterns was compared. We also examined whether recognition of 2-D tactile patterns depends on the type of memory strategy (eg spatial, visuo-spatial, verbal, and kinesthetic) used by EB, LB, and S participants to perform the task. Significant between-group differences in the recognition performance have not been found despite significant between-group differences in self-reported memory strategies. Recognition performance does not vary significantly with the strategy, but correlates positively with visuo-spatial imagery abilities in the S participants. These findings may be taken to suggest that the difficulties some blind people experience with tactile pictures are not due to difficulties in processing 2-D tactile patterns.

Human Echolocation: Blind and Sighted Persons' Ability to Detect Sounds Recorded in the Presence of a Reflecting Object

Research suggests that blind people are superior to sighted in echolocation, but systematic psychoacoustic studies on environmental conditions such as distance to objects, signal duration, and reverberation are lacking. Therefore, two experiments were conducted. Noise bursts of 5, 50, or 500 ms were reproduced by a loudspeaker on an artificial manikin in an ordinary room and in an anechoic chamber. The manikin recorded the sounds binaurally in the presence and absence of a reflecting 1.5-mm thick aluminium disk, 0.5 m in diameter, placed in front, at distances of 0.5 to 5 m. These recordings were later presented to ten visually handicapped and ten sighted people, 30–62 years old, using a 2AFC paradigm with feedback. The task was to detect which of two sounds that contained the reflecting object. The blind performed better than the sighted participants. All performed well with the object at < 2 m distance. Detection increased with longer signal durations. Performance was slightly better in the ordinary room than in the anechoic chamber. A supplementary experiment on the two best blind persons showed that their superior performance at distances > 2 m was not by chance. Detection thresholds showed that blind participants could detect the object at longer distances in the conference room than in the anechoic chamber, when using the longer-duration sounds and also as compared to the sighted people. Audiometric tests suggest that equal hearing in both ears is important for echolocation. Possible echolocation mechanisms are discussed.

What is the link between language and spatial images? Behavioral and neural findings in blind and sighted individuals

In order to find objects or places in the world, multiple sources of information, such as visual input, auditory input and asking for directions, can help you. These different sources of information can be converged into a spatial image, which represents configurational characteristics of the world. This paper discusses the findings on the nature of spatial images and the role of spatial language in generating these spatial images in both blind and sighted individuals. Congenitally blind individuals have never experienced visual input, yet they are able to perform several tasks traditionally associated with spatial imagery, such as mental scanning, mental pathway completions and mental clock time comparison, though perhaps not always in a similar manner as sighted. Therefore, they offer invaluable insights into the exact nature of spatial images. We will argue that spatial imagery exceeds the input from different input modalities to form an abstract mental representation while maintaining connections with the input modalities. This suggests that the nature of spatial images is supramodal, which can explain functional equivalent results from verbal and perceptual inputs for spatial situations and subtle to moderate behavioral differences between the blind and sighted.

Memory for an imagined pathway and strategy effects in sighted and in totally congenitally blind individuals

The literature reports mixed results on the imagery abilities of the blind, at times showing a difference between sighted and blind individuals and at other times similarities. However, the possibility that the results are due to different strategies spontaneously used in performing the imagery tasks has never been systematically studied. A large group of 30 totally congenitally blind (TCB) individuals and a group of 30 sighted individuals matched for gender age and schooling were presented with a mental pathway task on a complex two-dimensional (5 x 5) matrix. After administering the task, participants were interviewed in order to establish the strategy they used. Results showed that both sighted and TCB may use a spatial mental imagery, a verbal or a mixed strategy in carrying out the task. Differences between the groups emerged only when last location and then entire pathway had to be remembered rather than just the last position, and were clearly affected by the type of strategy. Specifically, TCB performed more poorly than the sighted individuals when they used a spatial mental imagery strategy, whereas the two groups had a similar performance with a verbal strategy.

Keep an eye on your hands: on the role of visual mechanisms in processing of haptic space

The present paper reviews research on a haptic orientation processing. Central is a task in which a test bar has to be set parallel to a reference bar at another location. Introducing a delay between inspecting the reference bar and setting the test bar leads to a surprising improvement. Moreover, offering visual background information also elevates performance. Interestingly, (congenitally) blind individuals do not or to a weaker extent show the improvement with time, while in parallel to this, they appear to benefit less from spatial imagery processing. Together this strongly points to an important role for visual processing mechanisms in the perception of haptic inputs.