Innovation Framework Illustration – Obrist et al. Temporal, Affective, and Embodied Characteristics of Taste Experiences: A Framework for Design

Temporal, Affective, and Embodied Characteristics of

Taste Experiences: A Framework for Design

Marianna Obrist1,2, Rob Comber1, Sriram Subramanian3, Betina Piqueras-Fiszman4, Carlos Velasco4, Charles Spence4

m.obrist@sussex.ac.uk | rob.comber@ncl.ac.uk | sriram@cs.bris.ac.uk |

betina.piqueras-fiszman@psy.ox.ac.uk | carlos.velasco@psy.ox.ac.uk | charles.spence@psy.ox.ac.uk

1Culture Lab, School of Computing Science

Newcastle University, UK

2School of Engineering and Informatics

University of Sussex, UK

3Deptartment of Computer Science,

University of Bristol, UK

4Department of Experimental Psychology,

University of Oxford, UK

ABSTRACT

We present rich descriptions of taste experience through an

analysis of the diachronic and synchronic experiences of

each of the five basic taste qualities: sweet, sour, salt, bitter,

and umami. Our findings, based on a combination of user

experience evaluation techniques highlight three main

themes: temporality, affective reactions, and embodiment.

Comment 1

We present the taste characteristics as a framework for

design and discuss each taste in order to elucidate the

design qualities of individual taste experiences.

Comment 2

These findings add a semantic understanding of taste experiences,

their temporality enhanced through descriptions of the

affective reactions and embodiment that the five basic tastes

elicit.

Comment 3

These findings are discussed on the basis of

established psychological and behavioral phenomena,

highlighting the potential for taste-enhanced design.

Comment 4

Author Keywords

Taste; user experience; taste experiences; sensory research;

explicitation interview technique; sensual evaluation tool.

ACM Classification Keywords

H.5.2 Information interfaces and presentation (e.g., HCI):

Miscellaneous.

INTRODUCTION

Experts in taste perception agree on at least five basic tastes

[40]. Beyond this, however, we lack insights into the rich

experience of these tastes. This lack of experiential

understanding extends beyond HCI, as sensory researchers

have also acknowledged that: What is not well researched

is the link between the food that goes into our mouth and

what we think of it [12]. There is a growing interest in taste

within the HCI community [e.g., 16,17,18,22,27,28],

particularly relating to technical challenges in designing for

taste stimulation and one-off designs to enhance user

experiences through the manipulation of taste.

There is a need for a more systematic study of people’s

taste experiences and their specific characteristics in order

to make a fuller use of this sense in future taste-enhanced

technologies. This paper stands as a first step in addressing

this need. Drawing on neuroscience and sensory research in

combination with user experience evaluation techniques,

we investigated how all five basic tastes are experienced at

a given time (synchronic) and how they evolve over time

(diachronic). We used pure tastants (i.e., that have no smell

or visual qualities) with an explicitation interview technique

[41] designed to encourage the participants to verbalize

their experiences. Additionally, we used physical objects

from the Sensual Evaluation Instrument [13] to elicit

affective responses, and create a flexible, non-verbal

channel of communication between the user and designers.

This paper makes a number of contributions: First, we

provide a rich description of subjective taste experiences

along both the diachronic and synchronic characteristics of

the five basic tastes.

 

Second, these taste characteristics

establish a framework for taste experiences and elucidate

the potential design qualities of individual tastes.

 

We demonstrate how each quality can be described along three

main themes: temporality, affective reactions, and

embodiment. Third, our findings extend human-computer

interaction research on taste through a user experience

perspective. Overall, our findings provide interaction

designers and user experience researchers with a richer

understanding of taste experiences and their specific power

to influence human behavior and decision-making. The

framework presented here enables the HCI community to

think and talk about taste in the design of interactive

systems in a fine-grained manner.

RELATED WORK

This section provides an overview of the human sense of

taste and its relevance for HCI based on ongoing research.

The sense of taste

Sensory researchers and neuroscientists agree on five basic

tastes (sweet, sour, salty, bitter and umami), and a

‘gustotopic map’ linking these classes of receptors with

particular brain areas is currently being developed [40].

However, despite breakthroughs in understanding the sense

of taste, scientists have still not approached the

phenomenology of taste nor developed a semantic

understanding of how taste is experienced [30].

Although a wide body of sensory research has studied the temporal

evolution of taste perception using labeled intensity scales

[e.g., 1,8] and more specific time-intensity sensory

evaluation scales [26], insights are limited to the

quantification of temporal responses to perceived taste

intensities. Such scale-based evaluations leave us

uninformed as to the subjective qualities that lie behind the

ratings of the perceived taste experience over time.

Recently, neuroscientists have studied taste-specific

temporal profiles by comparing sensory evaluation scales

with functional MRI (fMRI) data [19]. Their results

suggested that salty tastes change more rapidly than sweet

tastes in the cerebral cortex, and confirm the same patterns

that have been observed using time–intensity sensory

evaluation [19]. While such results are intriguing, they

cannot explain the differences in experienced tastes.

To account for subjective differences, the ‘taster status’

measure has been introduced [2,6]. By means of such tests,

it is possible to identify participants’ subjective sensitivity

to bitter tastes and to distinguish between supertasters (25%

of population), medium tasters (50%), and non-tasters

(25%) [3]. Taster status has been considered to partially

explain why some consumers like certain foods more than

others and how they describe the way they experience them.

