Tests of correlations between extinctions and reversals are difficult for a number of reasons. Statistical analysis shows no evidence for a correlation between reversals and extinctions. There were no significant periods of sustained growth reversals. List of the beginning and end of geomagnetic reversals. Hypotheses have also advanced toward linking reversals to mass extinctions. There is evidence that this occurs both during secular variation and during reversals. Exposure leads to reductions or reversals of normal gender differences. Reversals and counter moves were also made much more commonplace. Variations include extending the ABA design with repeated reversals (ABAB) and including multiple treatments (ABCABC). The club went through startling reversals of fortune in the next two seasons. Finally, Cardwell discovered the existence of positive and negative reversals in the RSI. He amassed a record of 4,152 convictions and 25 reversals. The seasonal wind reversals would affect trade circulations. The rate of reversals in the Earth's magnetic field has varied widely over time. The magnetic banding directly corresponds with the Earth's polar reversals.