Haptic discrimination of different types of pencils during writing

Abstract

Professional artists seem to develop a preference for certain types of pencils and paper (Akyuz 1995). While theaesthetic outcome may be the obvious reason for this preference, haptic feedback may also play a role in selecting media (Prytherch and Jerrard 2001, 2003). This suggestion implies that artists may be sensitive to vibrotactile signals resulting from the interaction between pencil and paper during drawing. Tribological tests showed that H-range leads generate more resistance than B-range pencils when writing on a standard 80 g/m 2 paper. Moreover, a constant stimulus 2IFC procedure showed that Fine Arts students found it easier to discriminate between H-range and HB than B-range and an HB. This suggests that the human haptic system may be sensitive to the vibrotactile signals generated by the differences in resistance resulting from the interaction of leads with the paper's textured surface. Implications for pencil manufacturing and simulations of virtual writing are discussed.

Statement of Relevance: The study assesses the tactile sensitivity of Fine Artists to the physical properties of the interaction between different types of lead and a standard printing paper. The results may help in designing more responsive drawing instruments as well as more realistic virtual drawing interfaces.

Keywords:

• pencil and paper
• psychophysics
• stochastic variations
• vibrotactile sensitivity

Acknowledgements

This work was partly supported by the European Commission under the IMMERSENCE Integrated Project of the Sixth Frame Program (IST-4–027141-IP).

Notes

1. Data were provided by the Chief Chemist of Staedtler, UK.

2. A 2IFC is a special case of the general two-alternative-force (2AFC) procedure, which is widely used to determine the discrimination thresholds (i.e. the minimum intensity difference between two physical stimuli, which is necessary to be perceived as different) of a physical property of an object or event. In principle, depending on the spatiotemporal characteristics of stimulus presentation, the 2AFC procedures can be classified as follows: (i) 2IFC, in which two stimuli are presented at different time intervals (e.g. two visual stimuli presented at the same location in succession); (ii) spatial 2AFC, in which two different stimuli are presented at different location (e.g. two visual stimuli presented at different parts of the visual field); (iii) spatiotemporal 2AFC, in which two different stimuli are presented at different locations at different time intervals (e.g. two visual stimuli presented at different parts of the visual field in succession). The two stimuli have different intensities (e.g. different levels of brightness) and the observer is asked to indicate which stimulus had the higher intensity (e.g. the first is brighter than the second in the case of a 2IFC).