International Journal of Affective Engineering Vol.12 No.3 pp.375-384 (2013)

ORIGINAL ARTICLE

Visual and Sensory Properties of Texturesthat Appeal to Human Touch
Hikaru NAGANO, Shogo OKAMOTO and Yoji YAMADA
Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya-shi, Aichi 464-8603, Japan
Abstract: Some textures and materials are appealing to our sense of touch in daily life. What makes us intuitively feel like touchingthese particular things? Haptic invitations of such materials have rarely been investigated. The present report identifies the relationships
between the visual and sensory properties of textures and their haptic invitations. We used 24 artificial clay textures that were varied
along four visual factors, and quantified the degrees of haptic invitations of these textures using a ranking approach. Multiple regression
analyses were performed to investigate the relationships between the degrees of haptic invitations of textures and texture factors. The
surface glossiness and shape patterns of textures strongly affected the degrees of haptic invitations of those textures, but surface colors
had little impact. As to the sensory factors yielded by semantic differential method, the glossless, dry, sticky, and simple factors
strongly affected the textures’ degrees of haptic invitations. Furthermore, we found that apparent comfort is intimately related to theattractiveness of textures. Visual and sensory factors captured 68% and 75% of the variance in subjective attractiveness, respectively.
These results suggest that the visual and sensory factors associated with textures are useful for designing textures that people findattractive. In addition to these general trends of haptic invitations, individual preferences were classified into a few groups. The preferences of majority were affected by glossiness of surfaces whereas there were roughness- and smoothness-sensitive groups.
Keywords: Haptic Invitation, Sensory Evaluation, Normalized-rank Approach, Apparent Comfort, Textural Factors

surface colors, gloss patterns and surface roughness may
directly induce haptic invitations. Moreover, haptic
invitations of textures might be determined via humansensory processing. For example, perceived roughness or
glossiness may influence haptic invitations of textures.
Such factors are acquired through sensory evaluation of
textures. This study began with the hypothesis that haptic
invitations of textures were related to the visual andsensory properties of textures. Participants did not touchtextures. They only looked at textures and judged theirhaptic invitation. We investigated general trends in thehaptic invitation of textures. These avenues of investigation were grounded in the authors’ pilot researches with asmall number of participants [2, 3]. The present article is areport of complete experiments with a sufficient numberof participants and a newly designed experiment to test
the impact of surface colors that generally influence
human affections. Pursuing the effects of colors is significant because the color is one of the most common factors
available for package designs.
Related studies on the effects of properties of textureson preferences: Many studies have examined the effectsof the physical and sensory characteristics of textures on
people’s preferences for them. In terms of product design,
Winakor et al. studied the effect of the physical characteristics of textile materials on customer preferences forwoven cotton and polyester fabrics [4]. The relationships
between materials and preferences for those materials
have also been studied with regard to wrapping paper [5],1. INTRODUCTION
Certain textures and materials are appealing to thehuman sense of touch in daily life. Well-polished metal
surfaces and finely woven clothes may be examples ofsuch materials. What types of texture properties appeal
to human touch? What makes us intuitively feel liketouching these? Haptic invitations of such materials haverarely been investigated. In this study, we identify theproperties of materials that appeal to human touch andinvestigate the extent to which the linear combination ofthese properties can describe haptic invitations of certain
textures. The findings of this study can be applied, forexample, to commercial products in stores in order toimprove their appeal to human touch. Such products
potentially garner consumers’ attention. Furthermore, inpublic places such as train stations or commercial facilities,
poster and flyer advertisements with such textures could
be used in order to attract the attentions of passersby. Peckand Wiggins suggested that textures had positive affective
influences on human attitude or behavior to brochures [1].
Their study represents an availability of textures that
invite human touch. The use of appealing textures would
be great applications of human factors research. This
study is a first step in identifying properties of suchappealing textures.
Textures can induce haptic invitations through appearance alone. The visual factors of textures, which include
Received 2012.12.06
Accepted 2013.05.20

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Copyright © 2013 Japan Society of Kansei Engineering.
All Rights Reserved.

