Example SAQ – How agonists affect behaviour

Travis DixonAssessment (IB), Biological Psychology

Read an example SAQ for the tricky topic - agonists.

The “additional terms” that have been added to Paper 1 SAQs in IB Psychology can be a nuisance. However, there are ways to address the potential questions without adding too much content to your course. This post shows you an example SAQ that uses Passamonti et al.’s study on neurotransmission for a potential answer on agonists and behaviour. 

Get more exam tips, example SAQs and study resources for the “additional terms” with this downloadable PDF.

An agonist is a chemical messenger that binds to the receptor sites of neurons and activates them to create a response. Some drugs act as agonists of specific neurotransmitter sites. For example, pramipexole is an agonist of dopamine receptor sites. It binds to dopamine and mimics the effects. This could be an effective treatment for people with depression (as low dopamine levels could be one etiology of depression). Read more here….

However, agonists don’t necessarily have to be introduced into the brain from external sources like drugs. Neurotransmitters themselves, like serotonin, are endogenous agonists. This means they occur naturally in the brain. If you’re asked to explain agonists and their potential effect on behaviour, you can write about drugs like pramipexole or endogenous agonists like serotonin.

Read more:

Neurotransmission is how signals get sent around the brain. The pre-synaptic neuron fires neurotransmitters like dopamine and serotonin across the synapse (the gap between neurons) and they bind to the receptor sites on the post-synaptic neuron. Agonists bind to those receptor sites and mimic the signal of a neurotransmitter.

When writing good short answer responses in IB Psychology, I recommend using the same general structure every time, regardless of the command term. The example below, along with the 17 other examples in this resource, follow that structure.

Agonists and Behaviour (Biological Approach)

Question: Describe the effect of one agonist on human behaviour.  Comments

One agonist is serotonin, which is a naturally occurring agonist of 5HT receptors. The effects of this on behaviour can be shown in Passamonti et al.’s study.

An agonist is a chemical that amplifies the effect of a neurotransmitter by binding to the receptor sites of that neurotransmitter and activating them. This is opposite of an antagonist which binds to receptors and blocks them from firing. Neurotransmitters have an effect by binding to receptor sites and sending messages through neural networks. Agonists influence this process because they increase the activation of receptors. Many drugs are agonists. For example, pramipexole is a drug for Parkinson’s disease and it works by binding to the receptors of the neurotransmitter dopamine.

But neurotransmitters themselves can be endogenous (naturally occurring) agonists. For example, selective serotonin reuptake inhibitory drugs (SSRI’s) naturally increase the levels and activity of endogenous 5HT (serotonin). Therefore, serotonin can be considered an endogenous (naturally occurring) agonist of 5HT (serotonin) receptor sites. Disruptions to serotonin transmission can influence behaviour.

The connection between serotonin and behaviour can be explained using Passamonti’s study. The aim of this study was to see what effect reduced serotonin has on the prefrontal cortex (PFC) when exposed to threat. Participants consumed a placebo drink or one lacking tryptophan (a key amino acid in the building of serotonin in the brain) which reduced serotonin levels. They were placed in an fMRI machine and were shown a variety of different faces (e.g. angry, happy, sad). Participants who drank the serotonin-depleting drink had reduced function in their PFC when they were perceiving images of angry faces while in the fMRI.

The results also showed that reduced serotonin disrupted the neural network communication between the amygdala and the PFC when viewing angry faces. The reduced function in the PFC when exposed to angry faces (a threat) could explain serotonin’s link with aggression – people can’t inhibit their impulsive reaction to the threat because serotonin is affecting the part of the brain that helps us to stop acting impulsively and they might react to threat violently.

In conclusion, if serotonin’s activity as an agonist on 5HT receptors is reduced it can affect the transmission in important parts of the brain like the PFC and amygdala and this can affect behaviour, like aggression (Approx. 360 words).


Restating the question and stating the study helps show the examiner that you’re going to get to the point and answer the question properly. 

Remembering really clear, accurate and concise definitions helps show you know the topic. 

The key to getting a 7 in Paper One is writing three excellent SAQs. See how here.

Most students only write about the study and don’t include a central argument – this means they’re not showing their knowledge and understanding of the topic.

Remember that even though the question doesn’t say anything about a study, every SAQ must have at least one.

The results are the most important aspect of any study. However, you have to make sure your answer doesn’t finish with just stating the results-  you have to make a specific link between the results and the question you’re answering (or the point you’re making).

Good SAQs answer the question – this answer addresses the specific effect of the agonist on human behaviour.


The conclusion is not always necessary in SAQs. However, in this example it helps to explicitly link the example and the study back to the topic – agonists.




We don’t need to get too complicated when it comes to writing excellent IB Psychology SAQs. Simply outline your answer with a basic introduction, explain the topic in a central argument and use supporting evidence (a study) to support your arguments. Round it out with a basic conclusion, if necessary, and voila. Job done.