Food-interaction design

The last few years have seen increasing interest in

designing human-food interaction in HCI [e.g., 4,9,11,33].

Such research looks to position human-food interaction

within the wider spectrum of social, environmental, and

physiological influences on our food practices. In this area,

there is a growing realization of the potential for new

technologies to support pleasurable experiences around

food [20,35], and the potential for designers to draw on the

extensive research on multisensory experiences (i.e.,

auditory, tactile, visual, olfactory, and gustatory). Despite

this increased interest in food experience, we know little

about the richness of people’s taste experiences. The

majority of the studies on food experience combine taste

with other modalities, where taste is but one component

[e.g., 18,27,28].

For instance, Schifferstein et al. [31] elicited emotional

experiences across the different stages of food product

usage, from choosing a product in the supermarket through

to cooking and eating [31]. Taste experience is interwoven

with vision, touch, and olfaction, which, in combination

create multisensory food experiences. Desmet and

Schifferstein [5] also explored the emotions elicited through

eating and tasting food. They describe variables related to

food-evoked emotions, such as sensory features, product

type, food-related activities, context, and the agent (who

consumes, prepares, or produces). Due to the wide range of

influencing variables, it is not clear how well these findings

translate beyond the specific context of their studies.

Taste-enhanced technology

Technological advances in creating taste stimulations

[27,28] and one-off applications exploiting taste in games

[16] and other scenarios [18,22] demonstrate a growing

interest in the use of taste in interactive applications. For

instance, Ranasinghe et al. [27,28] developed a tongue

interface that creates taste through the combination of

electrical and thermal stimulation. They use electrical

pulses applied to the tongue. Verbal descriptors provided by

participants were, for instance, a ‘refreshing taste’ or ‘minty

taste’ in relation to the change in temperature. The authors

call for future work to understand the particularities of such

taste (flavor) experiences.

 

They focused on the introduction

of taste in digital communication to enhance long-distance

family relations and create remote co-presence and coliving

experiences (e.g., remote dining) [28].

 

Murer et al. [16] designed a gustatory game device,

LOLLio, which consists of an interactive lollipop that

serves as a haptic input device that dynamically changes its

taste between sweet and sour. Remote triggering of taste

while motion sensing with accelerometers allows LOLLio

to be used as an input modality. The authors identify

various ways in which taste could be used in an interaction,

such as to provide reward or punishment or else to provide

hidden information through taste stimuli. LOLLio was

evaluated in a game context with children [17]. Sweetness

was constantly used in the game session and sour stimuli

were used in combination with game mechanics to provide

‘negative reinforcement’. Their findings suggest an

enhanced playing experience through taste stimulation

motivating further explorations of such taste-enhanced

interaction experiences.

 

STUDY METHOD AND PROCEDURE

Sensory research provides important information regarding

the objective measures of taste perception, temporality, and

subjective sensitivity levels. Yet, an understanding of the

subjective understanding of taste experiences is missing.

 

This study explores the diachronic and synchronic structure

(explained below) of each of the five basic tastes.

Methodology

For our study, we combine two verbal and non-verbal user

experience and elicitation methods, the explicitation

interview technique (verbal method) and the ‘Sensual

Evaluation Instrument’ (non-verbal method).

The explicitation interview technique [41] is used to elicit

verbalizations of subjective experiences. This technique

helps to explore the unfolding of an experience over time,

the ‘diachronic’ dimension, and examines the specific

facets of the experience at a particular moment, the

‘synchronic’ structure (see also [24,39]). The value of this

interview technique lies in helping participants to express

their experiences at a specific moment. Participants are

encouraged to talk about the experiential (cognitive,

perceptive, sensory, and affective) aspects of the moment

without building on rational comments and explanations

[24].

Questions related to the diachronic structure help to

understand how the description of an experience unfolds

over time (e.g. “What happened after you opened the

door?” and “What did you perceive next?”). With respect to

the synchronic structure of an experience, the participant is

questioned about a particular moment (e.g. “At the moment

when you pushed the handle down, how did it feel?” or

“What else came in your mind?”). In comparison to open

questioning approaches, this technique is non-inducive but

directive [24] in the sense that it keeps the participant

talking about the experience without inducing any content;

it focuses on the structure of the experience, and directive,

as it keeps the participant focused on the singular

experience being explored. Although it is typically used

retrospectively to support the reconstruction of an

experience, it has also been used in-situ (e.g., [15,23]).

The Sensual Evaluation Instrument (SEI) is a non-verbal

tool that can be used to elicit users’ affective reactions [13].

SEI is composed of sculpted objects that can be held in the

hand, used by a person to indicate how they are feeling as

they interact with a system. The SEI includes eight objects

with different shapes, which represent various levels of

arousal and valence (positive and negative). Isbister et al.

[13] describe SEI objects as evoking and expressing a range

of emotions; they do not claim a direct mapping between

the objects and the mentioned emotions,

but emphasize the

benefit of the objects for stimulating expressiveness. The

value of the SEI is to elicit real-time, affective responses,

and to create a flexible, non-verbal channel of communication

between user and designers. The latter defines a key

advantage compared to other methods that are often limited

to verbalizations or visualizations that lack physicality.

Taste stimuli

The stimuli used for each taste are specified in Table 1.

