A key phenomenon in inductive reasoning is the diversity effect, whereby a novel property is more likely to be generalized when it is shared by an evidence sample composed of diverse instances than a sample composed of similar instances. We outline a Bayesian model and an experimental study that show that the diversity effect depends on the assumption that samples of evidence were selected by a helpful agent (strong sampling). Inductive arguments with premises containing either diverse or nondiverse evidence samples were presented under different sampling conditions, where instructions and filler items indicated that the samples were selected intentionally (strong sampling) or randomly (weak sampling). A robust diversity effect was found under strong sampling, but was attenuated under weak sampling. As predicted by our Bayesian model, the largest effect of sampling was on arguments with nondiverse evidence, where strong sampling led to more restricted generalization than weak sampling. These results show that the characteristics of evidence that are deemed relevant to an inductive reasoning problem depend on beliefs about how the evidence was generated.
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Victims of repeated incidents of abuse are often required to report incident-specific information about particular instances of the abuse. In the current study, we explored adults’ capability of such a task by examining the difference in memory for single versus repeated events that were either stressful or nonstressful. One hundred and twenty-two female participants engaged in either a single event or four highly similar events over a 4-week period. During each event, participants read and imagined themselves partaking in a hypothetical relationship scenario that consisted of either a domestic violence encounter (stressful group) or a closely matched neutral relationship encounter (nonstressful group). One week after the final scenario, participants completed recall and recognition questions about the target scenario. The findings revealed that although emotional stress had an enhancing effect on long-term memory, it did not interact with event frequency (single, repeated) for most memory measures. However, regardless of emotional stress, repeated-event participants struggled to report particular details about the target scenario, and showed greater source monitoring issues than single-event participants. Conversely, when a broader definition of memory accuracy was used that encompassed all experienced details, repeated and single event groups performed similarly. Together, the findings indicate that the testimonies of adult female complainants of repeated abuse will mostly likely consist of details that occurred across multiple experienced events, and that this will be similar regardless of whether emotional stress was or was not experienced during the event(s). The findings are discussed in terms of theoretical and practical implications.
A key phenomenon in inductive reasoning is the diversity effect, whereby a novel property is more likely to be generalized when it is shared by an evidence sample composed of diverse instances than a sample composed of similar instances. We outline a Bayesian model and an experimental study that show that the diversity effect depends on the assumption that samples of evidence were selected by a helpful agent (strong sampling). Inductive arguments with premises containing either diverse or nondiverse evidence samples were presented under different sampling conditions, where instructions and filler items indicated that the samples were selected intentionally (strong sampling) or randomly (weak sampling). A robust diversity effect was found under strong sampling, but was attenuated under weak sampling. As predicted by our Bayesian model, the largest effect of sampling was on arguments with nondiverse evidence, where strong sampling led to more restricted generalization than weak sampling. These results show that the characteristics of evidence that are deemed relevant to an inductive reasoning problem depend on beliefs about how the evidence was generated.
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