The Effects of Stimulus Variability in Natural Visual Scenes
Trial Snapshot
- Phase
- Not Applicable
- Status
- Completed
- Sponsor
- University of Pennsylvania
- Enrollment
- 19
- Locations
- 1
- Primary Endpoint
- Psychophysical Measurements of Horizontal Discrimination Threshold
Study Overview
Brief Summary
The natural visual environment is complex and rich with different stimuli and features. The visual system must constantly extract behaviorally relevant visual information from an abundance of irrelevant information in the visual scene. To complicate matters further, the visual feature or stimulus that is most relevant at any given moment can change quickly and frequently in realistic visual environments. The mechanisms by which task-relevant information guides perceptual behavior are not fully understood.
In this study, psychophysical experiments will be used to measure participants' ability to discriminate the horizontal position of a central object within a complex, natural visual scene, as well as to measure how that ability is affected by within-trial variability in the features of background objects in the scene.
The goal of this study is to investigate the overarching prediction that the visual system extracts task-relevant information in a manner that reflects realistically complex visual environments in which the stimuli change quickly and frequently. Specifically, this study will test the hypothesis that task-irrelevant variability in the scene affects participants' ability to discriminate the visual feature that is relevant to the task at hand.
Detailed Description
Background
The natural visual environment is often complex, with a single visual scene containing a wide variety of stimuli. These stimuli can change quickly and frequently. To further complicate matters, the behavioral relevance of any particular stimulus or visual feature can also change at any given moment. Visual perception in realistically complex visual environments requires the constant extraction of task-relevant stimulus information from an abundance of irrelevant information. Understanding how task-relevant information is used to guide behavior in the context of constantly changing, feature-rich visual environments is a key component of understanding perception. This may be particularly true if the visual system is evolutionarily optimized to perform in realistically complex environments in which the behaviorally relevant stimulus or feature can change quickly and frequently.
The goal of this study is to investigate the overarching prediction that the visual system is optimized to extract visual information in a generalized manner that is flexible to the wide variety of constantly changing visual features encountered in natural environments. Specifically, this study will test the hypothesis that, in the context of realistically complex natural scenes, task-irrelevant visual feature variability negatively affects participants' ability to discriminate the visual feature that is relevant to the task at hand.
Methods
Participants
Study Design
- Study Type
- Interventional
- Allocation
- Na
- Intervention Model
- Single Group
- Primary Purpose
- Basic Science
- Masking
- None
Eligibility Criteria
- Ages
- 18 Years to — (Adult, Older Adult)
- Sex
- All
- Accepts Healthy Volunteers
- Yes
Inclusion Criteria
- •Normal visual acuity
- •Capable of giving informed consent
- •Fully vaccinated against COVID-19
Exclusion Criteria
- •Known color deficiencies
- •Diagnosis of retinal disease or inherited retinal disease from family history
- •A psychophysical threshold for horizontal position discrimination that is greater than 0.6 degrees of visual angle (to be determined during the first experimental session)
Arms & Interventions
Healthy participants
Participants will be excluded prior to the experiment if their best-corrected visual acuity is worse than 20/40 in either eye or if they make any errors on the Ishihara plate test.
For enrolled participants, their threshold for horizontal position discrimination will be calculated based on their performance on the experimental task during their first session. Participants will be excluded after the conclusion of their first session if their horizontal position discrimination threshold in the control condition is higher than a maximum value of 0.6 degrees of visual angle, and participants excluded at this point will not participate in any further experimental sessions.
Intervention: Psychophysical task (Behavioral)
Outcomes
Primary Outcomes
Psychophysical Measurements of Horizontal Discrimination Threshold
Time Frame: Approximately 3 weeks
A psychophysical task will be used to measure participants' ability to discriminate the horizontal position of the central object that is presented within the context of background objects in a natural visual scene. The task will be a two-interval forced choice task that presents one stimulus per interval. The task will be to determine whether, compared to the central object presented in the first interval, the central object presented in the second interval is to the left or to the right. The horizontal discrimination threshold is reported below as a function of noise in the stimulus. The horizontal discrimination threshold is defined as the minimum distance in which two stimuli can be recognized as spatially separate in the horizontal plane. The lower the horizontal discrimination threshold the smaller the difference between two stimuli in the horizontal direction to be perceived as distinct.
Secondary Outcomes
No secondary outcomes reported