Visual capture
In psychology, visual capture is the dominance of vision over other sense modalities in creating a percept. In this process, the visual senses influence the other parts of the somatosensory system, to result in a perceived environment that is not congruent with the actual stimuli. Through this phenomenon, the visual system is able to disregard what other information a different sensory system is conveying, and provide a logical explanation for whatever output the environment provides. Visual capture allows one to interpret the location of sound as well as the sensation of touch without actually relying on those stimuli but rather creating an output that allows the individual to perceive a coherent environment.
One example of visual capture is known as the "ventriloquism effect," which refers to the perception of speech sounds as coming from a direction other than their true direction, due to the influence of visual stimuli from an apparent speaker. Thus, when the ventriloquism illusion occurs, the speaker's voice is visually captured at the location of the dummy's moving mouth.
Another example of visual capture occurs when a sound that would normally be perceived as moving from left to right is heard while a person is viewing a visual stimulus that is moving from right to left; in this case, both sound and stimulus appear to be moving from right to left.
Defining criteria
Theory
When two sensory stimuli are presented simultaneously, vision is capable of dominating and capturing the other. This occurs as visual cues can distract from other sensations, causing the origin of the stimulus to appear as if it is being produced by the visual cue. Therefore, when an individual is in an environment, and multiple stimuli reach the brain at once, there is a hierarchy that vision will guide the rest of the somatosensory cues to be perceived as though they align with the visual experience, despite where their original source may be. Research has found that the visual and auditory reflexive spatial orienting are controlled through a common underlying neural substrate. Furthermore, studies have shown that vision has an effect in cognitive neuroscience, and provides for a significant effect when visually attended to. This dominance is seen again through a visual-haptic task that vision is capable of making better judgements of an object that physically touching it. It has also been determined, that there are certain amounts of visual capture that occur depending on the task, sometimes allowing the visual system to be entirely dominant, while others provide haptic cues to be prominent.Brain regions
The thalamus is a section of the brain responsible for relaying sensory and motor signals to the cerebral cortex. As stimuli pass through the thalamus, there are specific regions dedicated to each sense, and therefore is able to sort out the multiple parts of an environment an individual experiences in a given moment. Two of these regions are specific to vision and hearing respectively, which may be responsible for the order in which sensory information is coded and then perceived within the cerebral cortex.The retina at the back of the eye is what perceives stimuli, allowing them to travel through the occipital tract to the lateral geniculate nucleus within the thalamus. The data is then transmitted to the occipital lobe where the orientation and other recognizable factors are processed.
The LGN is located near the medial geniculate nucleus which is responsible for organizing auditory stimuli after one hears a specific sound. Because these two systems are closely located to each other, research has shown that this might be where vision is responsible for taking over the perception of an environment and resulting in visual capture. As the multiple senses are organized and the response is sent further into the brain for processing, it is possible that the visual cues were recorded stronger, and therefore everything is perceived in a way that all other senses are a function of this visual cue, resulting in a cohesive experience for the individual, driven by the visual system, therefore fitting the definition of visual capture.
Origin of research
This phenomenon was first demonstrated by Frenchman J. Tastevin in 1937, after studying the tactile Aristotle illusion in 1937. This illusion produces the sensation of touching two objects by crossing one’s fingers and then holding a spherical object between them. Visual capture was used to explain how vision could overcome this effect and determine what is actually going on.Attention was again tied to visual cues during an experiment conducted by Michael Posner in 1980. By determining which direction a stimulus will appear with an arrow, response time will increase if the correct direction is attended to. This ability to attend to a specific direction allows the visual system to prove its strength and allow for a faster reaction time. Because of the evidence that vision has on reaction time, it is clear that vision is capable of manipulating the perception an individual has on an environment, and results in what Tastevin considered visual capture. The inclusion of vision in determining where a stimulus will appear increases the efficacy at which a participate will react, proving that vision has a neurological effect on the attentional process. Although a task may be controlled in selecting a box, when vision is skewed to a certain direction by attention, the task becomes easier, and resolves the ambiguity of the scenario.
Examples
Examples in research
A number of studies have demonstrated the visual capture effect. For example, Alais and Burr using the ventriloquist effect, found that vision is capable of taking over auditory senses, specifically with well localized visual stimuli. This means that when the stimuli producing the sound as well as vision are close together, there seems to be a direct relationship formed in the perception of these separate stimuli, that correlate them into the same sensation.Another example of visual capture comes from Ehrsson, Spense, & Passingham who used a rubber hand to prove that vision is capable of determining how other senses react. As participants watched a rubber hand be stroked, their hand was also stroked in a similar fashion, allowing the individual to attribute their own sensation to what they were watching rather than what was happening to their own . Therefore, when the rubber hand was then manipulated, for example hitting it with a hammer, the participant feels an immediate shock and pain as they fear that it is their own hand that is in danger. This serves as evidence that the visual system is capable of not only manipulating where an individual perceives another sense to be coming from, but can actually manipulate how one reacts to an experience as well, given that it is vision that is taking charge.
A study by Remington, Johnston, & Yantis found that attention is involuntarily drawn away from a given task when a visual stimulus interferes. In this study, participants were presented with four boxes; they were told that an image would precede a letter that they were to memorize. The conditions were either to attend to the same box, a different one, all four, or to focus on the center. However, even though they were told to not attend to a certain box, the participant was consistently drawn to the image before the letter in all cases, resulting in a longer response time in all conditions except for the same. The results prove that there is a consistent need for vision to dominate the other senses, and attention is immediately drawn away by it in a controlled setting.
The research in visual capture does not all work in the favor of vision being constantly dominant, as Shams, Kamitani, & Shimojo in 2000 found that visual illusion can be induced by sound in a controlled environment. When a flash of light is accompanied by a series of auditory beeps, the results show that the participant views the flash to be a series of flashes corresponding with the beeps. Because in this experiment hearing seemed to be the dominant sense, it is clear that there is still plenty to be determined about visual capture, although this like the other studies, proves that there is a connection between these two senses when it comes to integrating the perception of an environment.
Everyday examples
An example of visual capture experienced in daily life is known as the “ventriloquism effect”. This is when ventriloquists make their speech appear to be coming from their puppet rather than their own mouths. In this situation, visual capture allows the audio stimuli to be controlled by the vision system and produce a congruent experience that the sound is coming from the puppet.Another popular example of visual capture happens while watching a movie in a theater, and the sound appears to be coming from the actors lips. Although this may seem true, the sound is actually coming from the speakers, often spread out across the theater rather than directly behind wherever the character’s mouth may be.
There is also a phenomenon known that while crossing a street, an individual can hear the sound of an oncoming car. However, when they look to the left the next car is a few blocks away so it is safe to cross. But when they look to the right, there is a car that is passing them that they did not even notice before. This occurs because the individual attributes the sound of oncoming traffic to the first car because they were unaware of the other, closer car. This therefore is an example of visual capture reassigning the audio cue to the incorrect visual cue, resulting in a mistake that could be far more costly than expected.