International Journal of Affective Engineering Vol.12 No.3

sleep wear [6], and car seat fabrics [7]. Kawabata andNiwa proposed a method for predicting human preferences for clothing fabrics from the fabrics’ physicalcharacteristics [8]. A consumer’s preference is treated as
an integrated sensory assessment of materials. For example, in the case of cloth for suits or t-shirts, the assessment
is affected by several factors, including breathability,
water absorption, weight of the cloth, or comfort to thetouch. Such preferences are totally different from thehaptic invitation of textures.
Related studies on desire to touch: The desire to touchproducts for hedonic reasons was studied by Peck andcolleagues [9, 1]. They measured a hedonic-oriented
aspect in which customers feel inclined to touch products
for their own enjoyment. They examined personal
behaviors that indicate the extent to which a person tends
to touch products for enjoyment. However, the haptic
invitation of textures in the present study indexes theextent to which certain texture properties invite touch,which is a measure of a texture. Therefore, the humanbehaviors investigated as the “desire to touch” arecompletely different from the textures’ behaviors as the“haptic invitation” in our studies.
Recently, Klatzky and Peck [10] conducted a study
related to our previous ones [2, 3]. They investigated theextent to which three-dimensional objects invited humantouch whereas in the present study we investigatedtextures that appeal to human touch. Klatzky and Peckused an index based on subjective ratings assigned byparticipants to individual objects. In contrast, the degreeof haptic invitation in our study was quantified using aranking method. It is unknown that both indices capture
the equal information. In terms of the time required for themeasurement, our method is more participant-friendly.
Nonetheless, we do not stress the novelty of our index.
The major difference between our study and the one by
Klatzky and Peck is in the factors to be investigated:textures or object shapes.

limits, we prepared 24 textures that varied along four
visual factors: surface color, gloss pattern, surface shape
type, and surface ridge/groove width. These four factors
are commonly studied in the design of packaging paper
and plastic used in products. They are potentially available to serve as design factors for packing materials. We
used light clay (Hearty Soft White, Padico; Tokyo,
Japan) as the texture material. The clay was molded into
55.0 mm × 55.0 mm × 5.0 mm flat plates using aluminum
frame pairs. The surface color was either blue or orange,as the clay was mixed with paint before molding. The
blue-orange color variation is a complementary relationship in the Munsell color system. These colors were
expected to cause larger variation in sensory evaluations.
The blue (Phthalocyanine Blue, Liquitex; Ohio, USA)and orange (Scarlet Red, Liquitex; Ohio, USA) paints
were (4.0BP, 1.5, 7), and (8.0R, 5.0, 13), respectively, in
the Munsell color presentation. The mixing ratio was
100 g clay to 1.25 mL paint. Both glossy and glossless
textures were prepared. To make the textures glossy, theplates were varnished (Sealer Super Gloss, Padico;Tokyo, Japan) after being colored, molded, and dried.
The JIS (Japanese Industrial Standards) specular gloss
values of the textures were 2.4% and 94.2% for theglossless and glossy blue, respectively; the same values
were 1.7% and 85.1% for the glossless and glossy
orange, respectively. As shown in Figure 1, we used two
patterns; gridded and striped. The groove and ridge
widths were 0.5, 1.0, or 2.0 mm. These factors relating tosurface shapes are easily reproducible in designing
products. In total, 24 types of textures were prepared(2 colors × 2 gloss patterns × 2 shape types × 3 ridge andgroove widths). The photos of these textures are shownin Figure 2.

2. STIMULUS: VISUAL FACTORS OF TEXTURES
Haptic invitation may depend on the individual
predispositions of participants. For example, those who
are familiar with small mammals may feel inclined totouch animal furs. In order to limit the influence ofindividual background on the intensity of haptic invitation, it is best for textures used in such experiments toavoid association with specific entities. Therefore, weused simple clay plates with textured surfaces as thestimuli in this study.
It would be ideal to investigate the influence of as many
visual factors as possible. However, due to practicalFigure 1: Clay sample textures376

International Journal of Affective Engineering Vol.12 No.3
Visual and Sensory Properties of Textures that Appeal to Human Touch

