Behaviour Change

PROPAGANDA FOR CHANGE is a project created by the students of Behaviour Change (ps359) and Professor Thomas Hills @thomhills at the Psychology Department of the University of Warwick. This work was supported by funding from Warwick's Institute for Advanced Teaching and Learning.

Wednesday, November 30, 2016

How fish and chips proved rational decision making is a hoax

“Anyone’s NOT ordering fish and chips?”

It was a typical Friday afternoon when I heard this call from the lady behind the counter as I queued for a plate of fish and chips myself.

While I always knew that fish and chips is a popular dish in the menu, what are odds that given there are ten people in a line but no one is intending to order anything besides fish and chips?

“Word of mouth,” the lady further whispered to herself as she turned the other way.

Bedazzled by her utterance, it was then and there that I thought to myself I must investigate this awesome demand for fish and chips further. 

From a layperson standpoint, I totally agreed with her. Word of mouth as an advertising tool made sense. It should explain a great deal of the picture. At least that was how I got into this fish and chips situation. A senior of mine told me about it once and I was hooked ever since.

However, it would be more amazing if psychology could provide me with better insights. So, I dove deeper. 

Well, perhaps too deep that I found my answer handsomely intersected in fields such as behavioural economics, behaviourism, psychobiology, social psychology, and statistics.

Behavioural Economics
Firstly, I have uncovered that scarcity plays a huge role in increasing the sales of the fish and chips. Research has shown that packaging a product as 'limited edition', or in this case the fish and chips being a ‘Friday-only deal’, it aids the fish and chips to be more desirable (Lynn, 1991). From a customer standpoint, no fish and chips for oneself this week means that one has to wait for the following week.

I have also realized that a very powerful learned association has been established in my mind between the concept of “Friday” as unconditioned stimulus and “fish and chips” as conditioned stimulus (Kimmel, 1966).

From a customer’s perspective, this could translate to an irritating, rather unwelcome voice at the back of our mind every Friday which whispers, “Friday is fish and chips day, go spend that £5.25 (conditioned response),” over and over again, which makes rational decision making almost impossible. So please stop, my dear brain. I want my free will back!

Not only that, just like it has happened to me, I believe that the fish and chips has also invaded the reward system of other people. Yes, even our biology has been invaded by fish and chips disguised as this mischievous idea of, “it is the end of the week. I deserve to be pampered with a nice meal for having such a productive week! Well, what should I have today?” Being a strong extrinsic motivator, the picture of deliciously prepared fish and chips flashes in our mind, rather unwelcomely. 

Social Psychology
Next, since eating fish and chips has become a social norm in the particular setting, it might influence one’s decision on what is the ’right’ thing to eat. By ‘right’, I mean socially acceptable. 

Asch (1951) has found that social conformity (i.e, the tendency of an individual to conform to the norm of the majority) does exist. In this particular case, it’s really hard NOT to choose something besides fish and chips considering everybody is having it.

To test further whether such norm exists, let us do a simple statistical investigation.

Method: Observational study

Time and date: 2.35pm, November 18, 2016.

Results: Out of 28 people who were having something at that time, 20 of them were having fish and chips and the other 8 people were having meals such as salad, sandwich, chips, and jacket potato.

To explore this fish and chips demand phenomenon further, a chi-squared goodness of fit test might also help.

Null Hypothesis: There is no preference for any particular meal

Expected frequency: 14 for both ‘fish and chips’ and ‘non-fish and chips’

Calculated chi-squared value = 5.14

Critical value: 1 df at alpha = .05 is 3.84

Results: Null hypothesis is rejected. There IS preference for a particular meal.

Discussion: Apart from the small sample size, it is safe to conclude that the fish and chips norm does exists. 

Take home message
To conclude, the fish and chips being scarce, perceived as an extrinsic motivator, and a norm in the particular context is enough of an influence to prove that rational decision making is a mere hoax. 

So, taking this idea to a broader concept, the next time people tell you, “I don’t want anyone to influence me, I want to DECIDE it for MYSELF,” just smile to them and hope that others will not prey on their naivety.


Asch, S. E. (1951). Effects of group pressure upon the modification and distortion of judgments. Groups, leadership, and men, 222-236.

Kimmel, H. D. (1966). Inhibition of the unconditioned response in classical conditioning. Psychological Review, 73(3), 232.

Lynn, M. (1991). Scarcity effects on value: A quantitative review of the commodity theory literature. Psychology & Marketing, 8(1), 43-57.

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