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Change Blindness

via Unnatural Acts that can improve your thinking

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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:

The Halo Effect

via Unnatural Acts that can improve your thinking

halo_effect 1126The halo effect refers to a bias whereby the perception of a positive trait in a person or product positively influences further judgments about traits of that person or products by the same manufacturer. One of the more common halo effects is the judgment that a good looking person is intelligent and amiable.

There is also a reverse halo effect whereby perception of a negative or undesirable trait in individuals, brands, or other things influences further negative judgments about the traits of that individual, brand, etc. If a person “looks evil” or “looks guilty” you may judge anything he says or does with suspicion; eventually you may feel confident that you have confirmed your first impression with solid evidence when, in fact, your evidence is completely tainted and conditioned by your first impression. The hope that the halo effect will influence a judge or jury is one reason some criminal lawyers might like their clients to be clean-shaven and dressed neatly when they appear at trial.

The phrase was coined by psychologist Edward Thorndike in 1920 to describe the way commanding officers rated their soldiers. He found that officers usually judged their men as being either good or bad “right across the board. There was little mixing of traits; few people were said to be good in one respect but bad in another.”* The old saying that first impressions make lasting impressions is at the heart of the halo effect. If a soldier made a good (or bad) first impression on his commanding officer, that impression would influence the officer’s judgment of future behavior. It is  very unlikely that given a group of soldiers every one of them would be totally good or totally bad at everything, but the evaluations seemed to indicate that this was the case. More likely, however, the earlier perceptions either positively or negatively affected those later perceptions and judgments.

The halo effect seems to ride on the coattails of confirmation bias: once we’ve made a judgment about positive or negative traits, that judgment influences future perceptions so that they confirm our initial judgment.

Some researchers have found evidence that student evaluations of their college instructors are formed and remain stable after only a few minutes or hours in class.  If a student evaluated a teacher highly early on in the course, he or she was likely to rank the teacher highly at the end of the course. Unfortunately, for those teachers who made bad first impressions on the students, their performance over the course of the term would be largely irrelevant to how they would be perceived by their students.

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