Each stimulus was prepared as an odorless and colorless

water solution using a stock solution as specified in ISO

3972. We prepared the solutions according to the

specifications detailed by Hoehl et al. [10] and used

deionized water for the tastants. These compounds

standardised stimulus features and controlled for sensory

differences, such as texture, vision, etc. All of the solutions

were prepared the day before each study day. The

participants received 20 ml of each stimulus in a disposable

40 ml cup. A Latin square design was used to avoid order

bias [42].

Table 1. Stimuli used for the five main tastes, including the

stock solution (indicating the threshold specified in ISO 3972).

Participants

The study was conducted with 20 participants (nine female)

aged between 21-38 years (M=29.4, SD=5). Participants

were recruited based on the following criteria: not having

any food allergies, being non-smokers, not being pregnant,

and not having any sensory dysfunction (e.g., dysguesia, a

taste disorder), by self-report. The participants were

recruited through the staff list within the lead university. 16

participants were native English speakers, and the

remaining four were fluent in English. All participants gave

informed consent prior to the study.

Study set up and procedure

The participants were instructed and reminded 2 days prior

to the study not to eat spicy food 24 hours before the study

and not to drink or eat 1 hour before attending the study.

The study had 2 parts (see Figure 1): In the first part, we

applied the explicitation interview technique for all five

tastes; in the second part we introduced the SEI objects to

enhance the verbalizations for each taste.

In the first part, participants were given 5 minutes per

stimulus. They could take as many sips as they wanted of

the stimulus and were prompted with specific questions

about their taste experience (e.g., Could you describe what

you perceive? How does it feel in your mouth?). The aim

was to receive insights regarding the diachronic and

synchronic structure of the taste experience. We used this

technique in-situ in order to account for the rapidly

decaying sensory memory trace related to the human sense

of taste [21]. Before continuing with the next stimulus, the

participants were asked to have a sip of the deionized water

in order to cleanse their mouth. The same procedure was

repeated for all stimuli.

In the second part of the study, the participants were

instructed to match each taste experience to one or more of

the eight shapes inside the box. The participants could only

feel, and not see, the objects, to exclude any visual

influences and to focus on the mapping between ‘taste and

shape’ via the sense of touch. The participants were

instructed to select one or more or none of the shapes (they

could also reuse shapes for different tastes). Before going

through each taste stimulus again, the participants were

given the chance to put their hands into the box and

familiarize themselves with the 8 shapes.

Next they were asked to take a sip of water and start with

the first taste stimulus. They were asked to express the

thoughts they had in mind and to describe their choices or

lack thereof (if none of the shapes was selected). Finally,

the participants were asked to rate the pleasantness/

unpleasantness of the shapes on a four-point Likert scale

from ‘very pleasant’ to ‘very unpleasant’. They were also

asked about their personal favorites amongst the 5 taste

stimuli and their personal food preferences to support the

interpretation of the data.

In a final step, we tested the participants for their taster

status, which classified participants into supertaster, normal

tasters, and non-tasters. Overall, the study lasted one hour

and was audio/video recorded with the consent of the

participants. No incentives were paid to the participants.

Data analysis

All 20 tasting sessions were transcribed and a qualitative

analysis based on the transcripts was conducted. Two

researchers independently performed an open thematic

coding based on 5 cases (25%). The resulting themes were

discussed and an initial coding scheme was established.

Two more cases (10%) were coded independently leading

to a final coding scheme consisting of three main themes

(described in the next section), which were then applied to

the remaining 13 cases by both researchers. We also

performed a qualitative analysis of the mapping between

the SEI objects (see Figure 4) and the taste experiences,

captured through the transcripts and the visual material

from the recorded hand movements in the second part of the

study. Based on participants’ ratings of the shapes (their

physical pleasantness/unpleasantness) we could confirm

previous ratings of Isbister et al. [13] – the more spiky

shapes were rated as ‘unpleasant to slightly unpleasant’

(shapes 8,7,2), the more rounded shapes were rated ‘very

pleasant to pleasant’ (shapes 3,4,5,6), and only one shape

was perceived as ‘neutral’ (shape 1). Finally, the supertaster

test provided us with insights on the different taste

sensibility of participants and ensures a good distribution of

taster statuses in our study. Overall, we identified 5 nontasters,

11 normal taster (4 tending towards the upper edge

of bitterness sensitivity), and 4 supertasters. These results

are consistent with the known distribution amongst the

general population [3].

STUDY FINDINGS

The description of taste experiences is based on both parts

of the study. We describe the characteristics of taste

experiences across all five tastes along three identified

themes: (1) temporality, (2) affective reactions, and (3)

embodiment (see overview in the supplementary material).

We also discuss the particularities of each individual taste

in order to elucidate the potential design qualities of single

tastes. Each identified theme is represented in a pictorial

visualization of its key characteristics based on the

identified patterns across participants’ verbalizations.

Temporality

While taste experiences have expected elements of

changing intensity (e.g., strong taste, weak taste), the tastes

were also perceived as being mobile (e.g., moving within

the mouth, moving intensities), and occasionally exerted a

physical presence (e.g., building up, eroding, lingering).

These temporal characteristics are intertwined in the

unfolding of the experiences from its initial stimulation

(diachronic structure) and set the stage for the different

taste journeys (synchronic structure). Below, we describe

the different time-intensity profiles of taste experiences.