3.1 Task 1: Sensory Factors of Textures
3.1.1 Method: Sensory evaluation
In order to quantify the sensory properties of textures,
we conducted sensory evaluations using an SD method.
Participants evaluated each of the 24 textures only once
using five-point scales anchored in terms of adjective
pairs, such as “rough-smooth” without time restriction.
The adjective pairs used in the experiments were chosenin accordance with studies on visual and haptic perception [11-18]. We provided both English and Japaneseterms on the evaluation sheets. We conducted preliminary
experiments to remove and merge candidate adjective
pairs according to their appropriateness for the textures inthis study. For example, we removed adjective pairs whosescores did not vary according to differences in texture,such as “thick-thin.” In addition, we merged adjective
pairs with similar meanings such as “shiny-matte” and“glossy-dull.” This process led to the final list of 15 adjective pairs shown in Table 1.
As shown in Figure 1b, a large matte white plate with a
50 mm × 50 mm square window was placed on top of eachsample so that the participants could see only the textured
surfaces and not the sides of the samples. The distance toa texture from a participant was approximately 0.5 m. The
participants were instructed to keep their head positions
fixed in order to maintain the relative position between thehead and the samples. The textures and adjective pairs
were presented to each participant in a randomly orderedfashion.
We conducted the experiments during the summer
months. The laboratory temperature and humidity wereapproximately 28°C and 65%, respectively. The textures
were placed under constant illumination of approximately
700 lx by a fluorescent light in an office room blocking
sunlight.

Figure 2: Photos of textures

The visual factors of the textures were quantified asscores. In order to compare regression coefficients ofvisual factor scores in multiple regression analysis at later
sections, the scores were normalized to a mean of 0 and avariance of 1 for each of the factors: surface color (1, blue;-1, orange), gloss (1, glossless; -1, glossy), shape type(1, stripe; -1, grid), and ridge/groove width (-1.07, 0.5mm; -0.27, 1.0 mm; 1.34, 2.0 mm).
3. EXPERIMENT 1: RELATIONSHIPS BETWEENSENSORY/VISUAL FACTORS OF TEXTURESAND HAPTIC INVITATIONS OF TEXTURES
In experiment 1, we specified the sensory properties oftextures and haptic invitations of textures through twotasks. In both tasks, participants did not touch textures but
evaluated them on the basis of visual appearances. In Task
1, participants evaluated textures one after the other using
a semantic differential (SD) method. We then applied
factor analysis to the resulting data to extract independent
sensory factors. In Task 2, participants ranked all of the
textures in order of the intensity of their haptic invitations.
Based on these rankings, we calculated the degrees of
haptic invitation of each texture. Finally, we investigated
the relationships between degrees of haptic invitation of
the textures and the textures’ visual and sensory factors
using multiple regression analysis. The experiments andprocedures described in this report, including participant
recruitment, were approved by the ethical committee of
Nagoya University. Sixteen university students (9 males
and 7 females; approximately 20 years of ages) volunteered
to participate. To avoid ordering effects, eight participants
performed Task 1 first, followed by Task 2; the other eightparticipants performed Task 2 first, followed by Task 1.

3.1.2 Factor analysis
We used a five-point adjective scale in Task 1. The
values for each adjective pair were normalized withinsingle participants. The values were then averaged acrossall participants. To decrease the number of variables usedin later analysis, we applied factor analysis to the values
Table 1: 15 adjective pairs used in sensory evaluation
harshglossyvague
comfortable
dry
rough
slippery
sharp

377

-

not harsh
glosslessclear
uncomfortablewetsmoothstickyblunt

unevenelegant
dark
soft
vivid
warm
simple-flat
inelegant
light
hard
colorlesscoldcomplexInternational Journal of Affective Engineering Vol.12 No.3

3.2 Task 2: Degrees of Haptic Invitation for Textures
We focus on the fact that it is difficult for participants
to quantify degrees of haptic invitation using visual
analog scales or magnitude estimation methods,
although participants can confidently make judgments
about which of several textures are attractive to them.
Accordingly, we introduced a ranking method that allows
participants to rank textures in order of intensity of theirhaptic invitations. We then exploited a normalized-rankapproach [19] to convert the texture ranks to interval
scales. This approach is applicable to the texture stimuliof this study in which we exhaustively manipulated four
visual factors to produce texture stimuli. A paired
comparison method is another method of estimating themagnitude of haptic invitation; however, the paired
comparison method requires a large number of trials toensure reliability.

