Attention and Selective Attention

Your eyes take in about 10 million bits of information per second. Your conscious attention processes about 40. The difference is what this section is about: attention is the ferocious filter that decides which tiny fraction of the sensory flood actually reaches awareness.

Types of Attention

• Selective attention. Focusing on one stimulus while ignoring others. Following one voice at a party.
• Divided attention. Trying to handle multiple attention-demanding tasks simultaneously. Driving while texting.
• Sustained (directed) attention. Maintaining focus on a single task over time. Reading this page.
• Alternating attention. Switching between tasks, one at a time.

Attention is a limited resource. Doing two demanding things at once means either rapidly switching between them (not actually doing both simultaneously) or doing both poorly. The popular concept of “multitasking” is mostly task-switching, and it comes with a cost: each switch takes time and effort.

Inattentional Blindness and Change Blindness

Two classic failures of attention:

• Inattentional blindness - failing to see an unexpected stimulus that is right in your visual field because your attention is focused elsewhere. The famous “invisible gorilla” experiment: viewers counting basketball passes fail to notice a person in a gorilla suit walking through the scene.
• Change blindness - failing to notice changes between a previous and current state of a scene. Classic demonstration: a person asking directions from a stranger is briefly blocked, swapped for a different person, and the stranger doesn’t notice.

Both phenomena prove that perception is not a passive video recording - it is a selective reconstruction gated by attention.

The Cocktail Party Effect

Cocktail party effect: the ability to focus on one voice in a noisy crowd while still detecting salient signals (like your own name) in unattended streams. This observation drove decades of theories about how selective attention works.

Theories of Selective Attention

The classic dichotic listening experiment plays one message into each ear and asks the subject to repeat (shadow) the message in one ear. What happens to the unattended message?

Broadbent’s Early Selection (1958)

All sensory information enters a sensory buffer. A selective filter operates immediately, based on physical features (pitch, location, voice). Only one message gets passed on to perceptual analysis and meaning extraction. The unattended message is blocked.

Pathway: sensory register → selective filter → perceptual processing → consciousness.

Problem: If the unattended message is truly blocked, how do you hear your name in the other ear (cocktail party effect)?

Deutsch and Deutsch’s Late Selection

Everything gets processed for meaning. The filter comes after perception; it decides what reaches consciousness.

Pathway: sensory register → perceptual processing → selective filter → consciousness.

Problem: This is computationally expensive - processing everything for meaning seems wasteful.

Treisman’s Attenuation Theory

A middle ground. Instead of a hard filter, there is an attenuator that weakens (not eliminates) the unattended stream. All streams still reach perception, but the attended one is loud and the others are whispered. Important words (your name, the word “fire”) can still break through if loud enough relative to their attenuated volume.

Pathway: sensory register → attenuator → perceptual processing → consciousness.

Treisman’s theory handles the cocktail party effect elegantly and is the most widely cited of the three on the MCAT.

Spotlight and Resource Models of Attention

• Spotlight model. Attention is like a movable spotlight that illuminates one small area of the perceptual field at a time. You can redirect it, but only one area is “lit” at a time.
• Resource model. Attention is a limited pool of cognitive resources. Tasks consume resources; when demand exceeds supply, performance drops. Explains why doing two demanding things at once is worse than doing either alone, even when they use different sensory modalities.

Multitasking: Task Similarity, Difficulty, Practice

Three factors determine how well you can do two things at once:

• Task similarity. Two tasks that use the same cognitive system (both verbal, both visual) interfere more than tasks using different systems. You can listen to classical music while writing a paper; you cannot listen to someone’s speech while writing.
• Task difficulty. Harder tasks demand more attention. Driving in heavy traffic leaves no room for a phone call; driving on an empty highway leaves plenty.
• Practice. Skilled tasks become automatic and demand little attention. Adult drivers can hold a conversation while driving, something impossible for new drivers. The transition from controlled to automatic processing is the core benefit of practice.