Combining virtual reality and tactile stimulation to investigate embodied finger-based numerical representations

Abstract

Finger-based representation of numbers is a high-level cognitive strategy to assist numerical and arithmetic processing in children and adults. It is unclear whether this paradigm builds on simple perceptual features or comprises several attributes through embodiment. Here we describe the development and initial testing of an experimental setup to study embodiment during a finger-based numerical task using Virtual Reality (VR) and a low-cost tactile stimulator that is easy to build. Using VR allows us to create new ways to study finger-based numerical representation using a virtual hand that can be manipulated in ways our hand cannot, such as decoupling tactile and visual stimuli. The goal is to present a new methodology that can allow researchers to study embodiment through this new approach, maybe shedding new light on the cognitive strategy behind the finger-based representation of numbers. In this case, a critical methodological requirement is delivering precisely targeted sensory stimuli to specific effectors while simultaneously recording their behavior and engaging the participant in a simulated experience. We tested the device's capability by stimulating users in different experimental configurations. Results indicate that our device delivers reliable tactile stimulation to all fingers of a participant's hand without losing motion tracking quality during an ongoing task. This is reflected by an accuracy of over 95% in participants detecting stimulation of a single finger or multiple fingers in sequential stimulation as indicated by experiments with sixteen participants. We discuss possible application scenarios, explain how to apply our methodology to study the embodiment of finger-based numerical representations and other high-level cognitive functions, and discuss potential further developments of the device based on the data obtained in our testing.

Keywords: cognitive science; embodied cognition; finger counting; numerical cognition; virtual environment; virtual reality.

Figure 1

Basic schematic of the four hardware components and how they interact with the user.

Figure 2

Screen capture of the Virtual Reality experience. The image shows the virtual room the participant is in during the experience. The room has a table, a virtual representation of the participant’s hand (shown in black in the image), and a blackboard that can show different visual stimuli, such as pictures of a real hand (shown in the image) or representations of a virtual hand similar to the participant’s or Arabic digits.

Figure 3

Components design of the Tactile Stimulation Device, using the parts described in Table 1. Each small circuit is composed of one vibration motor (coin-shaped object connected through black and red wires), two resistors, one with 1,000 Ohms (marked with the brown, black, red, and golden lines), and one with 100 Ohms (marked with the brown, black, brown, and golden lines), one Diode (the small black component with a grey line on it), a transistor (the black component marked with an N) and the connecting wires.

Figure 4

Final version of the Tactile Stimulation Device as applied to the hand of a participant.

Figure 5

Experimental loop used in the example experiment.

Figure 6

Flowchart illustrating the evaluations steps. Following the development of the tactile stimulation device, it was validated in three tests on the usability of the device itself. After it proved functionally valid, three empirical experiments tested the participants recognition of finger stimulations, as described in Section “Validation of Equipment.”

Figure 7

Soldered connection.