5 curious psychological phenomena that affect behaviours

– By Mario Vingerhoets

1. The Bystander Effect


What would you do if you saw a person in need of help? According to the bystander effect your more likely to ignore them if there are other people doing the same as we take our social cues for what is appropriate from the people around us.

The bystander effect occurs when there are two or more witnesses and a victim, but the individuals do not offer to help the victim. The probability of someone helping is inversely related to the number of bystanders. Experiments have found that the presence of others inhibits helping, often by a large margin. There are several variables that help explain why this phenomenon occurs for example: ambiguity, cohesiveness and diffusion of responsibility.[1]

2. The Marshmallow Test

in the 1960’s a series of studies known as the Stanford Marshmallow Tests were conducted, the objective was to analyse the willpower of some children by putting them in a difficult situation. These tests consisted of giving a child one marshmallow and promise him another one if he waits and doesn’t eat the first one. The waiting period is about 15 minutes but the child does not know this. This dilemma is measuring the self-regulation of a person by delaying the gratification. In this theory the children that waited longer for the preferred reward have more chances of being successful in the future.[2]

3. Change Blindness

Can you notice the difference between these two images? do you think you would notice the change if it happened right in front of you in real life?  The psychological phenomenon known as Change blindness is when a change occurs in our range of vision and we are not able to see the difference. One of the reasons these large changes are missed under natural viewing conditions is because they occur simultaneously with a brief visual disruption. It can happen by simply blinking or an involuntary eye movement. In some occasions large changes can also provoke the individual to miss the small, less important, changes.[3]

4. Selective Attention Test

The Selective Attention Test is a similar psychological phenomenon as the change blindness. Human beings have a limited capacity of processing information. That’s why when we hear a speech or concentrate on one particular source of sound we become deaf to any sound coming from elsewhere. The also applies to our vision. For this reason our limited ability to concentrate and to focus on certain subject leaves us blind to the rest of the environment. [4]

What do you see in this video? Many people miss something that happens…
5. The Halo Effect

The halo effect can be found in many circumstances, whether you’re in a classroom or on a train, we can find it in everyday interactions. Its a cognitive bias in which one’s overall impression of somebody can change your judgment about that specific person. In essence the individual attributes of a person can modify our way of treating them; people prejudiced others by thinking that nice individuals tend to have nice attributes and less nice individuals have less nice attributes. Because of this we ended up changing our behavior towards that person it. [5]


1. The Bystander Effect

Garcia, S, Darley, J & Moskowitz, G 2002, “Crowded Minds: The Implicit Bystander Effect”, Journal of personality and social psychology, Vol 83, No. 4, p. 843-853.

2. The Marshmallow Test

Deutsch, M, Coleman, P & Marcus, E September 18, 2006, “The handbook of conflict Resolution: Theory and Practice”, Jossey-Bass, Printed in the United States of America.

3. Change Blindness

O’Regan, J, Rensink, R &Clark, J 1999, “Change-Blindness as a result of mudplashes”, Scientific Correspondence, Nature, Vol 398, p. 34.

4. Selective Attention

Duncan, J. 1984, “Selective attention and the organization of visual information”, Journal of Experimental Psychology: General”, Vol 113, No. 4, p. 501-517.

5. The Halo Effect

Nisbett, R. & De Camp, T. 1977, “The Halo Effect: Evidence for Unconscious Alteration of Judgment”, Journal of Personality and Social Psychology, Vol 35, No. 4, p. 250-256.