A1.1.7 Psychological Factors

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The Five Senses as Design Tools

Smell (Olfaction)

How it is used in design:

The olfactory system is unique among the senses in that it has a direct neural pathway to the limbic system — the brain's emotional and memory centre. This means smell triggers emotional and associative responses faster and more powerfully than any other sense.

Designers exploit this connection deliberately.

Evidence and examples:

Sound (Audition / Acoustics)

How it is used in design:

Sound design in product development operates across two distinct domains:

1. Functional sound — auditory feedback that communicates operational status

2. Emotional sound — engineered acoustic signatures that shape brand perception and emotional response

Functional Sound Design:

• The click of a well-engineered mechanical keyboard communicates tactile precision and reliability through acoustic feedback

• The thud of a luxury car door closing is actively engineered — Rolls-Royce spent years developing the precise acoustic signature of their door closure. The sound communicates solidity, safety, and craftsmanship

• Medical device alarms are tuned to specific frequency ranges to maximise detection (targeting the 2–5 kHz range of peak human auditory sensitivity — note: this overlaps with physiological factors)

Emotional Sound Design:

• Harley-Davidson attempted to trademark their V-twin exhaust note — recognising it as a core brand asset

• Porsche employs acoustic engineers specifically to tune exhaust notes to reinforce performance expectations

• Intel's four-note sonic logo (bong) is one of the most recognised sound brands globally — designed to communicate innovation and reliability in under 3 seconds

• Dyson vacuum cleaners: the high-frequency motor note was engineered to sound powerful — research showed users perceived higher suction power from products with a higher-pitched motor sound, regardless of actual airflow performance

Touch (Tactile / Haptic Sensation)

How it is used in design

Touch encompasses both texture (surface quality) and temperature (thermal perception). Together these constitute some of the most powerful psychological signals of product quality and appropriateness.

Texture:

Apple's transition from plastic to aluminium unibody construction in MacBooks was not driven by structural necessity alone — it was a deliberate tactile signal of premium positioning. The cool, dense, smooth surface of aluminium under fingertips communicates a set of values (precision, solidity, investment) that plastic cannot replicate, regardless of structural equivalence.

Temperature:

Materials conduct heat differently. A product made of metal at room temperature feels cold to touch. The same product in polymer feels warmer. This is not a temperature difference in the product — it is a psychological interpretation arising from different thermal conductivity values.

This is exploited in:

• Medical devices (stethoscopes warmed before patient contact — reducing anxiety)

• Food and beverage product design (ceramic mugs retain warmth, reinforcing comfort associations)

• Automotive interior design (leather steering wheels warmed to prevent the cold-touch aversion response)

Haptic Feedback (Digital Products):

Modern touchscreen devices use vibration actuators (haptic engines) to simulate tactile feedback — the psychological click of a virtual button. Apple's Taptic Engine generates precise linear vibrations that simulate mechanical key travel. Research shows users perceive touch-screen keyboards with haptic feedback as more accurate and satisfying, even when typing performance is statistically equivalent.

Taste (Gustation)

How it is used in design:

Taste is the most constrained of the five senses in industrial design — it is relevant only where the product makes direct oral contact or is consumed. However, within these domains, taste psychology is a primary design driver.

Food and Beverage Product Design

Taste is not purely chemical — it is profoundly psychological and multisensory. Research by Charles Spence (Oxford, Crossmodal Research Laboratory) consistently demonstrates:

• The colour of a container influences perceived taste (orange juice in a blue bottle is rated less sweet)

• The weight of cutlery influences perceived food quality (heavier fork = higher rated meal)

• Ambient sound affects taste (low frequency sound enhances bitterness; high frequency enhances sweetness — airlines must account for this at altitude)

• The shape of a cup influences coffee flavour perception (angular cup = more bitter;

Pharmaceutical and Healthcare Product Design

Taste masking is a major pharmaceutical design challenge. Medication that tastes bitter is less likely to be taken consistently, directly affecting health outcomes. Design solutions include:

• Polymer film coating on tablets (neutral or sweet taste)

• Flavoured paediatric liquid medicines (reducing compliance resistance in children)

• Sublingual wafer design (dissolving strips engineered for neutral-to-pleasant taste)

Packaging and Container Design

Materials used in food contact products must be taste-neutral — they must not impart flavour to contents. Polypropylene, stainless steel and glass are preferred for this reason. Taste contamination from packaging (off-flavours from plasticisers) is a failure of psychology factor consideration — the product literally tastes wrong, regardless of food quality.

Vision (Visual Psychology)

Colour Psychology

Colour communicates before form, before label, before function. The psychological associations of colour are both universal (arising from evolutionary conditioning) and culturally specific:

Form Psychology (Gestalt Principles):

The Gestalt principles describe how humans psychologically organise visual information:

• Proximity: Elements close together are perceived as a group → informs product control clustering

• Similarity: Similar elements are perceived as related → informs visual hierarchy in interfaces

• Continuity: The eye follows smooth lines → informs product form flow and visual direction

• Closure: Incomplete shapes are mentally completed → informs logo and icon design

• Figure/Ground: Objects are perceived against a background → informs contrast and legibility design

Aesthetic Responses:

Research in neuroaesthetics (Semir Zeki, UCL) demonstrates that visually beautiful products activate the same reward pathways as music and love. This has direct commercial implications:

• The perceived value of an identically performing product is higher when its visual form is judged aesthetically superior

• Form language (organic curves vs angular geometry) triggers psychological associations: organic = approachable, natural, comfortable; angular = precision, performance, technical authority

• Surface finish (matte vs gloss) communicates: matte = understated premium, professional; gloss = energy, boldness, accessibility

Case Study

Dyson Supersonic Hair Dryer

• Sound: Motor moved into handle — eliminates high-frequency motor noise; perceived as quieter AND more premium

• Touch: Balanced weight distribution (motor mass in handle not head) — feels more controllable and less fatiguing

• Vision: Visible internal mechanism through the circular air amplifier — transparency communicates innovation and function confidence

• Temperature: Precision heat control eliminates the burning smell of overheated hair — smell as a negative psychology factor removed by design

Summary

Key Vocabulary

Practice Questions

Question 1 (4 marks)

Question 2 (6 marks)

Question 3 (3 marks)

Sources

IB Design Technology Guide (First Assessment 2027)

Spence, C. — On the psychological impact of food colour (2015, Flavour journal)

Spangenberg, E., Crowley, A., Henderson, P. — Improving the store environment: do olfactory cues affect evaluations? (1996, Journal of Marketing)

Lindstrom, M. — Brand Sense (2005, Kogan Page)

Chapman, J. — Emotionally Durable Design (2005, Earthscan)

Zeki, S. — Inner Vision: An Exploration of Art and the Brain (1999, Oxford University Press)

Spence, C. & Shankar, M. — The influence of auditory cues on the perception of, and responses to, food and drink (2010)