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Human Perception

Human perception is the process of identifying, interpreting and attaching meaning to what we experience through our senses. Although we rely on all of our senses - vision, hearing, touch, smell, taste and kinaesthesia (our ability to feel the movements of our limbs and body) - most research has been on visual perception, and to a lesser extent auditory perception. While perception is driven by sensory input (bottom-up processing) it is also driven by long-term memory: how previous experiences, expectations and culture can influence what we detect in the world around us (top-down processing).

Why is understanding perception important?

In terms of HCI and design, we need to understand how people perceive shapes and colours (visual perception), sounds (audio perception), and temperature and pressure (haptic perception) to allow for us to make key assumptions about an interface before any user tests have been performed. Understanding perception also allows us to better interpret the responses users have to an interface.

Visual Perception

Vision is the dominant sense for the acquisition of information from our environment. Size/Depth, Brightness and Colour are the three main aspects of visual perception that are integral to design. An example of how visual perception impacts on design is how words that are in bold font are often perceived as being more important than those that are not. Another example would be how red and yellow are colours that are often perceived to convey a warning or danger. The use of colour is also an indication of how culture influences perception: in China, red is associated with good luck rather than danger.

Auditory Perception

Although visual perception receives the most attention in literature and research, auditory perception is also invaluable. Think about all the things we would misunderstand or overlook if there were no auditory cue to alert us to their presence or status. Usage of sound in interface design includes the following:

• Attention attraction: a siren is perceived by users as an alert that something is wrong or needs attention.
• Status Information: soft background sounds from a computer support the assumption that an operation (e.g. file download) is progressing.
• Confirmation: unique sounds attributed to unique actions inform whether or not an action was performed successfully (e.g. the thudding chime of an error message in MS Windows, or the ‘click’ sound associated with the pressing of a button).

Haptic Perception

Less important than auditory or visual perception for interface design, but still important. Simple tasks like picking up objects are made difficult without haptic feedback about how hot or cold they are, or how much pressure they are generating. Touch is also an important source of feedback within design:

• Pressing buttons (the pressure needed to press a button and ).
• Using a keyboard (dots on the ‘f’ and ‘j’ keys to find the home-row keys for touch typing).
• Handheld device (sensitivity of jog dials to scroll through options on an mp3 player).

For users with other senses impaired, haptic input and output from an interface is an important source of information (e.g. Braille).

Finally, understanding auditory and visual perception, coupled with experience about user expectations, is also fundamental to performing competitor reviews. Comparing across various providers of similar interfaces, systems and services would not be possible without an understanding of how all people fundamentally interpret what they see and hear.

Jargon Buster

Perception
The acquisition and interpretation of stimuli in our environment through our senses.

Bottom-up processing
Often referred to as ‘object recognition’, it is how humans interpret individual stimuli and bring them together to form perceptions about our world/environment. Template Matching Theory, Feature Analysis, and Prototype Matching are the 3 theories most commonly associated with bottom-up processing and perception.

Top-down processing
How previous experiences, expectations and culture influence how we perceive the world around us. In the included example (Fig. 1), we read ‘the cat’ even though the same character is used for the ‘h’ in ‘the’ and the ‘a’ in ‘cat’. Being in between two sets of characters that are distinctly letters, we expect that we are therefore looking at 2 words. To meet our expectations, our brains fill in the visual gaps so what we see makes sense.

Kinesthetics
The ability to feel the movement of our limbs and body, i.e. being aware of our positioning in space.

Haptic
Related to or proceeding from the sense of touch. Pressure and temperature are both components of haptic feedback.

Further Reading

Federal Aviation Administration (FAA) Human Factors Awareness Course

Ratey, H. Users guide to a Brain: Perception, Attention and the Four Theaters of the Brain. 2002

Wickens, C. Engineering Psychology and Human Performance. 1992