Touching Emotions, Smelling Shapes: Exploring Tactile, Olfactory and Emotional Cross-sensory Correspondences in Preschool Aged Children

This study investigates cross-sensory correspondences between touch, smell, and emotion in 26 preschool-aged children (2–4 years) through playful tasks, revealing significant associations and underlying strategies that inform design guidelines and methods for understanding early childhood sensory cognition.

The Gist

Imagine your brain is like a super-smart translator. Usually, it's great at translating what you see into what you hear (like knowing a siren means "stop"). But what about translating what you smell into what you feel or touch?

This paper is a fun, scientific adventure that asks: Do little kids (ages 2 to 4) have their own secret translator for smells, shapes, and feelings?

Here is the story of what the researchers found, explained simply.

🧪 The Experiment: A Magic Box Adventure

The researchers didn't sit 2-year-olds down with a clipboard and ask, "What does this smell like?" That would be too boring and confusing! Instead, they turned the study into a story.

• The Setup: They built a "Magic Box" with a hole in it. Kids couldn't see inside, but they could reach in and touch three special 3D shapes:
  1. A Spiky ball (like a sea urchin).
  2. A Round ball (smooth and bouncy).
  3. A Cylinder (like a short tube).
• The Mission: The kids were told these shapes were characters named "Kiki" and "Bouba." They had to guess which name fit which shape just by feeling it.
• The Smell Test: Then, they smelled three things: Lemon, Vanilla, and Air (nothing).
• The Feeling Test: Finally, they had to decide if each shape or smell belonged to an "Excited" village or a "Calm" village.

🎨 The Big Discoveries

1. The "Kiki" and "Bouba" Effect is Real (Even for Toddlers!)

You might have heard of the "Bouba-Kiki" effect. It's a famous trick where almost everyone, no matter their language, thinks a spiky shape looks like the name "Kiki" (because it sounds sharp) and a round shape looks like "Bouba" (because it sounds soft).

• The Finding: Even the 2-to-4-year-olds got this right! They felt the Spiky shape and said, "That's Kiki!" They felt the Round shape and said, "That's Bouba!"
• The Twist: Some kids invented their own names (like "Star" or "Grape"), but the sounds they picked still followed the same rule: sharp sounds for spiky things, soft sounds for round things.

2. Smells Have Personalities

The kids were surprisingly good at matching smells to feelings.

• Lemon (sharp, zesty) = Excited (like jumping up and down!).
• Vanilla (sweet, soft) = Calm (like taking a nap).
• Air (nothing) = Neither.
• The Connection: The kids also matched the smells to the shapes! Lemon went with the Spiky shape, and Vanilla went with the Round shape. It seems their brains naturally link "sharp/zesty" with "spiky" and "sweet/soft" with "round."

3. The "Friendship" Surprise (Where Kids Differ from Adults)

This is the most interesting part. When adults look at a spiky shape, they usually think, "Ouch, that's dangerous or exciting!" But when the kids looked at the Spiky shape, some of them said it was Calm.

• Why? The kids explained it using friendship. One child said the Spiky shape was calm because "it has no friends" (so it's just sitting there quietly). The Round shape was excited because "it has friends!"
• The Lesson: Adults use logic (spiky = sharp = dangerous). Toddlers use imagination and social stories (spiky = lonely = quiet). Their brains are still learning how to connect shapes to big feelings.

🧠 How Did the Kids Explain It?

When asked why they made these choices, the kids didn't use big words. They used two main tools:

1. "I've seen this before!" (Familiar Experience): They compared the round shape to grapes or bubbles. They compared the lemon smell to Play-Doh or strawberries. They anchored new things to things they already knew.
2. "It feels like..." (Sensory Features): They used simple words like "sharp," "smooth," or "hard."

💡 Why Does This Matter? (The Takeaway)

This study is like a map for designers who want to build toys, apps, or tools for little kids.

• Don't assume kids think like adults. If you make a "calm" app for a child, don't just use a soft, round shape and a lemon scent (which adults might find relaxing). To a kid, lemon might mean "excited!"
• Use Stories. Kids learn best when information is wrapped in a story or a game, not a test.
• Smell is a Superpower. We often ignore smell in technology, but this study shows kids can use smells to understand emotions and shapes. Imagine a toy that smells like vanilla when a child is feeling calm, or lemon when they are playing!

In short: Little kids have a magical, intuitive way of connecting what they touch, what they smell, and how they feel. They might not have the words to explain it perfectly, but their brains are already drawing the lines between the world's senses.

Technical Summary

Here is a detailed technical summary of the paper "Touching Emotions, Smelling Shapes: Exploring Tactile, Olfactory and Emotional Cross-sensory Correspondences in Preschool Aged Children."

1. Problem Statement

While multisensory interaction is central to human perception and learning, most digital technologies focus primarily on visual, auditory, and tactile modalities, neglecting chemical senses (smell and taste). This is particularly critical in Child-Computer Interaction (CCI) for preschoolers (ages 2–4), a developmental window where sensory integration is rapidly maturing.

Existing research on cross-sensory correspondences (systematic mappings between senses, e.g., the Bouba-Kiki effect) has largely focused on older children (10–17 years) and adults. There is a significant gap in understanding:

• How preschoolers map olfaction (smell), tactile (touch), and emotion to one another.
• The specific cognitive strategies (association strategies) young children use to justify these cross-modal connections.
• How to design technologies that leverage these early-developing correspondences for emotional expression and communication.

2. Methodology

The authors conducted a controlled, story-based study with 26 preschool children (ages 2–4.5 years; 16 female, 10 male).

