Your clutter is spending your attention

Using functional MRI, Kastner and colleagues showed that when multiple stimuli are present simultaneously in the visual field, their cortical representations within the object recognition pathway interact in a competitive, suppressive fashion. Nearby objects do not each get full, parallel processing. They suppress one another.

The crucial finding is what happens when attention is directed to one of them: directing attention to one stimulus counteracts the suppressive influence of nearby stimuli. The authors propose this mechanism may serve to filter out irrelevant information in cluttered visual scenes. This is direct evidence that a cluttered visual field costs your brain resources just to pull signal out of noise, before any task begins.

The Yale team recorded activity in the primary visual cortex while presenting stimuli with and without flanking stimuli, in spatial configurations known to degrade perception non-uniformly. They found that information propagation between cortical layers travels along a structurally stable communication subspace: the pathway does not change. What changes is how efficiently information moves along it.

In the laboratory’s own summary for Yale News, Anirvan Nandy compares it to a phone tree, in which each person calls one other to relay a piece of information until everyone has received it. The order stays the same, the fidelity of the relay does not. As Monika Jadi puts it there, visual clutter in one location would drive information in a particular layer of the primary visual cortex to a lesser extent than clutter in another location. The surroundings of an object measurably change how well your brain carries its signal.

The study tested 663 children aged 7 to 12 (345 with ADHD, 318 without) on a continuous performance test delivered under four conditions: no distractors, pure visual distractors, pure auditory distractors, and combined visual and auditory distractors. The measure was omission errors, the lapses of sustained attention that mark a missed target.

Children with ADHD made more omission errors than their peers in every condition. The asymmetry is the important part: all types of distracting stimuli increased omission errors in the ADHD group, while only combined visual and auditory distractors increased them in the non-ADHD group. The authors’ conclusion is that incorporating distractors in the test improves the ability to distinguish ADHD from non-ADHD children. The implication for a home is straightforward: for an attention-vulnerable brain, environmental distractors are not background.