Bias in Auditory Perception

Our brain accomplishes the remarkable feat of processing a continuous stream of incoming sensory information at an astonishing speed. This is possible through simultaneous bottom-up processing of the incoming stimuli and top-down processing of prior knowledge (Kinchla & Wolfe, 1979). Categorization facilitates recognition and also anticipation of the incoming stimuli (also known as predictive coding, e.g., Rao & Ballard, 1999). Therefore, the presentation of written words facilitates the auditory perception of distorted pronunciation (Sohoglu, Peelle, Carlyon, & Davis, 2012). The skill to correctly categorize depends on relevant experience and memory that has been built over time. Perception thus involves a balance between the sensory stimuli and the stored representations in memory. If a category or a mental image is inaccurately matched with the incoming stimuli, biased perception emerges (see examples later). Bias in perception occurs mostly unconsciously and perhaps incessantly—after all, stimuli are unlikely to form a perfect match with stored memory. Perceptual bias is related to cognitive bias, like gender bias, (unintended) discrimination, and placebo effects. The mechanism is the same, viz. the interference of previously stored impressions, information, and knowledge with newly incoming (perceptual or cognitive) information. Most research on bias takes either a cross-modal or a domain-general (rather than a domain-specific) perspective. A textbook example of cross-modal bias in language is the McGurk effect, in which the auditory presentation of a speech sound [IPA ga] and the simultaneous visual presentation of another sound [ba] lead to a blended perception resulting in [da] (McGurk & MacDonald, 1976). Cross-modal perception has been reported for all sensory modes. For instance, biased gustatory perception may arise as a result of food color (Spence, Levitan, Shankar, & Zampini, 2010). Also, vision is influenced by tactile perception and vice versa, for example, in an experiment in which subjects were presented with simultaneous tactile taps and visual flashes (Bresciani et al., 2005). Domain-general bias occurs when cognitive representations bias the interpretation of sensory stimuli. For example, information about the health consequences of acetone smell biases the reports on how the subjects felt after exposure to the smell of acetone (Dalton, Wysocki, Brody, & Lawley, 1997). This leads us to the direction of bias, which is based on expectations. If memory is activated when processing perceptual stimuli, expectations may arise about the exact nature of those stimuli based on prior knowledge. That is the reason why someone who is informed that the odor of acetone …