and extracted the common factors that provide synthesisof strongly correlated variables. xi was the vector of evaluation values of p (p = 15) adjective pairs for the texture
specified by i. xi was decomposed into m common factor
scores fi and unique factor scores ei:(1)where the factor loadings A explain the strength of therelationships between common factors and adjective
pairs. The number of samples is denoted by n (n = 24).
The factor loadings are estimated by the maximum likelihood method. We applied varimax rotation to the factor
loadings to facilitate interpretation of the relationships
between factors and adjective pairs.
3.1.3 Results: Factor loadings of 15 adjective pairs
The factor loadings and each factor’s cumulative contribution rates are shown in Table 2. We adopted a four-factor
model (m = 4) because the cumulative contribution rate
was nearly saturated when m = 4. Cells with absolutefactor loadings of 0.6 or above are highlighted in gray.
We named Factor 1 the “glossless, dry and sticky factor.”
This factor was affected by the fine roughness of thesurface, which was associated with dryness, glossiness,and slipperiness. Factor 2 was the “uneven and roughfactor” characterized by the macroscopic roughness of thesurface. Factors 3 and 4 were the “dark and cold factor,”and “simple and comfortable factor,” respectively.

3.2.1 Method: Ranking 24 textures
Twenty-four samples were simultaneously presented toeach participant, which allowed him/her to evaluate therelative differences in the textures. At first, textures werearranged in a random array of size 4 × 6. Then, theparticipants ranked the textures only once in terms of theintensity of their haptic invitations without a time limit.
Each participant was allowed to give the same rank tomultiple textures if he/she was unable to rank all of the
textures without duplicating ranks.
3.2.2 Data analysis: Normalized-rank approach
We converted the ranks of the textures to interval scales
using the normalized-rank approach [19]. We definedthese interval scales as the degrees of haptic invitation of
the textures. The degree of the kth ranked texture was
assigned as the expected value of the kth largest observation in a sample of size n from a standard normal
population. The degree of the kth ranked texture wasdetermined by

Table 2: Results of factor analysis:
Factor loadings of 15 adjective pairs
GlossyDryHarshSlippery
Uneven
Rough
Soft
Dark
Cold
Vivid
SimpleComfortable
Elegant
Sharp
Vague
Contributing
rates
Cumulative
contributing
rate
FeaturingnameFactor 1-0.9180.916
0.839-0.726
0.115
0.407
0.187
0.235
-0.336-0.423
0.020
0.434
0.405
-0.021-0.339

Factor 2-0.2760.114
0.243-0.598
0.861
0.756
0.726
-0.023-0.111
0.026
0.291-0.094-0.331-0.611-0.543

Factor 3-0.068-0.1350.215-0.122-0.0470.179-0.2410.969
0.891-0.8450.025-0.082-0.538-0.0180.029

Factor 4-0.2660.289-0.006-0.158
0.306
0.097
0.165
-0.034
0.037
0.044
0.862
0.667
0.483
0.349
-0.615

0.263

0.215

0.195

0.149

0.263

0.478

0.673

0.822

E ( xk |n ) =∞n!
x ⋅ a ( x ) ⋅ b ( x ) ⋅ φ ( x ) dx (2)( n − k )!( k − 1)! −∞∫a ( x ) = 1 / 2 − Φ ( x ) k −1b ( x ) = 1 / 2 + Φ ( x ) n−k1

φ ( x) = 1 2
− x 


(3)
(4)

e 2

(5)

Φ ( x ) = ∫ φ ( z ) dz.

(6)

2π
x

0

Glossless,
Simple &Uneven & Dark & cold
dry & sticky
comfortablerough fac.
fac.
fac.
fac.

The degrees of haptic invitation of a certain texture wereaveraged across the participants.

