The influence of intervening tasks on memory

Learning new information is rarely done in isolation outside the laboratory. What one does between study sessions is important for later retrieval of the studied material. Previous research has shown that interleaved semantic retrieval leads to enhanced memory for later-learned items but to reduced memory for earlier-learned items (Divis & Benjamin, 2014). Retrieval-induced distinction provides one account for the opposite effects of retrieval on memory for early versus later material. By that view, retrieval serves to "spread out" the memory representations, making them (1) more distinct and less likely to interfere with each other and (2) rendering earlier events mentally more distant and harder to access at the time of test. Here, I expand on prior work examining the influence of intervening tasks on memory. Experiment 1 examines the effect of interleaved periods of task switching on memory for materials learned prior to or following the task switching intervention. Switching tasks (50% retrieval and 50% control) between periods of learning leads to similar benefits as those provided by a retrieval intervention. Experiments 2A and 2B examine the effects of intervening task on interlist intrusions. List distinction is enhanced when lists are separated by retrieval tasks, as seen by a reduction in interlist intrusions. Experiment 3 integrates and extends many of the components of prior studies by examining the influence of intervening retrieval on memory for complex, narrative text materials that share repeated, conflicting, and unique information. It highlights important boundaries to the influence of retrieval-induced distinction and provides a launching point for future studies examining the application of these intervening tasks in more ecologically relevant settings

Does fundamental-frequency discrimination measure virtual pitch discrimination?

Studies of pitch perception often involve measuring difference limens for complex tones (DLCs) that differ in fundamental frequency (F0). These measures are thought to reflect F0 discrimination and to provide an indirect measure of subjective pitch strength. However, in many situations discrimination may be based on cues other than the pitch or the F0, such as differences in the frequencies of individual components or timbre (brightness). Here, DLCs were measured for harmonic and inharmonic tones under various conditions, including a randomized or fixed lowest harmonic number, with and without feedback. The inharmonic tones were produced by shifting the frequencies of all harmonics upwards by 6.25%, 12.5%, or 25% of F0. It was hypothesized that, if DLCs reflect residue-pitch discrimination, these frequency-shifted tones, which produced a weaker and more ambiguous pitch than would yield larger DLCs than the harmonic tones. However, if DLCs reflect comparisons of component pitches, or timbre, they should not be systematically influenced by frequency shifting. The results showed larger DLCs and more scattered pitch matches for inharmonic than for harmonic complexes, confirming that the inharmonic tones produced a less consistent pitch than the harmonic tones, and consistent with the idea that DLCs reflect F0 pitch discrimination