Canonical Size in Haptic Drawings

Drawing as a tool for investigating the nature of imagery representations of blind people: The case of the canonical size phenomenon

Several studies have shown that blind people, including those with congenital blindness, can use raised-line drawings, both for "reading" tactile graphics and for drawing unassisted. However, research on drawings produced by blind people has mainly been qualitative. The current experimental study was designed to investigate the under-researched issue of the size of drawings created by people with blindness. Participants (N = 59) varied in their visual status. Adventitiously blind people had previous visual experience and might use visual representations (e.g., when visualising objects in imagery/working memory). Congenitally blind people did not have any visual experience. The participant's task was to draw from memory common objects that vary in size in the real world. The findings revealed that both groups of participants produced larger drawings of objects that have larger actual sizes. This means that the size of familiar objects is a property of blind people's mental representations, regardless of their visual status. Our research also sheds light on the nature of the phenomenon of canonical size. Since we have found the canonical size effect in a group of people who are blind from birth, the assumption of the visual nature of this phenomenon - caused by the ocular-centric biases present in studies on drawing performance - should be revised.

Effects of scaling direction on adults' spatial scaling in different perceptual domains

The current study investigated adults' strategies of spatial scaling from memory in three perceptual conditions (visual, haptic, and visuo-haptic) when scaling up and down. Following previous research, we predicted the usage of mental transformation strategies. In all conditions, participants (N = 90, aged 19-28 years) were presented with tactile, colored graphics which allowed to visually and haptically explore spatial information. Participants were first asked to encode a map including a target. Then, they were instructed to place a response object at the same place on an empty, constant-sized referent space. Maps had five different sizes resulting in five scaling factors (3:1, 2:1, 1:1, 1:2, 1:3). This manipulation also allowed assessing potentially symmetric effects of scaling direction on adults' responses. Response times and absolute errors served as dependent variables. In line with our hypotheses, the changes in these dependent variables were best explained by a quadratic function which suggests the usage of mental transformation strategies for spatial scaling. There were no differences between perceptual conditions concerning the influence of scaling factor on dependent variables. Results revealed symmetric effects of scaling direction on participants' accuracy whereas there were small differences for response times. Our findings highlight the usage of mental transformation strategies in adults' spatial scaling, irrespective of perceptual modality and scaling direction.

Size and Quality of Drawings Made by Adults Under Visual and Haptic Control

The aim of this study was twofold. First, our objective was to test the influence of an object’s actual size (size rank) on the drawn size of the depicted object. We tested the canonical size effect (i.e., drawing objects larger in the physical world as larger) in four drawing conditions — two perceptual conditions (blindfolded or sighted) crossed with two materials (paper or special foil for producing embossed drawings). Second, we investigated whether drawing quality (we analysed both the local and global criteria of quality) depends on drawing conditions. We predicted that drawing quality, unlike drawing size, would vary according to drawing conditions — namely, being higher when foil than paper was used for drawing production in the blindfolded condition. We tested these hypotheses with young adults who repeatedly drew eight different familiar objects (differentiated by size in the real world) in four drawing conditions. As expected, drawn size increased linearly with increasing size rank, whatever the drawing condition, thus replicating the canonical size effect and showing that this effect was not dependent on drawing conditions. In line with our hypothesis, in the blindfolded condition drawing quality was better when foil rather than paper was used, suggesting a benefit from haptic feedback on the trace produced. Besides, the quality of drawings produced was still higher in the sighted than the blindfolded condition. In conclusion, canonical size is present under different drawing conditions regardless of whether sight is involved or not, while perceptual control increases drawing quality in adults.