This is incorrect and unhelpful. Science in fields with lots of complexity, such as neuroscience and psychology, suffer from hard problems such as unmeasured ca

This is incorrect and unhelpful. Science in fields with lots of complexity, such as neuroscience and psychology, suffer from hard problems such as unmeasured causal variables and divergent sample characteristics. You might chalk this up to incompetence, but there are are in fact real concerns of feasibility. You cannot hope to measure or control all relevant cognitive factors, you just try to balance your sample groups on the more obvious measures, increase your sample size, then hope that other differences average out with random assignment.