Life without left

A psychologist was walking across the hospital grounds when she saw one of her patients walk by.

“Hi, John,” she said.

John didn’t seem to react to this.

“Hi, John,” she repeated. “It’s me.”

John looked at her and said, “Ah, I recognise your voice.”

The psychologist explained that they see each other every week at the hospital.

“Oh yes,” John responded. “I will remember next time: long hair, Canadian.”

The patient had prosopagnosia, the inability to recognise faces.

At that point Anne Aimola Davies decided to change the course of her career.

“I returned to university to do graduate studies, and I have never looked back.”

She went from being a registered psychologist to a clinical neuropsychologist, with a research interest in visual attention.

Associate Professor Aimola Davies is now at the ANU Research School of Psychology, home to diverse research in human cognition and perception. The focus of her work is unilateral visuospatial neglect. Her patients have had a right-hemisphere stroke, and have lost the ability to orient attention to the left side of their world.

Self-portrait by a patient suffering from unilateral visuospatial neglect.

It seems like a strange thought: what is life like without left?

Her patients have an intact occipital lobe—the area in the brain responsible for vision—but they have lost awareness of the left side. When asked to describe a street view, they mention the buildings only on the right side; when they have slices of pizza on their plate, they might notice only the slices on the right half.

“It isn’t just the left of space, it’s also the left of an object and things that clearly have a left and right side,” Associate Professor Aimola Davies says. Together with one of her PhD students she found, for example, that neglect can lead to issues in noticing the left side of the Norwegian letter Æ. A person with unilateral visuospatial neglect sees it as an E.

The invisible gorilla experiment

You might have heard about the invisible gorilla experiment. In this experiment, participants watch a video of people playing basketball and are asked to count the passes between the players. Most participants fail to report the person in a gorilla suit who walks into the middle of the players at one point. This is called inattentional blindness: when healthy people fail to notice something directly in front of them because their attention is engaged by a task.

Something similar occurs in an experiment where people look for farm animals on a computer screen and fail to report that a chair also appeared.

“If you’re looking for animals, your brain is gathering up information about animals, and you’re prepared to see animals. There is no way you don’t see that chair, but your attention is on a semantic category: animals. The other information doesn’t seem to be processed to the level of consciousness.”

This kind of inattentional blindness is about shifting attention from one category to another, while unilateral visuospatial neglect is about shifting attention in space. Associate Professor Aimola Davies’ research at ANU looks at how the relationship between the two could lead to improved rehabilitation for people who have had a right-hemisphere stroke. Studying inattentional blindness reveals, for example, that it’s not simply an issue of left or right; it’s about high-level processing of categorical information in the brain.

Neglect can lead to issues in everyday life. Think about not being able to make a left-hand turn or leaving half of your food on the plate. Associate Professor Aimola Davies' research could help these patients perceive a whole world, half of which is currently hiding in plain sight.