Textbook of Usability

Selective attention is the cognitive ability to focus on one source of information while filtering out others. It is fundamentally a bottleneck: at any moment far more information is available to the senses than the brain can process, so attention must select which streams receive full processing.

Donald Broadbent's filter theory (1958) proposed that attention acts as an early sensory filter, passing one channel for processing and blocking others. Later research by Anne Treisman showed the filter is "leaky" — unattended information is processed to a shallow level, enough to detect highly salient content (like one's own name in an unattended conversation, the "cocktail party effect") but not enough for detailed comprehension.

In interface use, selective attention governs visual search: finding a button, menu item, or piece of information among distractors. Visual search is parallel (fast, size-independent) when the target differs from distractors in a pre-attentive feature, and serial (slow, size-dependent) when the target shares features with distractors.

Design implications:

• Frequently used targets should differ from surroundings in a pre-attentive feature (colour, size, shape)
• Similar items should be grouped so users can locate categories before searching within
• Visual clutter directly competes for attention and slows search
• Important alerts must overcome attentional selectivity through multimodal cues