Haptic discrimination of bilateral symmetry in 2-dimensional and 3-dimensional unfamiliar displays

Abstract

In five experiments, we tested the accuracy and sensitivity of the haptic system in detecting bilateral symmetry of raised-line shapes (Experiments 1 and 2) and unfamiliar 3-D objects (Experiments 3-5) under different time constraints and different modes of exploration. Touch was moderately accurate for detecting this property in raised displays. Experiment 1 showed that asymmetric judgments were systematically more accurate than were symmetric judgements with scanning by one finger. Experiments 2 confirmed the results of Experiment 1 but also showed that bimanual exploration facilitated processing of symmetric shapes without improving asymmetric detections. Bimanual exploration of 3-D objects was very accurate and significantly facilitated processing of symmetric objects under different time constraints (Experiment 3). Unimanual exploration did not differ from bimanual exploration (Experiment 4), but restricting hand movements to one enclosure reduced performance significantly (Experiment 5). Spatial reference information, signal detection measures, and hand movements in processing bilateral symmetry by touch are discussed.

Attenuating the haptic horizontal—vertical curvature illusion

“…There could be an even more important influence on the haptic horizontal-vertical curvature illusion, aside from the haptic exploration method. It is clear that bimanual exploration aids haptic judgments of symmetry (Ballesteros et al, 1997). This benefit of bimanual exploration probably derives from allowing the individual to code patterns with respect to the body midline and use the body as a frame of reference (e.g., Millar, 2006;Millar & Al-Attar, 2002).…”

“…It appears likely that the advantage of bimanual exploration accrued from allowing subjects the ability to make use of coding with respect to the body midline and with respect to the body itself (see Ballesteros et al, 1997;the subjects showed a slight overestimation of size (see Figure 6). …”

Symmetry Detection in Visual Impairment: Behavioral Evidence and Neural Correlates

“…A number of studies have investigated symmetry processing in the haptic modality using two-dimensional (2D) line drawings or three-dimensional (3D) objects as stimuli [39][40][41][42][43][44]. Overall, these studies show that although symmetry plays a role in the haptic recognition of 2D and 3D objects, symmetry is less salient for touch than it is for vision, and other stimulus properties, such as texture, may play a greater role for haptic shape discrimination compared to symmetry [43].…”

“…Indeed, the salience of symmetry in the haptic modality seems to be modulated by several different factors. This includes stimulus characteristics, such as material properties (e.g., texture and hardness), pattern complexity, size, dimensionality (2D/3D) and exploratory strategy [39][40][41][42][43]. Regarding exploratory strategies, symmetry detection during haptic exploration is facilitated when two hands are used [39][40][41].…”

“…This includes stimulus characteristics, such as material properties (e.g., texture and hardness), pattern complexity, size, dimensionality (2D/3D) and exploratory strategy [39][40][41][42][43]. Regarding exploratory strategies, symmetry detection during haptic exploration is facilitated when two hands are used [39][40][41]. This advantage is consistent with the reference-frame hypothesis [44], which suggests that bimanual exploration allows participants to relate the position of their hands to their own body midline providing for an effective frame of reference and also for coding the presence of symmetry in external objects (possibly via alignment of the axis of symmetry with the participants' body midline).…”