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International Journal of Affective Engineering Vol.12 No.3
Visual and Sensory Properties of Textures that Appeal to Human Touch

respectively; the adjusted value of R2 thereby obtained
was 0.68. The standard partial regression coefficients areshown in Table 3.
Glossiness: We performed t-tests to see whether the
standard partial regression coefficients were significantly
different from zero. A significant correlation between
surface gloss and degree of affinity was observed (twotailed t-test, t (19) = 5.29, p = 4.14 × 10−5). In other words,
glossiness decreased the degrees of haptic invitation of
textures. One possible explanation of this result, indicatedby participants’ reported introspection that was recorded
after all experiments, is that the majority of participants
were disinclined to touch glossy textures because they areoften associated with slimy surfaces. These results mayvary according to the type of materials. For example, inthe case of woolly materials, surface glossiness will not be
associated with slimy feelings.
Shape type: There was also a significant correlation
between the shape type (stripe/grid) of the textures andthe degrees of haptic invitation of textures (two-tailed
t-test, t (19) = 4.69, p = 1.59 × 10 −4): the degrees of haptic
invitation of striped textures were greater than those forgridded textures. According to the introspection, participants may have expected that striped textures would
provide stronger tactile stimuli than gridded ones. This isconsistent with the observation that the majority ofparticipants reported that they would touch the striped
textures so that their fingers moved perpendicularly to thegroove orientation. In such a case, their perceived roughness of striped textures would exceed that of the gridded
ones. Thus, we speculate that moderately intense tactile
stimuli appealed to human touch.
Ridge and groove width: Ridge and groove widths(0.5/1.0/2.0 mm) did not impact the degrees of haptic invitation of textures (two-tailed t-test, t(19) = 1.80, p = 0.09).

3.2.3 Results: Degrees of haptic invitation for 24
textures
Figure 3 shows the degrees of haptic invitation obtained
during Task 2. The error bars indicate the standard deviations across all participants. The textures are arranged indescending order of the degree. The majority of the
textures for which participants indicated high degrees of
haptic invitation were glossless textures. Surface gloss wasconsidered to affect haptic invitation more significantly
than other visual factors under the experimental conditions of this study. In terms of shape type, participants’haptic invitation of striped textures was higher than that ofgridded textures. In terms of ridge and groove width, thedegrees of haptic invitation of textures with small widths
were slightly higher than the degrees of haptic invitationof those with large widths. It was hardly possible toobserve the effects of surface colors on haptic invitation.
3.3 Relationships between Degrees of Haptic Invitation
and Factors of Textures
To investigate the relationships between the degrees of
haptic invitation of textures and texture factors, we
performed multiple regression analysis. This analysis
connected the degrees of haptic invitation with the visualfactors of textures and also connected the degrees of
haptic invitation of the textures with the sensory factors of
the textures. The analysis was applied to the standardized
values. In addition, we obtained the correlation coefficients between the visual and sensory factor scores.
3.3.1 Relationships between Degrees of Haptic
Invitation and Visual Factors
We conducted multiple regression analysis with thedegrees of haptic invitation and the visual factor scores oftextures as the objective and explanatory variables,

Figure 3: Degrees of haptic invitation for 24 textures379

International Journal of Affective Engineering Vol.12 No.3

Table 3: Regression coefficients of visual factor scores anddegrees of haptic invitation. The asterisk ∗∗∗ indicates thesignificance levels of p < 0.001.

Regression
coefficients

Color(+,Blue;-,Orange)

Gloss(+,Glossless;-,Glossy)

Shape type(+,Stripe;-,Grid)Ridge andgroove width

0.049

0.609∗∗∗

0.540∗∗∗-0.207

invitation of textures were found. The relationshipbetween Factor 2 (uneven) and haptic invitation was not
significant (two-tailed t-test, t(19) = −1.45, p = 0.16).
Factor 3 (dark & cold) also had no significant impact on
haptic invitation (two-tailed t-test, t (19) = 0.04,
p = 0.97). Thus, participants reported higher degrees of
haptic invitation of textures described as glossless, dry,sticky, and simple. Interestingly, though Factor 2(uneven) was the second most significant contributing
factor to visual recognition of texture, it did not contribute to the degrees of haptic invitation of textures. In
contrast, Factor 4 (simple) was a minor contributing
factor to texture recognition, but it strongly influenced
haptic invitation.