Taste intensities are generally experienced as being

dynamic and participants’ verbalizations offer a lexicon of

growth and decline. The diachronic nature of taste

experience is also revealed in the immediacy or longevity

of dynamic intensities. For instance, all participants agree

on the immediacy of the sour taste. Such immediacy is

expounded in similes such as ‘a firework in the mouth’, ‘a

punch’, and ‘a flash that hits you’. Yet, despite the

immediacy of this experience, it is short-lasting and decays

rapidly. “When you drink it, you get that bit of a rush. Yes,

it’s basically gone now [P15, sour]. In contrast, other tastes

were described as slowly building up or maintaining

consistent intensities (e.g., high for umami, and low for

salty). Such intensities could be seen to be ‘lingering’,

rather than ‘explosive’, as one participant described it:

“You’ve got this “Whoa” sensation, feels quite strong to

start with. Then it has gone super quick” [P19, sour].

While the dynamics of intensity imply variation (intensity

increasing and decreasing), the vocabulary of movement

animates these changes. Describing the bitter taste, one

participant stated: “I guess it’s not sticky like the first one

[umami]. It’s a bit lively… I feel like it’s moving around”

[P15, bitter]. While certain movements can be attributed to

mouth-feel (e.g., moving left to right across the tongue),

others were externalized (e.g., “I feel it almost into my

sinuses and into the rest of my face” [P14, bitter]). These

expressions were not confined to the temporal

characteristics of taste experiences, but already shed light

on the bodily reactions that can be elicited by tastes.

Movement was also invoked to describe stasis (e.g., ‘stays’)

and repetitive movement (e.g., ‘waves’). “So it is kind of

strong and it also stays. It doesn’t have a peak; it doesn’t

go up and down; it just stays” [P2, umami]. Other tastes

fluctuate rapidly: “Yes, ups and downs, but quite quick.

They’re quite sudden crests and falls…” [P3, sour].

Participants often appealed to similes of physicality in order

to explain their taste experiences (e.g., ‘round’, ‘soft’,

‘heavy’). Such physical experiences are tied to a synchronic

perception of taste. In contrast, the diachronic physicality of

taste experiences is given in the implied and experienced

characteristics of taste as a residual presence (e.g.,

‘lingering’, ‘stays there’): “It just stays in your mouth, so it

kind of keeps developing” [P10, umami] or “it just leaves

its mark in your mouth and doesn’t go” [P7, umami]. Such

experiences are, much like the increasing intensities, those

that ‘build up’, or ‘get a bit stronger”. Such presence is

understood to ‘erode’. Moreover, the implied residual

physicality is associated with experiences of absence. When

tasting sourness, many participants described the

immediate, almost physically imposing intensity followed

by a marked absence. This absence is seen to draw the

taster back into the taste, leaving them wanting more: “it

creates an expectation of sweet flavour, like if you were

biting into a slice of orange or something. … It’s gone now

and actually I’d quite happily have another sip, to be

honest” [P18, sour]. This residual physicality can also be

seen to afford agency to taste experiences, where tastes

‘grab you’, and ‘hit you in the face’. As such, taste

experiences can become reified in exerting influence over

the taster. This can be achieved in the residual physicality

or in absence, for instance, where the marked absence in

sourness is seen as “a forward feeling… It has the feeling of

tartness, your mouth moves forwards” [P14, sour].

Sweetness in contrast is associated with the feeling of

filling the mouth, and when the taste is gone it leaves one

with a kind of stickiness on the teeth.

Figure 2 shows a pictorial representation of the different

types of temporality identified based on the above

descriptions across all five tastes. The intensity is

represented through the thickness of the lines in the bars,

while movement is captured through the frequency of the

lines. Finally, residual physicality as temporal characteristic

is shown through the length of the whole bar. Overall, sour

is the taste delivering the highest intensity, followed by

umami and bitter. Umami presents a high intensity, and is

also characterized by lingering without losing much of its

intensity. Such an extensive residual presence can also be

seen for bitter, however with a lower intensity. Sweet and

salty are also of low intensity and can be characterized by

particular movements. While sweet starts slowly, builds up

and then dies out, salty does not peak at all and is constant

in its perception and moderate in unfolding over time. Sour,

by contrast, is short-lived with a rapid end. Specific to sour

is the sharp beginning followed by the absence of a taste

and the return of it through a forward pulling feeling, which

disappears quickly.

Affective reactions

Affective reactions refer to both the sense of pleasure or

displeasure gained from the taste experience, but also

feelings most often regarding familiarity, such as comfort,

or, by contrast, unfamiliarity, such as surprise and

suspicion. These affective characteristics, to be captured as

pleasant-unpleasant and familiar-unfamiliar, operate not

only as a static attitudinal response to taste experiences

(synchronic structure), but also as evolving characteristics

of the taste experience (diachronic structure).

When sampling the taste stimuli many participants related

their own uncertainty (e.g., I don’t know what to expect).

