Colavita visual dominance effect

In 1974, Colavita conducted an experiment, which provided evidence for visual dominance in humans when performing an audiovisual discrimination task. In his experiment, Colavita (1974) presented participants with an auditory (tone) or visual (light) stimulus, to which they were instructed to respond by pressing the ‘tone key’ or ‘light key’ respectively. The results showed that participants had almost equivalent response times for auditory and visual stimuli in unimodal trials. Nevertheless, subsequent experiments have discontinued the use of deception, and continue to show a robust Colavita visual dominance effect. Ngo and her colleagues conducted a similar study where the results were replicated, because their findings showed that under the appropriate conditions and task demand, the Colavita effect can be reversed. Also, Sinnett and his colleagues mention that animals and humans increase their reliance on auditory stimuli in high-arousal situations and when facing potential threats, The findings from this study showed that the Colavita effect continues to occur when stimuli become more complex. == Explanation of visual dominance effect ==

According to Hartcher-O’Brien and colleagues, the Colavita and visual dominance effects can be generally attributed to an imbalance in the ability to access processing resources, namely between vision and other sensory modalities. Failure of a stimulus to access awareness when multiple stimuli are presented at the same time may result in sensory dominance. For decades, there has been a continuous debate regarding whether the Colavita effect occurs at a sensory level or at the level of attention, involving exogenous (involuntary or reflexive) or endogenous (voluntary) attention. Research has found inconclusive results regarding this debate. Posner and colleagues conducted a study to look at the origin and significance of visual dominance. Based on these results, Koppen and his colleagues proposed that the ‘unity effect’ can adequately explain the role of spatial and temporal coincidence between stimuli in modulating the Colavita effect. According to the Unity effect, intersensory bias is greater when the participants unconsciously bind the two sensory events and believe that a single unimodal object is being perceived, rather than two separate events. Semantic Congruency Research has shown that multisensory cues from an object may share certain semantic features, which may contribute to cross-modal binding of sensory information. Sinnett and his colleagues conducted an experiment using meaningful stimuli, and their findings showed that the Colavita effect continued to exist when using complex and meaningful stimuli were used. In addition, Koppen, Alsius and Spence conducted a study which investigated whether the Colavita effect would be modulated by the semantic congruency between the visual and auditory stimulus, using stimuli of similar semantic meaning and complexity. The findings from this study showed that semantic congruency had no effect on the magnitude of the Colavita effect in the experiments, yet it had a significant effect on participants’ performance in the speeded discrimination task. Participants showed a pattern that reflected difficulties with separating the auditory stimulus from the visual stimulus when these stimuli had congruent semantic meaning and were presented simultaneously. For incongruent stimuli, participants had faster response times, which could also be explained by the previously mentioned theory of ‘Failure of Binding’. == No Colavita effect in people with one eye ==

Previous research has shown that people with one eye have enhanced spatial vision, implying that vision in the remaining working eye compensates for the loss of the simultaneous use of both eyes. Furthermore, individuals who have lost the ability to use one sensory system develop an enhanced ability in the use of the remaining senses. It is thought that intact sensory systems may adapt and compensate for the loss of one of the senses. However, little is known about cross-sensory adaption in cases of developmental partial sensory deprivation, such as monocular enucleation, where individuals have one eye surgically removed early in life. In an experiment, Moro and Steeves tested whether participants with one eye showed the Colavita visual dominance effect, and compared their performance to binocular viewers (use of both eyes) and monocular (eye-patched) control participants. In their experiment, Moro and Steeves used a stimulus detection and discrimination task, which had three conditions: unimodal visual targets, unimodal auditory targets, and bimodal (visual and auditory presented together) targets. The binocular and monocular participants both displayed the Colavita visual dominance effect; however the monocular enucleation group did not. Moro and Steeves demonstrated that people with one eye show equivalent auditory and visual processing, compared with binocular and monocular viewing controls, when asked to discriminate between audio, visual, and bimodal stimuli. The lack of visual dominance in the enucleated participants cannot be due to the overall reduction in visual input, as the monocular control group wearing an eye patch performed the same as the binocular normal control group. Moro and Steeves concluded that people with one eye develop an unbiased allocation of sensory resources, which places less emphasis on vision when bimodal stimuli are presented. Although the lack of Colavita effect in people with one eye begins to explore the possibility that a decrease in visual dominance potentially allows for the adaption of other senses, such as audition. ==Visual dominance in other aspects==

