Spatial Memory and Blindness: The Role of Visual Loss on the Exploration and Memorization of Spatialized Sounds

Abstract

Spatial memory relies on encoding, storing, and retrieval of knowledge about objects' positions in their surrounding environment. Blind people have to rely on sensory modalities other than vision to memorize items that are spatially displaced, however, to date, very little is known about the influence of early visual deprivation on a person's ability to remember and process sound locations. To fill this gap, we tested sighted and congenitally blind adults and adolescents in an audio-spatial memory task inspired by the classical card game "Memory." In this research, subjects (blind, n = 12; sighted, n = 12) had to find pairs among sounds (i.e., animal calls) displaced on an audio-tactile device composed of loudspeakers covered by tactile sensors. To accomplish this task, participants had to remember the spatialized sounds' position and develop a proper mental spatial representation of their locations. The test was divided into two experimental conditions of increasing difficulty dependent on the number of sounds to be remembered (8 vs. 24). Results showed that sighted participants outperformed blind participants in both conditions. Findings were discussed considering the crucial role of visual experience in properly manipulating auditory spatial representations, particularly in relation to the ability to explore complex acoustic configurations.

Keywords: acoustic perception; audio-spatial skills; blindness; development; user-friendly technologies; working memory.

FIGURE 1

ARENA2D at two levels of detail. (A) Presents the device. ARENA2D is a vertical surface (50 × 50 cm) composed of 25 haptic blocks, each with a loudspeaker in the center, arranged in the form of a matrix. (B) Shows a single haptic block in detail. The black hole is the speaker from which the sound is emitted. The blocks are covered by 16 (4 × 4 matrix) tactile sensors (2 × 2 cm²) that register the position of each touch.

FIGURE 2

Grids used in experimental conditions. The two grids differ in the size of the apertures for each auditory item. The apertures on the grids represented in the left column are 10 cm × 10 cm, equal to the haptic block size. The apertures on the grids represented in the right panel are 4 cm × 4 cm. Depicted animals placed inside the squares, refer to the position of the animal calls in each grid (images downloaded from a royalty-free website, https://publicdomainvectors.org/). The black dot at the center indicates the speaker emitting feedback sounds.

FIGURE 3

Score. Data are presented as mean and standard error for each group. The white circles on the bars represent the individual data. The Score reached by the participants was lower in the 4-pair condition and the sighted outperformed the blind group in both experimental conditions. * indicates p < 0.05, ** indicates p < 0.01, *** indicates p < 0.001.

FIGURE 4

Number of Attempts. Data are presented as mean and standard error for each group. The white circles on the bars represent the individual data. Even though both groups needed more attempts to end the task in the 4-pair compared to the 12-pair conditions, the sighted group needed fewer attempts to pair the items once their locations have been discovered on ARENA2D but only in the second condition. No significant difference between the groups was found in the first condition instead. * indicates p < 0.05, *** indicates p < 0.001.

FIGURE 5

Audio-Anchor. Data are presented as the mean and standard error. The white circles on the bars represent the individual data. The blind group relied more on the use of the Audio-Anchor regardless of the experimental condition. ** indicates p < 0.01.

FIGURE 6

Score, example of calculation. Score is an index that decreases when participants press a panel they have previously chosen. When two blocks are touched for the first time a Score of 0 is allocated. If they have already touched one or both blocks, the Score decreases by one or two, respectively. When a pair is found the Score increases by ten. In the example, if the starting value were equal to zero, the final Score would be: 0 – 1 – 2 + 10 = 7. Depicted animals were downloaded from a royalty-free images web archive (https://publicdomainvectors.org/).

FIGURE 7

Audio-Anchor, example of calculation. The index equals zero at the beginning of the test. The index increases with more attempts starting with the same haptic block. In the presented example, the final value would be: 0 + 1 + 1 = 2. Depicted animals were downloaded from a royalty-free images web archive (https://publicdomainvectors.org/).