After one sample, this uncertainty is replaced for familiar

tastes. For unfamiliar tastes, particularly bitter and umami,

the sense of unease pervades and persists. Thus familiarity

produces responses at singular points (e.g., I am/am not

familiar with this), while also producing responses across

time (e.g., I know/do not know what to expect). A recurring

phrase throughout the taste study was “I know what it is, but

I don’t”. While we can at times attribute this to the nature

of the stimuli as water solutions (i.e., those not regularly

experienced by participants), the sentiment expressed also

refers to the lived and felt experiences of the tastes. That is,

while participants on the one hand had the taste ‘on the tip

of their tongue’, those tastes also brought to mind a variety

of known experiences, or, in the absence of known

experiences, feelings of uncertainty or unease. Such

feelings must presumably be associated with evolutionary

causes (considering many bitter foods are poisonous) or in

form of personal memories (e.g., salt, salty water, and the

seaside) and cross-modal experiences (e.g., with color, or

sounds). “If I drink or eat something that leaves that kind of

trace, I always imagine a colour. Glowing…. It’s weird. I

have no idea what this is, but there’s a bitterness that

stays” [P2, bitter]. Participants identified as supertasters

expressed their affective reaction more clearly: “Definitely

bitterness… I don’t like it” [P8, bitter], or “It’s immediately

bitter.… It’s like swallowing medicine” [P18, bitter].

There were few predictable or consistent affective reactions

among participants, and those experienced as pleasurable

by some, were experienced as disgusting or unsettling by

others. The affective response of participants could often be

tied to the participant’s familiarity with the taste. This was

particularly noticeable with umami. Participants who were

familiar with this taste indicated familiarity with savory

Asian cuisine, and could therefore interpret the perceived

taste and experienced it as pleasant. Those who did not eat

Asian cuisine were less familiar with the taste, particularly

in this intensity, and described unease and uncertainty when

tasting it. Such responses also evolved over time, notably

with sweet and sour tastes. While, as mentioned, sour

produced an immediately unpleasant experience, followed

by a refreshingly pleasant experience (e.g., “yes it probably

gets more pleasant as the intensity of the taste dissipates”

[P17, sour]), the taste of sweet was often initially pleasant,

followed by a distinct unpleasantness. This unpleasantness

could be so strongly felt as to produce nausea for some

participants (e.g., “although it’s dying off over time. It’s

quite sickly actually” [P20, sweet]). Such experiences were

tied to the physicality of the taste residing in the mouth, and

were perceived in two extremes for umami, influenced

through the participants’ familiarity/unfamiliarity with this

taste. Participants familiar with this taste perceived the

mouth filling and lingering experiences as comforting

(satisfaction after a full meal), while other participants who

were unfamiliar with it perceived it as disgusting, obtrusive,

and annoying referring to the fact that the taste takes over

control, without the chance to get rid of it quickly.

As with temporality, we created a representation of the

different types affective reactions on the five tastes (see

Figure 3). The pleasant-unpleasant characteristics of the

taste experience are represented through the ‘green’ and

‘red’ colors and in cases of a neutral experience colored as

‘orange’, and finally ‘white’ in case of absence of the taste.

The familiar-unfamiliar characteristics only find an explicit

representation for the umami. The familiarity of the taste

lead to its pleasant perception (upper bar for umami), while

unfamiliarity with the taste was expressed through

unpleasantness (lower bar for umami). Overall, some tastes

are characterized by the change from unpleasant to pleasant

(sour) or the other way around from pleasant to unpleasant

(sweet), while the bitter taste was clearly unpleasant and

salty was described as neutral. For umami, we identified

two separate experiences (participants either love or hate it)

grounded in the familiarity and unfamiliarity of the taste.

Embodiment

Although we would expect food experiences to involve

embodied, textural, responses (such as ‘crunchy’, ‘slimy’),

here each taste stimuli is experienced in the same form (i.e.,

as a colorless and odorless solution), and yet produce varied

embodied responses. Embodiment in relation to the

described diachronic and synchronic taste experiences

refers to the mouth-feel of tastes (how something is felt in

your mouth). Some participants additionally describe whole

body reactions (reactions described beyond the mouth) and

others refer to imagined and disembodied responses

(resulting from the taste stimulation and its associations).

Mouth-feel, referring to the experienced chemical and

physical sensations in the mouth, is frequently used to

describe different characteristics of foods, including coffee,

wine, and textured foods. Such descriptions are offered by

our participants for qualities of texture and viscosity. “It’s

just like a softness, but I guess a little bit more viscosity

even though I’m quite sure it doesn’t have any viscosity. It’s

just sort of the feeling of viscosity, the sweetness and this

cloud is just a bit more mouth feel” [P14, sweet]. The

mouth-feel also relates to a sense of movement, where

tastes evolve in space. Most often these are lateral

movements within the mouth, or commonly tastes are felt to

move backwards. Such experiences can be a feature of the

physical movement of the taste stimuli during the swallow

reflex and also associated with the location of taste

receptors on the tongue. However, in other cases, taste

experiences defied the location of taste receptors and tastes

could be experienced on the teeth, gums, and lips. One

participant goes as far as to describe the absence of mouthfeel:

“I don’t know really. It leaves this numbness in my

mouth like the lemon, but without the initial burst” [P9,

sour]. In addition to the sensations described in mouth,

some participants described bodily reactions that were

opposed to the mouth-feel or isolated taste experiences. “I

think the first part of it, the sour part, is a bit of a shock to

the system. I don’t think you’re expecting it to be like that”

[P16, sour]. Another participant said “I kind of see it from

the moment it enters my mouth and goes down all the way

to my stomach. It’s like I can see where it’s going” [P2,

bitter]. In this sense, participants described tastes as

producing expansive responses, including pleasure, nausea,

and, others including reactions associated with allergy such

as increased body heat (e.g., “If you eat it, it’s like your

body – the heat just changes” [P2, umami]). Feelings of

pleasure were often described as filling, particularly filling

the face or the whole body. A participant describes it as

such: “I feel that my whole face feels pleased with it” [P14,

umami]. Such feelings were not always positive and for

some participants, overwhelming feelings of nausea

accompanied tastes of salt, umami, and sweet. Nausea

could also be experienced in undulating taste experiences –

those taste which were experienced as prone to fluctuations

in intensity, almost mimicking travel or sea sickness.

