Age-Related Changes in the Susceptibility to Visual Illusions of Size
As the global population ages, understanding the impact of aging on visual perception becomes increasingly important. This study investigates age-related changes in size perception in adults through three visual illusions: the Ponzo illusion, the Ebbinghaus illusion, and the height-width illusion. Based on a Bayesian model that conceptualizes the aging brain, which suggests an increased reliance on prior knowledge with aging, this study explores the differences in susceptibility to visual illusions among adults of different age groups. To achieve this goal, the study utilized an online visual illusion test tool developed by our lab—the Ben-Gurion University Test for Perceptual Illusions (BTPI).
Source of the Paper
The paper is titled “Age-related changes in the susceptibility to visual illusions of size,” written by Yarden Mazuz, Yoav Kessler, and Tzvi Ganel, and published in Scientific Reports. The authors are affiliated with the Department of Psychology at Ben-Gurion University of the Negev, and the paper was published in 2024.
Research Process
Subjects and Methods
The study sample included participants from three different age groups: young group (20-39 years, 80 participants), middle-aged group (41-59 years, 70 participants), and elderly group (61-85 years, 80 participants). All participants were recruited through the online platform Prolific and had a good track record of participating in previous experiments. Each experiment lasted about 20 minutes, and participants received a compensation of 3.13 euros. The study adhered to the ethical standards of the Helsinki Declaration and was approved by the ethics committee of Ben-Gurion University.
Experimental Procedure
Participants took the BTPI test, which included the Ponzo, Ebbinghaus, and height-width illusions. Each illusion was presented in separate blocks in the order of Ponzo illusion, Ebbinghaus illusion, and height-width illusion. In each block, stimuli were presented in a random order, with each combination repeated 12 times for a total of 144 trials. Participants needed to choose which object appeared larger by pressing a key on the keyboard.
Data Analysis
In the data analysis, trial data with no response within the time limit (3000 milliseconds) were excluded. Then, the proportion of trials in which each participant reported the reference stimulus as larger (or wider) than the standard stimulus was calculated, and necessary functions were fitted. Key extracted indicators included the point of subjective equality (PSE), constant error (CE), just noticeable difference (JND), reaction time (RT), and goodness of fit (GOF). CE indicates the size of the illusion, calculated by subtracting the PSE value, and JND indicates the perceptual resolution of size differences in the context of the illusion.
Experimental Results
The study first observed significant differences in sensitivity to the Ebbinghaus illusion across different age groups, with older adults showing significantly reduced sensitivity to this size-contrast illusion. In contrast, sensitivity to the height-width illusion increased with age. For the Ponzo illusion, there were no significant differences in sensitivity across different age groups. These results indicate that different visual size illusions are mediated by different perceptual mechanisms.
Detailed data are shown in Tables 1 and 2, and statistical analysis results are shown in Table 3. Figure 3 shows the differences in illusion size among the age groups.
Discussion and Conclusion
The study’s results challenge the widely accepted view that “reliance on prior knowledge increases with age.” Instead, the study shows that the impact of aging on visual perception is more complex, reflecting different effects in different perceptual domains and illusions. Specifically:
- Ebbinghaus Illusion: Sensitivity to this illusion systematically decreases with age.
- Height-Width Illusion: Sensitivity increases with age.
- Ponzo Illusion: No significant differences among age groups.
These findings suggest that the impact of aging on visual perception is multifaceted and manifests differently across various perceptual domains and illusions. These results imply that older adults may have an increased reliance on holistic shape perception but a decreased reliance on local contrast effects processing.
The study highlights the need for further exploration of the influences on different shape perception mechanisms to better understand the mechanisms of shape perception changes with age. Additionally, more research is needed to explore the relationship between the point of subjective equality (PSE) and just noticeable difference (JND) in different illusion contexts.
Through this study, scientists have gained a clearer understanding of the differential impact of aging on various visual illusions, providing new perspectives and references for future research on visual perception changes during the aging process. The new tool (BTPI) used in this study and its high reliability also provide a solid experimental foundation for future research.