Barrera 1977

Methods	Randomised controlled trial with three groups.
Participants	Country: USA. Setting: NA. Health problem: snake phobia. Recruitment: adverts. Participants: adults (n=24).
Interventions	Contract features: Form: written; Parties: NA; Incentives: other; Co‐interventions: yes. Group 1: Self administered desensitisation workbook. Group 2: Self administered desensitisation workbook with contract to reward self for completion of workbook. Group 3: Placebo.
Outcomes	Number of desensitisation sessions attended; time spent studying materials.
Notes
Risk of bias
Item	Authors' judgement	Description
Allocation concealment?	Unclear	B ‐ Unclear