Attention Focusing On Unimodal Biases Visual-haptic Integration And Combination

Humans use multiple sources of sensory information derived from several different modalities.All these different sources of information have to be efficiently merged to form a coherent and robust percept.Ernst and Bulthoff divide cue combination into two parts that they refer to as "sensory integration" and "sensory combination"."Sensory integration" describes interactions between redundant sensory signals in the same coordinates."Sensory combination" describes interactions between sensory signals that are not redundant and may be in in different coordinate systems.In visual-haptic integration research,Ernst found that Humans integrate visual and haptic information and determine haptic and visual weights in a statistically optimal fashion.Attention mechanism in the multisensory integration and combination is still unclear.Some researchers found that visual-haptic integration need attention resources.However,other researchers found that integration is pre-attentive so that diverting attention away from a sensory modality has no effect on cue weight and visual-haptic integration even promotes selective attention.Our research manipulated attention focusing on unimodal when participants observing visual-haptic stimuli to research effects of attention on visual-haptic integration and combination.Experiment 1 explored the influence of attention on visual-haptic integration using conflicting visual-haptic stimuli.Participants were presented with slightly conflicting visual-haptic stimuli and were instructed to pay more attention to the stimulus on visual modality,haptic modality,or both(as control condition).Then they were asked to match a comparison stimuli in visual modality and one in haptic modality.The results revealed that the size of chosen comparison stimuli was more closer to the visual size in visual attention condition while the result was more closer to the haptic size in haptic attention and control condition.Experiment 2 and experiment 3 explored the influence of attention on visual-haptic combination using discrimination task of spring compliance.Experiment 2 confirmed the validity of the virtual spring and provided appropriate range of compliance of the real comparison springs.In study 3,participants were presented with a standard virtual spring and a comparison real spring in each trial and were required to choose a stiffer one.They were instructed to pay more attention to the real spring on visual modality or haptic modality while observing.The results revealed that the participants overestimated the compliance of real spring in haptic attention condition while the stiffness of real spring felt softer in the visual condition.Those results in study 1 and study 3 indicates that attention plays a role in multisensory integration and combination process.Focusing attention to a certain modality could improve cue weight or utilization ratio of the modality and finally change the percept.