Participants also described disembodied reactions, which

refer to something experienced that lingers between the

mouth and the body. Rather than experiencing direct bodily

reactions, participants describe an imagined reaction. “It’s

like it’s there but it’s not there” [P2, salty]. Disembodied

reactions could also be seen in expected or caricatured

responses, such as the imagined ‘pucker face’ of the sour

taste. Although few participants actually exhibit such a

reaction, it is an ingrained image of biting into a lemon. “It

feels a little bit, not uncomfortable, but it feels like it makes

you kind of screw you face up a bit” [P11, sour].

Shapes assigned to the overall taste experiences

The usage of the SEI objects (see Figure 4) as a physical

engagement with shapes enriched the description of the

taste experiences. The shapes particularly contributed

descriptors related to the combined temporal, affective, and

embodied experiences of each individual taste. Below, we

summarize the key characteristics and the mapping of the

eight objects for each taste across all participants.

The sweet taste, generally experienced as ‘smooth’ and

‘rounded’, was most reflected in shapes that present

elements of change such as “phases” (shapes 4 and 5) or

have protruding elements (like 7 and 1, or even the halfspiky

shape 2). While typically a pleasant taste, there is a

dynamic modulation of intensity and pleasure in the shapes.

The sour taste produces a ‘sharp’ response and for many is

best characterized by shapes such as 8 or 2. There are,

however, also elements of temporality, a shifting/phasing

associated with shape 4, starting with the big part as an

explosion and then rapidly decaying. The salty taste has a

broad aspect (mapped towards 3 and 6) and a finer

granulated and dynamic experience expressed through the

shape 1. Similar to sweetness and sourness there is a

repeating wave assigned to this taste experience, verbalized

around shapes 4 and 5 though this time associated with an

unpleasant feeling/sickliness as aftertaste. More than other

tastes, salty was associated with a subtlety of the temporal

characteristics, an experience of something moving, not

doing much, but still being there. This made participants

want a shape that they could manipulate (“These [objects]

are kind of too permanent; you’re not able to manipulate

them” [P6]) or something more neutral, such as a flat shape,

or a shape, which can be changed. Despite the fact that the

bitter taste was experienced as unpleasant, the mapping to

the shapes created two distinct experiences. For some

participants, bitter is a spiky but lingering experience

associated with a dull unpleasantness (1, 2, and 7 shapes

selected). For others it is a rounded and smooth taste (these

participants chose shapes 5 and 6), associating it with

medicine (form of pills), which dissolves in the mouth, and

you cannot get rid of it. Similarly to bitter, the mapping for

umami resulted in two distinct experiences. If umami was

experienced as unpleasant, participants tended to describe

the taste as disgusting and chose the shape 8 or 2. In those

cases where umami was perceived as pleasant, participants

described it as a more rounded taste with depth and chose

combinations of the rounded shapes (such as 3 and 1 shape

were used most, and combined with either the 5, 4, or/and 7

shape). This mapping confirms the descriptions of umami

as a full, mouth-filling experience with lots of things to it.

Overall, sweet and sour seem to be the two tastes where

participants show high agreement with respect to mapping

the shapes to taste experiences. Bitter and umami seem to

share some associations and create two different mappings

between shapes and taste experiences, while salty shows a

tendency towards smooth and round shapes, but with the

lack of the ability to change and manipulate the shapes.

Combined representation of the taste experiences

Figure 5 shows the final pictorial representation of all three

characteristics combined for each of the five tastes. The

length of the forms represents the temporal aspects, while

the width captures the mouth-feel. Whole body and

imagined embodiment could not be captured as such, but

are described in detail above. The expression ‘lingering’

was used particularly for sweet, bitter, and umami. When

used for sweet and umami ‘lingering’ is experienced in

combination with a ‘mouth filling’ element (it is filling the

whole mouth), while for bitter there is no filling experience

but it is described as a thin (straight through your mouth to

the back) experience, next to being unpleasant. In the bitter

case, ‘lingering’ thus refers to the residual physicality of

this taste (in the back of your mouth). Sour has an initial

unpleasant taste, dies down quickly, but comes back after a

short absence and leaves one with the feeling of wanting

more. Salty at last is similar to bitter, however with a

shorter life and perceived as less unpleasant. Salty is

perceived as a neutral taste with little consequence.

DISCUSSION AND FUTURE RESEARCH

While sensory researchers and neuroscientists study the

perception of taste and its temporality, their focus is on

quantifying the intensity and perceived changes of intensity

via a wide range of evaluation scales [26] or, in some recent

attempts, by means of time-intensity profiles of fMRI data

 

[19]. Our findings add a semantic level of understanding

underlying the taste experiences, their temporality enhanced

through descriptions of the affective reactions and

embodiment that the five basic tastes provoke.

 

This understanding may be useful when designing for taste

experiences as it provides designers and developers a

vocabulary to talk about taste and the design potentials

related to the different characteristics.

 

First, we discuss the particularities of each taste quality, and then discuss them

with respect to established psychological and behavioral

phenomenon highlighting their design potential for HCI.

design. This claim will be addressed later.

