Tag Archives: Visual field

Change Blindness

via Unnatural Acts that can improve your thinking

This image is changing.

Do you see how this image is changing?
More here

Change blindness is the failure to detect non-trivial changes in the visual field. The failure to see things changing right before your eyes may seem like a design fault, but it is actually a sign of evolutionary efficiency.

Examples may be seen by clicking  here, here, and here.

The term ‘change blindness’ was introduced by Ronald Rensink in 1997, although research in this area had been going on for many years. Experiments have shown that dramatic changes in the visual field often go unnoticed whether they are brought in gradually, flickered in and out, or abruptly brought in and out at various time intervals. The implication seems to be that the brain requires few details for our visual representations; the brain doesn’t store dozens of details to which it can compare changes (Simons and Levin: 1998). The brain is not a video recorder and it is not constantly processing all the sense data available to it but is inattentive to much of that data, at least on a conscious level.

Change detection in films is notoriously poor when the change occurs during a cut or pan, as demonstrated by the color-changing card trick video and a number of other videos where a different actor appears after a cut, without the change being noticed by most viewers. Some experiments have shown that a person may be talking to someone (behind a counter, for example) who leaves (bends down behind the counter or exits the room) and is replaced by a different person, without the change being noticed.

Apparently, change blindness is due to the efficient nature of our evolved visual processing system, but it also opens the door to being deceived, much to the delight of magicians and sleight-of-hand con artists.


More examples of change blindness:

More Inattentional Blindness

via NeuroLogica Blog

First, take the challenge presented in this video:

This is a demonstration of inattentional blindness (or attentional blindness) – when we are focused on one task this interferes with our processing of other information. This is exactly why you should not text while driving, or even talk on the phone while driving.

The cause of this is conceptually simple: our brains have limited processing power, more limited than we would like to think. When we use some of that processing power for one task it is not available for other tasks, even basic tasks like seeing obvious things right in front of our eyes. This concept is called load theory, and researchers have documented numerous ways in which it manifests. A related concept is that of interference – when we perform one task it reduces our performance on other tasks. In fact, the act of multitasking itself causes interference because multitasking requires processing power (it takes brain power to switch among more than one task)  which is taken away from each task.

Interference is probably greater for tasks that are vying for the same parts of the brain. It seems that different areas or modules in the brain participate in multiple networks engaging in different tasks. Placing a processing load on one module for different tasks causes significant interference. Some modules participate is very basic functions, like perception, attention, and memory, and therefore become overloaded very easily.

A recent study has demonstrated a new aspect of this phenomenon. Up to now research demonstrating inattentional blindness has used visual clutter to distract from seeing the target – following the basketball interfered with the ability to detect the gorilla. The new research creates the same effect without visual clutter but instead using visual memory:

Participants in the study were given a visual memory task to complete while the researchers looked at the activity in their brains using functional magnetic resonance imaging. The findings revealed that while the participants were occupied with remembering an image they had just been shown, they failed to notice a flash of light that they were asked to detect, even though there was nothing else in their visual field at the time.

This research suggests that remembering an image uses similar resources to seeing an image – that visual memory and perception are similar in terms of the brain resources that are used (which is in line with previous research).

Assuming the results of this study are reproducible, it extends the implications of inattentional blindness. Not only is texting or using a cell phone distracting while driving, the researchers suggest that trying to visualize directions or remember that image on a navigational GPS system can cause interference and reduce a driver’s ability to detect obstacles in front of them.

There are a few take-home messages from this line of research I would like to emphasize.

MORE . . .

%d bloggers like this: