Blindwalking to replicate an instructed distance requires various sensory signals. Recent evidence in movement science across many organisms suggests that multifractal organization of connective tissue supports the use of these signals. Multifractal structure is a multiplicity of power laws defining distribution of proportion across many time scales that helps predict judgments of the objects' length. Present work tests whether the multifractal structure in postural accelerometry during blindwalking predicts blindwalking distance replications. Ten undergraduate student participants each completed 20 trials of distance-perception each comprising two laps. On each Lap 1, experimenters led participants to walk on any of five prescribed distances, randomly assigning half to walk Lap 1 with eyes open and another half to walked Lap 1 with eyes closed. On Lap 2, all participants walked with eyes closed to replicate instructed distances from Lap 1. We collected postural accelerometry from the torso during each lap. Regression modeling showed that multifractality of postural accelerometry on both Lap 1 and Lap 2 contributed significantly to Lap-2 blindwalking responses. According to this model, more accurate Lap-2 replications of Lap-1 distance came from eyes-closed participants whose posture had comparable multifractality on both laps. Multifractality provides insights into the sequence of exploratory behaviors for blindwalking responses to distance perception.Keywords Perception and action . Haptics . Kinesthesis Distance perception draws on multiple physiological systems. Optical variables inform sighted distance judgments (e.g., Wu, He, & Ooi, 2007), and participants with eyes closed can blindly walk a distance commensurate with distance to that target (Thomson, 1983;Elliott, 1986). Blindwalking participants use haptic information from footfalls and postural corrections to feel their way on "how long" it is to the target (Loomis, Da Silva, Fujita, & Fukusima, 1992;Loomis et al., 1993). Vestibular signals provide self-motion cues (e.g., Etienne & Jeffery, 2004;McNaughton, Battaglia, Jensen, Moser, & Moser, 2006). Blindwalking participants must integrate their visual trace with an efference copy encoding muscular effort together with various vestibular, tactile, and proprioceptive signals (Ivanenko, Grasso, Israel, & Berthoz, 1997).Signal transmissions from footfall to central executive rely on the nesting of connective tissues across various scales weaving muscle, tendon, bone, and nervous tissue together. Of course, the signals travel through neural tracts in humans, but postural adaptations occur faster than neural transmission allows in multicellular organisms much smaller than humans posing shorter neural distances to traverse (e.g., Endlein & Federle, 2013) but also in humans, supporting quiet standing (Marsden, Merton, & Morton, 1983), speech (Kelso, Tuller, Vatikiotis-Bateson, & Fowler, 1984), and hopping (Moritz & Farley, 2004). The connective tissues constitute a hierarchically organized network of s...
Nesting is a major cornerstone in ecological theorizing about visual perception, through both nesting of surface layout in locomotory movements and nesting of visually available surfaces within each other, from focal to peripheral vision. This work sought to probe these nesting relationships by examining the effects of the visual periphery on the strength of interactions among nested time scales in head sway. That is, we tested whether spatial nesting of the focal within peripheral visual fields stimulated nonlinear interactions amid temporal nesting. We examined head sway during 2 variants of the Fitts task, one involving manual pointing by seated participants and another involving walking comfortably with upright standing posture. All participants completed both tasks but were randomly assigned to experience these tasks with or without the visual periphery available. Multifractal analysis of head sway revealed that visual availability of the periphery promoted nonlinear interactions across nested time scales, but this effect depended on how much head sway extended across a plane than more ballistically along a single axis of variability.
Previous literature on self-training dynamic touch suggested that haptic judgments of length following wielding might benefit from new information through participants' own striking actions with the same stimuli. However, the conclusion that this self-training tended towards a veridical outcome of zero discrepancy between actual length and judged length was premature. In this replication, we allowed adult participants (n = 15) to strike on each trial and changed the stimuli in mid-experiment to determine whether striking helped participants build more accurate perceptions of length transferrable from one stimulus scale to another. We predicted that, if selftraining led to better length judgments, the repeated striking would improve judgments and that, in turn, judgments following the switch of stimuli would show a good transfer of what participants had learned. On the other hand, self-training may simply exaggerate inertial properties of stimuli and may be sensitive to sudden changes in the scale of stimuli. Mixedeffect modeling of discrepancies show that striking only accentuated effects of inertial moment, producing exaggerated length judgments. Correlation between perceived length and actual length increased only for participants who experienced a switch in individual stimuli but not stimulus scale. We discuss the implications of these findings for any theoretical relationship between self-organization and veridicality.
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