Opinion polls may inadvertently affect public opinion itself as people change attitudes after learning what others think. A disconcerting possibility is that opinion polls have the ability to create information cascades or spirals of silence where the majority opinion becomes increasingly larger over time. Testing this hypothesis on attitudes towards Syrian refugees and mandatory measles vaccination, survey experiments are performed on a population based web panel using a novel automated procedure that measure the influence of an initial poll over subsequent polls. No indications of spiraling opinion gaps over time between the treatment and control groups are identified. The polls do however trigger a cognitive response as the treated respondents become more opinionated and alter their justification for their answers.