Parametric effects of word frequency in memory for mixed frequency lists

The word frequency paradox refers to the finding that low frequency words are better recognized than high frequency words yet high frequency words are better recalled than low frequency words. Rather than comparing separate groups of low and high frequency words, we sought to quantify the functional relation between word frequency and memory performance across the broad range of frequencies typically used in episodic memory experiments. Here we report that both low frequency and high frequency words are better recalled than midfrequency words. In contrast, we only observe a low frequency advantage when participants were given a subsequent item recognition test. The U-shaped relation between word frequency and recall probability may help to explain inconsistent results in studies using mixed lists with separate groups of high and low frequency words.