No abstract

Research has shown that consistently right-handed individuals have poorer memory than do inconsistently right- or left-handed individuals under baseline conditions but more reliably exhibit enhanced memory retrieval after making a series of saccadic eye movements. From this it could be that consistent versus inconsistent handedness, regardless of left/right direction, is an important individual difference factor in memory. Or, more specifically, it could be the presence or absence of consistent right-handedness that matters for memory. To resolve this ambiguity, we compared consistent and inconsistent left- and right-handers on associative recognition tests taken after saccades or a no-saccades control activity. Consistent-handers exhibited poorer memory than did inconsistent-handers following the control activity, and saccades enhanced retrieval for consistent-handers only. Saccades impaired retrieval for inconsistent-handers. None of these effects depended on left/right direction. Hence, this study establishes handedness consistency, regardless of direction, as an important individual difference factor in memory.

No abstract

Making repetitive saccadic eye movements has been found to increase subsequent episodic memory retrieval and also to increase subsequent top-down attentional control. We theorise that these effects are related such that saccade-induced changes in attentional processing facilitate memory retrieval. We tested this idea by examining the effect of saccade execution on retrieval conditions that differed in relative ease of consciously accessing episodic memories. Based on recent theories of episodic retrieval, we reasoned that there is a larger role for top-down attention when memories are more difficult to access. Consequently, we expected saccade execution to have a greater facilitative effect on retrieval when memories were more difficult to access. We obtained the expected result in a recall procedure in Experiment 1 and in a recognition procedure in Experiment 2. We also examined an individual difference factor--consistency of handedness--as a possible moderator of saccade execution effects on retrieval. We discuss how our top-down attentional control hypothesis can be extended to explain beneficial effects of saccade execution on other types of cognition, as well as negative effects on retrieval in some cases.

Individuals who do not consistently use the same hand to perform unimanual tasks (inconsistent-handed) outperform consistent right- and left-handed individuals on tests of episodic memory. We explored whether the inconsistent-hander (ICH) memory advantage extends to memory for unimanual hand use itself. Are ICHs better able to remember which hand they used to perform actions? Opposing predictions are possible, stemming from the finding that some regions of the corpus callosum are larger in ICHs, especially those that connect motor areas. One hypothesis is that greater callosally mediated interhemispheric interaction produces ICHs’ superior retrieval of episodic memories, and this may extend to episodic memories for hand use. Alternatively, we also hypothesized that greater interhemispheric interaction could produce more bilateral activation in motor areas during the performance and retrieval of unimanual actions. This could interfere with ICHs’ ability to remember which hand they used. To test these competing predictions in the current study, consistent- and inconsistent-handers performed unimanual actions, half of which required manipulating objects and half of which did not. Each action was performed four times in one of five conditions that differed in the ratio of left to right hand use: always left (4:0), usually left (3:1), equal (2:2), usually right (1:3), or always right (0:4). We compared consistent- and inconsistent-handers on recall of the left:right ratio for each action. ICHs remembered how they performed actions better than consistent-handers, regardless of ratio. These findings provide another example of superior episodic retrieval in ICHs. We discuss how greater interaction might benefit memory for hand use.