How is taste experienced?

Here we discuss the specific experiences each of the five

basic taste qualities create and can inspire design in HCI.

Sweet: Pleasant but with a bittersweet ending

The sweet taste was consistently described as pleasant,

which turned into something unpleasant. Participants

struggled between the instinctive taste likeability and the

learned taste values and rules (sweet is bad for the teeth),

which can be seen in light of learned associations, discussed

by Schifferstein and Hekkert [32] with respect to taste

experiences of products. Of particular interest with respect

to our findings on crossmodal interactions for sweet

stimulations are the embodied reactions (e.g., “It’s just sort

of the feeling of viscosity, the sweetness and this cloud is

just a bit more mouth feel” [P14]). Such reactions can be

explained through learned associations with sweetened food

and beverages. It is a combination of learned as well as

innate, genetic, and cognitive factors [32]. Sweet sensations

can be used to stimulate and enhance positive experiences,

however, on a limited timescale, as the sweetness is quickly

disappearing leaving one unsatisfied. It’s a pleasant taste

but one that is tinged with a bittersweet ending.

Sour: Unpleasant at first, but with the need for more

In contrast to the sweet taste, the sour taste is described as

short-lived and it often comes as a surprise due to its

explosive and punchy character. This taste overwhelms one

with its rapid appearance and quick decay. It leaves one

with the feeling that there is something missing. Based on

childhood memories, such as for instance of sweet-sour

drops, participants were expecting sweetness, but were left

disappointed, leaving them with the feeling of wanting

more. This phenomena was also observed in the evaluation

of a gustatory gaming interface with children, where sour

was used for negative reinforcement linked to the game

dynamics [17]. Children intentionally failed in the game in

order to get another sour stimulation.

Salty: Not doing much

The salty taste experience was not linked to an extreme

reaction unlike sour, bitter, and umami. This taste is often

described as ‘bland’, ‘discrete’, and ‘just being there and

not doing much’. It is minutely moving around, giving the

feeling of cleansing the mouth, but not being mouth filling

as sweet or umami, and certainty not as unpleasant as bitter,

however lingering almost as long as the bitter taste. The

modesty of saltiness in contrast to all of the other tastes

opens up some interesting questions when looking at the

neuroscience findings. Nakamura’s [19] findings based on

time-intensity fMRI profiles suggest that salty tastes change

more rapidly than do sweet tastes. This is not quite

consistent with how our participants described their

experiences and needs further studies.

Bitter: Unpleasant, not to be experienced again

The perceived intensity of the bitter taste was not the same

for everyone, as confirmed by the supertaster test. While

supertasters felt the experience with more immediacy,

others had to allow the taste to travel to the back of their

mouth to recognize it. After this initial difference, the bitter

experience becomes consistent with respect to its

‘lingering’ features, of ‘staying’ either on the tongue or at

the back of the mouth. Bitter was also described as ‘thin’.

The character of bitter was further revealed through learned

associations referring to ‘biting into a flower’, or

‘medicine’, things you had to take as a child, but after

which you would rather avoid this experience of bitterness.

Bitterness can indicate the presence of toxins [32] and is

found in evolutionary development of humans (e.g., feeling

of suspicion regarding bitter food as poisonous) [7]. It may

be useful for design to make people avoid certain behaviors.

Umami: Like/dislike, but still confusing as a taste

The familiar-unfamiliar characteristics of umami caused

much confusion in our study and participants could not rely

on their intuition. While the ‘like’ or ‘dislike’ of the taste

was decided instantly, the unpicking of the still ‘confusing’

elements of the umami taste was more challenging.

Different word pairs depending on the like/dislike of the

taste were expressed: ‘pleasant–unpleasant’, ‘comforting–

uncomforting’, and ‘liking–disgusting’. We could also see

participants using additional bodily descriptors, in

particular when describing umami as a pleasing experience

(‘face feels pleased’ or ‘body heat changes’). In cases of

dislike, the focus of attention in the verbalizations was the

lingering characteristic of the taste founded in the inability

to get rid of it. In these cases, the residual physicality can be

seen to afford agency. The taste experience becomes reified

in the influence it exerts over the taster. Depending on

personal familiarity/unfamiliarity (which may be defined by

cultural factors) and personal preferences, this taste

experience is quite interesting for design. Umami grabs

one’s attention and initiates a conscious process of

reflection. While judgment on the taste is defined quickly,

the reflective thinking brings to the fore the richness and

variety of the taste. Even when perceived as unpleasant, the

richness is recognized, and linked to the motivation to

remove the taste from the mouth.

How can we design with taste experiences?

Taste experiences can be discussed with respect to their

relevance for design, building on existing psychological and

behavioral phenomenon: rational and intuitive thinking,

anchoring effects, and behavior change.

 

The dual process

theory [14,37], for instance, accounts for two styles of

processing: the intuition based System 1 with associative

reasoning that is fast and automatic with strong emotional

bonds, and reasoning based on System 2 which is slower

and more volatile, being influenced by conscious judgments

and attitudes. Based on our findings, we can see that sweet

is intuitively perceived as pleasant, and bitter as unpleasant,

while sour, salty, and umami cause a reflective process,

confused, for instance, by the surprise appearance and rapid

disappearance of the sour taste. Our findings also give

insights into how to time the presentation of the taste

qualities so that the user can transition from System 1

thinking to System 2 thinking. Figures 2, 3, and 5 can be

used to create the appropriate transitions and time them. For

example, the rapidity of the sour taste experience does not

leave enough time for System 1 to engage with it and

triggers System 2 to reflect on what just happened. Such

reactions when carefully timed can prime users to be more

reason based in their thinking during a productivity task

(e.g., to awaken someone who may be stuck in a loop).