Table 4: Regression coefficients of sensory factor scores anddegrees of haptic invitation

Regression
coefficients

Factor 1
Glossless
Dry
StickyFactor 2
Uneven,RoughFactor 3
Cold
Dark

Factor 4
SimpleComfortable

0.476∗∗∗-0.1590.004

0.773∗∗∗

3.3.3 Haptic invitation comes from comfort
To identify influential adjective term pairs, we investigated the correlation coefficients between the degrees of
haptic invitation and the ratings of adjective term pairs.
The results of this analysis revealed that the correlation
coefficient for the “comfortable-uncomfortable” pair was
0.82; that was the highest value among the correlation
coefficients between haptic invitation and individual
adjective term pairs. The ratings for this pair indicate
apparent comfort and it was included in the most influential factor of “simple and comfortable.” A texture’s
apparent comfort potentially affects its attractiveness tohuman touch, consistent with results obtained by Klatzky
and Peck [10]. Their index for attractiveness included the
response to the statement “touching this object would feelgood” which appears to yield similar results to the“comfortable-uncomfortable” pair used in the present
study. The second-highest correlation coefficient was thatbetween the haptic invitation of textures and the “dry-wet”
pair (0.65); that pair was extracted as Factor 1 (glossless,dry & sticky).

Surface color: Surface colors (blue/orange) also failed
to impact the degrees of haptic invitation of textures (twotailed t-test, t(19) = 0.43, p = 0.67).
According to these analyses, the degrees of haptic invitation of glossless and striped textures are expected tohave high values. This estimate is consistent with theresults shown in Figure 2. The four textures for which
participants had the largest degrees of haptic invitation
were glossless and striped textures, whereas the fivetextures for which participants had the five smallest
degrees of haptic invitation were glossy and gridded
textures.
The present effects of surface roughness on haptic invitation differ from previous findings [10], which showedthat smooth surfaces invited human touch more thanbumpy ones. In our study, ridge and groove widths did not
impact the haptic invitations of textures. We speculate that
this is due to differences in touching methods. In the studyof [10], touch may have represented grasping, whereas inour study, touch meant stroking. Consequently participants in [10] may have regarded surface bumpiness as an
impediment to grasping.

3.3.4 Correlations between visual and sensory factors
The correlations between the visual and sensory factors
are presented in Table 5. Factor 1 (glossless, dry & sticky)
was related to the surface gloss. Glossy textures had highFactor 1 values. Factor 2 (uneven) was influenced by ridgeand groove widths, indicating that coarser surface patterns
were perceived as more uneven. The correlation between
Factor 3 (dark & cold) and surface color was strong.
Finally, Factor 4 (simple) was affected by the shape typeused to create the texture, with striped textures more
likely to be perceived as simple than gridded textures.
Figure 4 shows these relationships between the degreesof haptic invitation of textures and the visual and sensory
factors of those textures. The line width represents relationship strength and corresponds to the absolute values in

3.3.2 Relationships between degrees of haptic
invitation and sensory factors
We conducted multiple regression analysis using
degrees of haptic invitation of textures as the objective
variable and the texture sensory factor score as the
explanatory variable; this model yielded an adjusted R2
value of 0.75. In this study, sensory factors had more
explainable utility for haptic invitation than visualfactors of which R2 was 0.68. Table 4 lists the standard
partial regression coefficients resulting from this multiple regression analysis. Significant effects of Factor 1(glossless, dry and sticky) (two-tailed t-test, t (19) = 4.48,
p = 2.56 × 10−4) and Factor 4 (simple and comfortable)(two-tailed t-test, t(19) = 6.93, p = 1.33 × 10−6) on haptic

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Visual and Sensory Properties of Textures that Appeal to Human Touch

Table 5: Correlation coefficients between visual and sensory
factor scores

Color

Factor 1

Factor 2

Factor 3

Factor 4-0.066-0.004

0.956

0.086

Gloss

0.913

0.276

0.033

0.301

Shape type-0.183-0.096-0.062

0.807

R & G width-0.2960.771-0.0400.201

Figure 5: Distribution of participants in two dimensions.
Degrees of haptic invitations of participants in GroupA and B are affected by the ridge and groove width(Smooth/Rough). Those in Group C1 and C2 areaffected by the glossiness (Glossless/Glossy).

