Brown and Strand (2019)

# Brown and Strand (2019) <h4>Integrating incongruent stimuli may rely on alternative mechanism</h4> " whether integrating speech information from (visual and auditory) modalities occurs automatically or requires attentional resources." There are inconsistent evidence in the literature, but no studies assessed this questions by the comparison of congruent versus incongruent trials. Indirect evidence from some behavior and fMRI studies suggested the integrating congruent and incongruent AV may reply on different mechanisms.( Grant and Seitz , 1998; Van Engen et al., 2017; Calvert, Campbell, & Brammer, 2000) <ul> <li>Responses for incongruent stimuli could be non-fusion or fusion.</li> </ul> <h4>Non-fusion vs. fusion responses</h4> "Non-fusion trials could be faster than fusion trials for at least three reasons." 1. "integration may have failed to occur (or occurred to a lesser extent) during non-fusion trials, so a perceptual decision was made quickly without an additional integration stage." 2. "the participant may have closed their eyes or completely ignored the visual signal during non-fusion trials, and therefore the perceptual system effectively only processed the auditory stream" 3. "the percept that arose during fusion trials may not have cleanly fit into a perceptual category, ... so assigning this imperfect representation to a category required additional processing time or resources that exceeded those required for processing non-fusion trials." "fusion trials may be processed more quickly than non-fusion trials for multiple reasons." 1. " In non-fusion trials, participants may have tried to integrate the auditory and visual information, and upon failure to do so, had to resort to processing the auditory input and assigning it to a perceptual category, which required additional time or resources beyond those required for processing trials during which integration successfully occurred " 2. " participants may have noticed the incongruity more often in non-fusion trials, and the recruitment of conflict detection and resolution mechanisms – or simply distraction – slowed responding" 3. "the influence of the visual signal on the non-fusion trials may have been strong enough that the resulting percept, though ultimately classified as a non-fusion, was such a poor category exemplar that assigning it to an phoneme category slowed responses " <h4>Closed-set vs. open-set tasks</h4> " responses to the incongruent stimuli may be particularly slowed in the closed-set condition (which requires the additional task of assigning the percept to a discrete perceptual category and determining category goodness) compared to the open-set condition, in which participants are free to produce whatever they perceived." " responses to congruent stimuli may be speeded in closed-set compared to open-set tasks; if congruent AV stimuli provide a strong match for a phoneme category that has been defined by a response key, this may facilitate recognition of the spoken phoneme and speed responses. Slower responses to incongruent responses may be confounded by 1. " incongruent trials during which participants fail to perceive a McGurk fusion," 2. " task constraints in which participants are required to make closed-set categorizations rather than open-set identifications" <h4>EXP1 goals</h4> "... to use an open-set task to determine whether incongruent stimuli that result in McGurk fusions are processed more slowly than congruent stimuli." RTMcGurk fusions > RTCongruent 1. "If we replicate prior research when we collapse across incongruent response types but not when we analyze only fusion responses, this would suggest that the previously reported response time differences between congruent and incongruent trials are driven by the incongruent trials in which participants fail to experience the McGurk effect." 2. "we compared response times to fusion and non-fusion responses to determine whether these two response types are processed differently." 3. Exploratory analysis on fusion vs. non-fusion response speed <h4>EXP2 goals</h4> in dual-task, if "integrating incongruent AV speech is more attentionally demanding than integrating congruent speech." <ul> <li>For second task responses: RTIncongruent > RTCongruent</li> </ul> Reason: ", slower response times to the secondary task reflect additional attentional costs." because "... humans possess a limited pool of cognitive resources (Kahneman, 1973; Pashler, 1994), so as the primary task becomes more difficult, fewer resources are available to quickly and accurately complete the secondary task" hypothesis: "integrating incongruent stimuli requires more cognitive resources than integrating congruent stimuli." ###### tags: `EXPPSY_Book`