Moreover, an appropriately presented taste can create a

synchronic experience that can lead to stronger cognitive

ease (to make intuitive decisions) or reduce the cognitive

ease to encourage rational thinking. For example, a pleasant

taste can be used to provide achievements across the

workflow, however with the slight hint that there are still

more tasks to do before you are finished (e.g., the slight

unpleasant aftertaste of sweetness). Below, we outline

potential design directions for using taste experiences in

work-related activities and for personal behavior

management. Doing so, we draw on the potential of

different taste qualities and their power to stimulate

intuitive and rational thinking described above.

Managing anchoring effects through taste

A common aspect of everyday activity is interruption. We

are often interrupted by emails, telephone calls, or other

unanticipated events. These interruptions can either be short

(e.g., a quick glance at an email pop-up) or slightly longer

requiring us to change our activity (e.g., a line-manager

walking into your office to ask for something). All these

activities have anchoring effects. In other words, the initial

activity affects our judgments and decision making in the

latter activities. It has also been shown that users often find

it hard to avoid these biases in their judgments [38].

Our study of taste experiences suggests that taste interfaces

can be carefully designed to manage interruptions in such a

way that anchoring effects can be either minimized or

maintained. For example, we know that the salty taste has a

long temporal component with a feeling of “not doing much

but being there”. This taste could be very useful in those

situations where the interruption is small and the user is

expected to return to the initial activity soon. As an

example, when the user notices a pop-up in the bottom left

corner of their desktop (for email or other social media

interruptions) a small salty taste in their mouth which starts

just before the user switches their activity can be useful.

This will prolong their initial experience and remind them

of the initial activity when still checking the social media

page. This could enable smoother transitions back to the

initial activity. Alternatively, however, if the interruption is

a longer activity then it is useful for the user to drop any

priming effect that might transfer to the new activity. In this

case, a sour taste in the mouth would leave the user a quick

sharp taste engaging their rational System 2 but rapidly

decaying helping the user return to a more neutral state by

the time they switch to the new activity. Such management

of anchoring effects is not only useful for productivity

activities but also in other activities, such as gaming. For

example, LOLLio – the taste-based game device described

above [16], currently uses sweet and sour for positive and

negative stimulation during the game play. We suggest that

such a game could be improved based on our framework by

providing fine-grained insights regarding the specific

characteristics of taste experiences, which can be integrated

into the game play. When a person moves between related

levels of a game a continuing taste like bitter or salty is

useful. Whereas when a user is moving to distinct levels or

is performing a side challenge an explosive taste like sour,

sweet, or umami might be useful. The choice of specific

tastes in each category can be tuned by the designer to

create different affective reactions and a sense of agency.

Priming positive behavior through taste

Taste and taste preferences play an important role in our

food choices [24] and food plays a significant role in our

health and wellbeing. The stimulation and manipulation of

taste experiences therefore offers potential to improve a

variety of food behaviors. Using taste stimulation technology

to alter the taste of unpleasant but healthy food is one

obvious route. Expanding the design space for healthy taste

technology, our framework suggests alternative routes.

Taste experiences might be heightened through appeal to

related experiences and sensations. Morphing physical

objects, such as recently suggested shape-changing devices

[29], might also be used to replicate the embodied

expansiveness of the umami taste to stimulate an increased

taste experience for patients receiving chemotherapy who

may suffer from hypogeusia, a decrease in taste sensitivity.

Taste stimulation might also facilitate sustainable food

practices, for instance, linking food waste to taste

experiences. Taste stimuli might thus supplement other

post-actional cues in the effective disturbance of food waste

habits and promote critical reflection. When disposing overripe

bananas, a user might get a sour stimulation for the

waste of food but the immediate reward for waste

separation. Taste stimulation might also reflect various

characteristics of food waste, such as its lengthy impact on

environmental sustainability through the bitter taste. In this

way, the framework for design points to the potential for

taste experiences to be incorporated into timely and

rewarding persuasive messages for positive food behaviour.

CONCLUSIONS

In this paper we presented the results of a user study

exploring the experiential characteristics for each of the five

basic taste qualities. Our analysis of participants’

verbalizations, collected by means of verbal and non-verbal

methods, resulted in three key themes. We provide rich

descriptions on the temporality, affective reactions, and

embodiment of taste experiences. We discuss these themes

for each individual taste elucidating the design potentials

with respect to the specific structure and qualities of sweet,

sour, salty, bitter, and umami tastes.

 

Our findings help to establish a framework for the design of taste experiences in

HCI, enhancing existing technology driven research around

taste, and food interaction design research. Although we do

not provide guidance for the design of a specific interactive

system in this paper, we are convinced that our framework

provides a starting point for designers and developers to

think about design/development potentials for taste in HCI.

Concluding Comment

ACKNOWLEDGMENTS

This work is supported by the EU Marie Curie Action (FP7-

PEOPLE-2010-IEF) and RCUK SiDE (EP/G066019/1). We

wish to thank our study participants and Annika Haas for

the audio-visual support, as well as Katerhine Isbister and

Kristina Höök for providing us with a set of the SEI objects.

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