Experimental Apparatus & Stimuli

• Tactile Stimuli: Three 3D-printed, translucent resin shapes with identical volume (~65mL) and weight (80g) to control for haptic cues:
  • Spiky: Angular, sharp edges.
  • Round: Smooth, spherical.
  • Cylinder: Neutral, smooth.
• Olfactory Stimuli: Three scents dispensed via a Hynt scent-dispensing machine:
  • Lemon: Citrus, sharp.
  • Vanilla: Sweet, soft.
  • Air: Neutral control.
• Emotional Stimuli: Three emotional states represented as "villages": Excited, Calm, and Neither.

Procedure

To accommodate the cognitive and attentional limitations of 2–4 year olds, the study utilized a narrative framework rather than abstract rating scales (like the Self-Assessment Manikin).

1. Storytelling: Children were told a story where the shapes were anthropomorphic characters living in different emotional villages.
2. Tasks:
   • Naming: Children felt a shape (hidden in a box) and named it "Bouba," "Kiki," or created their own name.
   • Tactile-Emotion: Assigned an emotion (Excited/Calm/Neither) to each shape.
   • Olfactory-Emotion: Assigned an emotion to each scent.
   • Tactile-Olfactory: Matched scents to shapes (framed as "soaps" for the characters).
3. Data Collection: Sessions were audio/video recorded. Researchers collected both the choices made and the verbal reasoning (association strategies) provided by the children.

Analysis

• Statistical: Pearson's Chi-square tests and standardized residual analysis were used to determine significant associations between stimuli.
• Qualitative: Deductive coding was applied to identify Association Strategies (based on prior work by Roberts-Morgan et al.) used by children to justify their choices (e.g., Familiar Experience, Sensory Features, Valence, Personal Connection).

3. Key Results

A. Cross-Sensory Correspondences

1. Tactile-Linguistic (Bouba-Kiki Effect):

   • Significant Association: Strong correlation found between shape and name.
   • Spiky shapes were overwhelmingly associated with "Kiki".
   • Round shapes were associated with "Bouba".
   • Note: Even when children invented new names, the phonetics followed the pattern (e.g., "Spiky" used hard consonants like /k/, /t/; "Ball" used soft consonants like /b/, /l/).

2. Olfactory-Emotion:

   • Significant Association: Clear mapping between scent and emotion.
   • Lemon $\rightarrow$ Excited (High arousal).
   • Vanilla $\rightarrow$ Calm (Low arousal).
   • This aligns with findings in older children and adults.

3. Tactile-Olfactory:

   • Significant Association:
   • Spiky $\rightarrow$ Lemon.
   • Round $\rightarrow$ Vanilla.
   • Cylinder $\rightarrow$ Air (Neutral).

4. Tactile-Emotion (The Divergence):

   • No Significant Association: Unlike adults (who link spiky shapes to high arousal/excitement), preschoolers did not show a statistically significant link between shape and emotion.
   • Observation: Some children even inverted the adult pattern (associating "Spiky" with "Calm" and "Round" with "Excited").
   • Reasoning: Children often used social reasoning (e.g., "Spiky has no friends" = calm/sad; "Round has friends" = excited) rather than physical properties to explain emotions.

B. Association Strategies

• Familiar Experience: The dominant strategy (42.5% for touch, 69.6% for smell). Children linked stimuli to concrete objects (e.g., "grapes," "Play-Doh," "strawberries").
• Sensory Features: Used frequently for tactile stimuli ("sharp," "smooth") but rarely for olfactory stimuli. This suggests a linguistic gap in describing smells compared to touch.
• Valence: Used often for scents ("I like it," "I don't like it").
• Social/Anthropomorphic: Children frequently personified the shapes to explain emotional states, indicating that emotional reasoning at this age is grounded in social narratives rather than abstract sensory properties.

4. Key Contributions

1. Empirical Evidence: Provided the first systematic data on smell-touch-emotion correspondences in children aged 2–4, confirming that the Bouba-Kiki effect and smell-emotion mappings exist early, while tactile-emotion mappings are still developing.
2. Methodological Innovation: Developed and validated a story-based, child-centered protocol for probing cross-sensory cognition in preschoolers. This approach successfully bypassed the need for abstract reasoning required by standard adult psychometric tools.
3. Association Strategy Analysis: Identified that preschoolers rely heavily on concrete, lived experiences and social narratives rather than abstract metaphors when explaining cross-sensory links.
4. Design Guidelines: Established principles for designing cross-sensory technologies for young children, emphasizing the use of familiar objects, exaggerated sensory qualities, and alignment with early-developing correspondences (e.g., lemon = excitement).

5. Significance and Implications

• Theoretical: The study suggests that while some cross-sensory mappings (smell-emotion, shape-name) are robust and emerge early, others (shape-emotion) are fluid and heavily influenced by social development and narrative framing in early childhood.
• Practical (HCI Design):
  • Emotional Communication: Technologies can use scents (lemon/vanilla) as reliable proxies for emotional states (excited/calm) for non-verbal or pre-verbal children.
  • Inclusivity: Story-based interfaces can scaffold emotional expression for children who struggle to articulate feelings verbally.
  • Avoiding Adult Bias: Designers must avoid assuming adult scent-emotion associations (e.g., assuming lemon is always "refreshing/calm") and instead align with the child's intuitive mappings (lemon = excitement).
• Future Directions: The methodology opens the door for studying other sensory domains (taste, audition) in early childhood and developing inclusive tools for children with diverse communicative abilities.