Do fizzy drinks cause aggression?

Posted on January 17, 2012


Image: Wikipedia

Dateline: 24 October 2011 // Posted by: Stephen Smith

Source: Evening Herald, The Telegraph, Irish Independent

Story: “Just one can of a fizzy drink a day makes teens more aggressive”

Summary: A new study conducted by researchers in the United States has revealed that the consumption of five cans or more of non-diet carbonated soda drinks is linked with an increased likelihood of teens engaging in acts of violence or carrying weapons on their person. The research, which was published in the online journal, Injury Prevention, involved almost 2,000 participants in Boston aged between 14-18 years of age self-reporting regarding their fizzy drink consumption and the levels of violent acts which they engage in.

The study was conducted using a sample mainly comprising of teenagers from ethnic minorities with poor backgrounds with black or multi-racial Hispanic and Asian participants making up 90% of the group. Participants who had consumed five or more cans of soda in the past week were categorised as being in the high consumption bracket with those who had consumed four or less cans making up the low consumption group.

On the whole, regular consumption of fizzy beverages was linked with a 9-15% increased probability of engaging in violent actions. Also, of participants who drank no more than one can per week, 23% reported carrying a knife or gun and 15% had been violent toward their partner as compared with those participants who had consumed 14 or more cans, 43% of whom reported carrying a weapon and 27% of whom reported being physically abusive towards their partner.

Why is this PseudoNews? This study and the manner in which it is spoken about by the researchers is decidedly flawed in this instance as it seems to infer a causation between the two variable without factoring in some of the drawbacks and caveats to making such claims. One of the researchers, Dr Solnick, makes a statement that “the drinking more of the soft drinks is leading to more violence”, an assertion which suggests that causality for the inflated rates of violence in the participants can be directly attributed to excessive soft drink consumption. However, the results put forward by this study lend no credence to her inferring that a causal relationship exists as the data should be treated with a far greater level of tentativeness and caution. It is widely known that correlation does not mean causation but this researcher has been far too rash in her treatment of the results.

Also notable are the numerous weaknesses present in the manner in which the research was conducted. The self-report branch of qualitative research is one which is looked upon dubiously as sizeable and longstanding question marks persist to hang over just how reliable it can be deemed to be. In this research, the collated data is entirely reliant upon self-report responses which compromises its validity significantly as it may be skewed by the social desirability effect, where subject wish to provide the response that is seen to be socially acceptable, and the researcher bias effect, where the manner in which the researcher poses their questions leads the participants towards providing the responses they desire. Thus the evidence may not be entirely factual but rather is a more based on what the participants deem as constituting aggressive behaviour.

The sample chosen to partake in the study is not one which could be deemed to be generalizable to teenagers at large as they were drawn from ethnic minority groups from poorer backgrounds where violence was already prevalent. This leads to the possibility that the researchers chose their sample with the aim of producing these sensational results rather than to get generalizable results which could be applied to the broader population.

What features of pseudoscience are on show? The first feature on show is the reliance on anecdotal evidence and self-report measures which is found in the study. Rather than having a set scientific measure of monitoring people’s fizzy drink consumption and levels of aggressive behaviour, the researchers instead choose to rely upon the self-report system of data collection which is characteristic of many pseudoscientific practices. This can be influenced by a whole host of interferences that compromise just how trustworthy this data can be deemed to be and it is this unreliability and absence of accurate scientific basis in the area of data collection that points to the presence of pseudoscience.

There is also an issue with a vagueness of measurement present in this study. The concept of what an act of aggression entails is one which is dogged by ambiguity as at no point is it made known whether the participants merely classed physical violence as aggressive behaviour in their self-report or whether emotional or verbal aggression were also factored into the study. This is a vital area as it may be that a correlation exists only between soft drink consumption and physical aggression and not with verbal or emotional forms of aggressive behaviour. The level of uncertainty created in this regard points to the potential presence of pseudoscience.

Finally, it is possible to identify a lack of parsimony, whereby the explanation with the least assumptions was not employed to explain increased aggression levels. The study fails to allow for the influence of potential external confounding variables such as the social background which are more likely to be a cause for the increased levels of aggression shown in the behaviour of the youths such as age and the level of the poverty their family faces. Such factors are decidedly more probable influences over the participant’s likelihood of carrying a weapon and the degree to which they display aggressive behavioural tendencies.

The moral of the story: Though an associative relationship was established between the variables of aggression and soft drink consumption, it is vital to bear in mind the old adage that “correlation does not imply causation”. The researchers in this instance were far too rash in their willingness to infer causation with a data set that should have been treated in a far more cautious and reserved manner.