Attention

The cocktail party effect, the spotlight of attention, the brain networks that direct it, why multitasking fails, and how the brain decides what to ignore.

William James wrote in 1890 that "everyone knows what attention is. It is the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought." Neuroscience has since shown that attention is not one thing but several processes.

Selective attention

In 1953 the British scientist Colin Cherry described the cocktail party effect: in a noisy room you can follow one conversation and tune out others — yet you'll notice if someone across the room says your name. Experiments in which different messages are played to each ear (dichotic listening) showed that unattended information is processed to some degree, raising long debates about when in processing the filter acts.

A spotlight that boosts processing

Attention is often likened to a spotlight. When you attend to a location or feature, neurons in visual cortex that respond to it fire more strongly and more synchronously, while responses to unattended things are suppressed. You can attend to something without moving your eyes (covert attention).

The networks

Two broad brain networks are commonly distinguished. A dorsal attention network (frontal eye fields and intraparietal sulcus) directs attention voluntarily, top-down, according to goals. A ventral attention network, largely right-lateralised (temporoparietal junction and ventral frontal cortex), acts as a circuit breaker when something unexpected and important happens — stimulus-driven, bottom-up attention. The thalamus gates sensory input, and noradrenaline and acetylcholine modulate alertness and focus.

The myth of multitasking

For demanding tasks, the brain mostly switches rather than truly doing two things at once, and each switch carries a cost in time and errors. The "attentional blink" shows that after spotting one target, people often miss a second one appearing within about half a second. Studies have found that using a phone while driving — even hands-free — impairs reaction times and increases the risk of crashes.

When attention differs

Attention problems are central to ADHD, and right-hemisphere strokes can cause neglect of half of space. Attention can be trained to some degree, but evidence that commercial "brain training" games improve everyday attention beyond the trained tasks is weak.