We applied factor analysis to the degrees of haptic invitation of textures and placed each participant within a
two-dimensional space (Figure 5). We then classified
participants into three groups (A, B, and C) on the basis of
the distribution of participants in two dimensions; GroupC was the major group, and Groups A and B were minorgroups.
The participants in Group A exhibited high haptic invitation of textures whose ridge and groove widths were
small. For one participant (P1) in Group A, the correlation
coefficient between the ridge and groove width anddegrees of haptic invitation was -0.886. However, forparticipants in Group B, the degrees of haptic invitation of
uneven textures were high. For example, the correlation
coefficient for one participant (P2) in Group B was 0.786.
Most of the participants had small values on Dimension
1; we categorized these participants as Group C, but they
were widely distributed in Dimension 2. Therefore, we
divided Group C into Groups: C1 and C2. In Group C1,
the degrees of haptic invitation of glossless textures were
high. For one participant (P3) in Group C1, the correlation
coefficient between glossiness and degrees of haptic invitation was 0.672. Group C2 participants were attracted byglossy textures, with one participant (P4) exhibiting acorrelation coefficient of -0.616. Although most participants belonged to Group C1, some variations in haptic
invitation were observed. Thus, while this study focusedon general trends, individual differences can be an intrinsic topic of haptic invitation.

Figure 4: Relationships between sensory factors, visual factorsof textures, and degrees of haptic invitation

Tables 3, 4, and 5. The relationships between the degreesof haptic invitation of textures and the visual and sensory
factors of the textures were effectively quantified under
the current study’s stimuli set.
We found that visual and sensory factors captured 68%
and 75% of the variance in haptic invitation of textures,
respectively. The results support the argument that haptic
invitation of textures is generally controlled by visualand sensory factors. The fact that the remaining
20%-30% of the variance could not be described bythese factors may be explained by the visual and adjective
terms that were omitted from this study. Individual
differences in decision criteria between the two experimental tasks may have also contributed to the residualsof the regression analyses.
3.4 Individual Differences in Haptic Invitation of
Textures
The standard deviations of the degrees of haptic invitation of textures in Sec. 3.2.3 were not small despite the useof only simple textures to limit the impact of personal
cultural background. In order to investigate the individual
differences in the degrees of haptic invitation of textures,
we clustered and characterized the 16 participants in termsof their degrees of haptic invitation using factor analysis.

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4. EXPERIMENT 2: RELATIONSHIPS BETWEENSURFACE COLORS AND HAPTIC INVITATION
Experiment 1 did not exhibit a significant relationshipbetween the degrees of haptic invitation of textures andthe two surface colors (blue/orange). However, we should
not conclude that surface colors do not influence haptic
invitation, because, just two colors were tested. In addition, in the Munsell color system, color variations are notclassified in one-dimensional space. Furthermore, theeffects of hues on human feelings have been generally
admitted [20-22]. For cases in which color yielded nosignificant results, we use a two-phased approach to draw
conclusions about the significance of factors. In Experiment 2, we intensively focus on a single factor, i.e., color,
and we increase the number of surface colors in order totest the contribution of surface color more thoroughly.

Figure 6: Hue circle in the Munsell color system

4.1 Measurement of Haptic Invitation of Five-Colored
Textures
Participants ranked textures differing from those used inExperiment 1 in order of the degrees of haptic invitationof the textures. We crossed color and ridge/groove width
to generate the 10 stimuli (5 colors × 2 ridge and groove
widths). The textures had five different surface colors:
blue, orange, purple, green, and yellow. The blue andorange paints were the same as those used in Experiment
1. The purple (Dioxazine Purple, Liquitex; Ohio, USA),
green (Permanent Green Light, Liquitex; Ohio, USA) andyellow (Yellow Medium Azo, Liquitex; Ohio, USA)
paints were (5.6P, 1.5, 1), (1.2G, 4.9, 10), and (3.7Y, 8.2,13), respectively, in the Munsell color presentation. These
five colors are nearly equally spaced in the Munsell color
system as shown in Figure 6. The mixing ratio was thesame as that used in Experiment 1. All textures wereglossless and striped. The groove and ridge widths were
either 1.0 or 2.0 mm. We used the same normalized-rankapproach as in Experiment 1 to convert the ranks of thedegrees of haptic invitation of textures.

