Two Key Studies of Agonists & Antagonists: Crockett et al. (2010) & Romach et al. (1999) (HL IB Psychology)

Key Study 1 (Agonist): Crockett et al. (2010)

Aim: To investigate the role of a serotonin agonist (SSRIs specifically) in prosocial behaviour (e.g. deciding that harmful behaviours towards others are unacceptable).

Participants: 24 males from Cambridge in the UK with a mean age of 25.6 years. The participants were screened for psychiatric and neurological disorders before the study began.

Procedure: The participants were given either an SSRI (Citalopram), a drug used to treat ADHD or a placebo. The experiment used a double-blind design.

The first part of the procedure involved participants being asked to make moral judgements about a series of hypothetical scenarios, for example:

1. Would you push someone in front of a train if it meant saving five other people? This was the emotionally salient ‘personal harm’ condition i.e. the idea involves actually physically pushing someone in front of a train

2. Would you flick a switch so that a train hits one person instead of five? This was the less emotionally salient ‘impersonal harms’ condition i.e. the idea involves harming someone at a distance and is thus less personal

The responses were measured according to how many times each participant judged that an action (personal or impersonal harm) was ‘acceptable’.

Results: The emotionally salient personal harm condition (i.e. the idea of actually pushing someone in front of a train) produced the lowest number of ‘acceptable’ responses in both conditions i.e. participants were reluctant to imagine themselves physically harming another person even to save five other lives.  

Participants in the SSRI condition (who had been taking Citalopram) made more prosocial responses i.e. by condemning harmful actions, compared to the ADHD drug group and the placebo group. The moral judgements made by the ADHD drug group and the placebo group were similar, showing no significant differences in prosocial responses.

Conclusion: Some SSRIs, such as Citalopram, may function as serotonin agonists, enhancing the effect of the serotonin in the brain which in turn may promote prosocial behaviour.

Evaluation of Crockett et al. (2010)

   Strengths

• The use of a double-blind procedure increases the internal validity of the findings

  • Screening the participants for psychiatric and neurological disorders before the study also increases the validity of the findings as it helps to factor out any possible confounding variables linked to mental illness 

   Limitations

• A sample of 24 participants is very small and reduces both the reliability (due to a lack of statistical power) and generalisability (again, due to the sample size) of the findings

  • The study used an independent measures design so the differences in prosocial behaviour could simply be due to participant variables e.g. participants in the SSRI group may simply all have been naturally more prosocial than those in the other two groups

Key terms:

• SSRIs  

• Serotonin  

• Double-blind  

Key Study 2 (Antagonist): Romach et al. (1999)

Aim: To investigate the role of a dopamine antagonist (ecopipam), in the treatment of cocaine addiction.

Participants: A self-selecting sample of 15 participants (3 women, 12 men, aged 26-44 years with a mean age = 34 years) who were cocaine addicts.

Procedure:  The study took place over two weeks during which the participants were hospitalised to ensure that experimental controls could be guaranteed. The procedure used a randomised double-blind design with 4 conditions: participants took either a placebo,10mg, 25mg, or 100mg of ecopipam orally on 4 separate occasions.

Two hours after the placebo or ecopipam had been taken each participant was injected with 30mg of cocaine. The participants were assessed for the subjective (individual) effects of having taken cocaine e.g. biological measures such as blood pressure and heart rate and psychological measures, e.g. feelings of being ‘high’ or feelings of anxiety, confusion, feeling the effect of the drug etc. All of the participants were asked about their desire to take cocaine which was an important measure as this would indicate how effective ecopipam was in reducing cravings for cocaine.

Results: Participants in the dopamine antagonist group (who had been taking ecopipam) reported reduced feelings of euphoria and of being ‘high’ (which is the opposite of what would normally follow a cocaine hit). The ecopipam also appeared to reduce the anxiety associated with taking cocaine e.g. withdrawal, and worry about how to ‘score’ the next hit. Participants who took ecopipam expressed less desire to use cocaine than those in the placebo group. The most effective dosage of ecopipam was found to be between 25mg and 100mg.

Conclusion: Some drugs such as ecopipam may function as dopamine antagonists and may be effective in reducing the craving for cocaine as well as the effects of taking cocaine.

Evaluation of Romach et al. (1999)

   Strengths

• This study has useful application as the findings could be used to inform further treatment of cocaine addicts, and possibly those addicted to other substances such as alcohol

  • The use of several different measures e.g. heart-rate, self-reported anxiety means that the study used triangulation which increases the validity of the findings

   Limitations

• Self-reported data is prone to social desirability bias e.g. the participants may have reported reduced feelings of craving to please the researchers or to project a more positive image of themselves and their recovery from drug addiction

  • The study does not tell us what happened after the addicts left the safe, controlled environment of the hospital – it could be that some of the ecopipam group relapsed quickly which would mean that the drug had no real effect long-term

Key terms:

• Ecopipam  

• Dopamine  

• Cravings