False memory implantation studies are characterised by suggestions indicating that specific unremembered events occurred, attributing suggested events to a knowledgeable source (e.g., parents), and including true events that provide evidence that this source was consulted. These characteristics create a particular retrieval context that influences how individuals come to believe that false events occurred. Two studies used a variant of implantation methods to vary the proportion of events attributed to parents and the presence of true events within the suggestion. In Study 1 participants received six false events, and were told that all or some events came from parents. Participants told that all of the events came from parents formed more and stronger false beliefs. In Study 2 participants also received two true events, and a third group was told that half of the events came from their parents. Participants given the specific ratio ("half") endorsed more false beliefs, and beliefs between the other groups no longer differed. Across both studies participants told that some events came from parents reported stronger memory phenomenology. The effect of suggestions on false beliefs in implantation studies depends partly on the credibility of suggestions derived from providing information about the source of suggested events.