Figure 7: Degrees of haptic invitation of 10 textures:
5 different surface colors

within the textures used in this study, as was the effect ofridge and groove widths.
4.3 Discussion: Effects of Surface Colors on Haptic
Invitation of Textures
Colors have been reported to have a variety of effects onhuman feelings. Some have reported that colors with longwavelengths, such as red, yellow, and orange, are apparently warmer than colors with short wavelengths, such as
violet, blue, and green [20, 21]. Also, yellow is associatedwith smooth and soft textures [22]. Hence, hues seem tobe related to Factor 2 (uneven) and Factor 3 (dark & cold).
The results of Experiment 1 showed that these two factors
rarely affect the degrees of haptic invitation of textures.
Therefore, from these literature and the results of bothexperiments, it is reasonable to conclude that the hues oftextures insignificantly affect their haptic invitations. Thisis a good implication for package design because color
design and haptic invitation can be decoupled. However,
we should note that brightness (which is related to apparent surface glossiness) potentially affects the haptic
invitation of textures.

4.2 Results of Experiment 2: Degrees of Haptic
Invitation of 10 Textures
Figure 7 shows the degrees of affinity obtained during
Experiment 2. The textures are arranged in descendingorder of haptic invitation. We performed a two-way
ANOVA with surface colors and ridge and groove widths
as the explanatory variables and degrees of haptic invitation
as the objective variable. The results indicated no significant effect of surface color (F(4,150) = 1.15, p = 0.34;
η2 = 0.030) or ridge and groove width (F(1,150) = 0.82,
p = 0.37; η2 = 0.005) on haptic invitation. The effect of
surface color on haptic invitation was therefore negligible

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Visual and Sensory Properties of Textures that Appeal to Human Touch

5. CONCLUSION

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We investigated visual and sensory properties of texturesthat appeal to human touch. We used sample textures in amanner that allowed us to control four visual factors(surface color, gloss, shape type, and ridge/groove width).
Of the tested visual factors, glossiness and surface shapemost strongly affected the degrees of haptic invitation of
textures. Further experimentation indicated that surface
colors did not influence the haptic invitation of textures.
Regarding the influence of sensory factors, Factor 1 (glossless, dry and sticky) and Factor 4 (simple and comfortable)
were strongly related to haptic invitation. These factors
captured 68%-75% of the variance in haptic invitation.
In product design, the number of visual factors available
for manipulation is limited. Under such conditions, thepresent method enables the design of products or texturesthat are appealing to human touch. Verification of thismethod through real marketing research in the design ofcommercial products is an upcoming challenge.
ACKNOWLEDGEMENTS
This work was in part supported by MEXT KAKENHI
24700192. The authors thank Prof. Susumu Hara and
Dr. Yasuhiro Akiyama, who discussed this study.

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Hikaru NAGANO

Yoji YAMADA

Hikaru Nagano received B.S. and M.S. degrees inengineering in 2010 and 2012, respectively, from
Nagoya University. He is currently a Ph.D. candidatein the Department of Mechanical Science andEngineering, Nagoya University, as well as a
Research Fellow with the Japan Society for the
Promotion of Science, Tokyo, Japan, from April 2013. His researchinterests include human perception, haptics.

Yoji Yamada received M.S. degrees in engineeringfrom both Nagoya University, Japan, and the
University of Texas in 1983, and he received a Ph.D.
degree from the Tokyo Institute of Technology,
Japan, in 1990. He has been an associate professor
at the Toyota Technological Institute, Nagoya,Japan since 1983. In 2004, he joined the National Institute of Advanced
Industrial and Science Technology (AIST), as a group leader of the
Safety Intelligence Research Group at the Intelligent Systems ResearchInstitute. In 2008, he moved to the Department of Mechanical Scienceand Engineering, Graduate School of Engineering, Nagoya University,
as a professor.

Shogo OKAMOTO
Shogo Okamoto received a B.S. degree in engineering from Kobe University in 2005, and M.S. and
Ph.D. degrees in information sciences in 2007 and2010, respectively, from the Graduate School ofInformation Sciences, Tohoku University. Since
2010, he has been an assistant professor at theGraduate School of Engineering, Nagoya University. His researchinterests include haptic interfaces and human-assist technology.

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