Research has shown that vision is the most dominant sense out of the five senses that human beings possess. Vision can dominate over audition in localization judgement, over touch for shape judgement, and over proprioception when trying to determine the position of one's limb in space. Individuals’ perception of auditory stimuli is often influenced by visual stimuli. Visual dominance has been demonstrated in a multisensory illusion called the McGurk effect, where a visual stimulus paired with an incongruent auditory stimulus leads to the misperception of auditory information, resulting in individuals hearing a sound different from the real auditory input. According to Posner and colleagues individuals’ visual system lacks the capacity to properly alert them of possible threats. Therefore, it is possible that visual dominance results from the attention system's attempt to compensate for the visual system's improper alerting capabilities. == Visual dominance in animals ==

Research has shown that vision is also the dominant modality in a number of other animal species; this is thought to be due to the majority of biologically important information being received visually. Visual dominance effects over audition have been reported in cows, rats, and pigeons. For example, Miller conducted an experiment, in which, his findings showed a visual dominance effect for rats. In this experiment, rats were trained to press a lever in response to a visual (light) and to an auditory (tone) stimulus, which could be presented individually or simultaneously. The findings from this experiment showed that rats' response rates were more frequent on the 'light' lever, than on the 'tone' lever, when both stimuli were presented simultaneously. Vision has also been shown to be a dominant modality in pigeons, according to a study by Randich, Klien and LoLordo. Pigeons were trained to perform an auditory-visual discrimination task by depressing two different foot treadles, one when an auditory tone was presented, and another treadle in the presence of a red light. The results from this experiment showed that pigeons demonstrated the Colavita visual dominance effect. When presented with a bimodal (auditory and visual) stimulus, the pigeons always responded on the visual treadle, implying visual dominance. Furthermore, in a subsequent task, Randich and his colleagues delayed the presentation of the visual stimulus relative to the auditory stimulus. Visual treadle responses by pigeons still occurred with a delay interval of less than 500ms, showing that visual dominance still prevailed when visual stimulus onset was delayed. ==The development of visual dominance==

The developmental trajectory for sensory dominance and multisensory interactions still remains to be characterised. There have been many experiments exploring sensory dominance in adult human, animal models and even infants, but there is a dearth of information covering the age range of later childhood and adolescence. While visual dominance prevails in adults, it has been shown that infants and young children demonstrate auditory dominance. Lewkowicz (1988a-1988b) presented 6- and 10-month-olds with audiovisual compounds differing in temporal characteristics (i.e., rate or duration of stimuli presentation) of either the visual or auditory component. Results showed that infants (particularly those aged 6 months) detected temporal changes in the auditory, but not visual modality, indicating auditory dominance in infants. Lewkowicz (1988a) suggests that auditory dominance in early development might be an indication of the ontogenetically asynchronous development of the sensory systems. Further behavioural studies have shown that this auditory dominance persists up to 4 years of age. Nava and Pavani (2013) investigated the development of multisensory interactions in three school aged groups of children (6-7, 9-10, and 10-11 respectively) using the Colavita paradigm, with the aim of directly assessing whether auditory dominance persists beyond 4 years of age and to examine when adult like visual dominance begins to emerge. They found that auditory dominance persists until 6 years of age, and that the transition toward visual dominance starts at school age. In particular, Experiment 1 showed that children aged 6 to 7 years do not exhibit a Colavita effect, implying auditory dominance. 9- to 10-year-old children and 11- to 12-year-old children exhibited adult like visual dominance of the Colavita effect, suggesting that sensory dominance undergoes a developmental change in late childhood. Nava and Pavani (2013) suggest that visual dominance begins to emerge at the ages of 9 to 10 and is consolidated by 11 to 12 years of age. This pattern of sensory dominance, suggests a gradual change in multisensory perception during development, with the consolidation of adult-like processing of multisensory inputs starting from late childhood, where auditory dominance switches with visual dominance. ==See also==