Induced Forgetting Is the Result of True Forgetting, Not Shifts in Decision-making Thresholds

Induced forgetting occurs when accessing an item in memory appears to harm memory representations of categorically related items. However, it is possible that the actual memory representations are unharmed. Instead, people may just change how they make decisions. Specifically, signal detection theory suggests this apparent forgetting may be due to participants shifting their decision criterion. Here, we used behavioral and electrophysiological measures to determine whether induced forgetting is truly due to changes in how items are represented or simply due to a shifting criterion. Participants' behavior and brain activity showed that induced forgetting was due to changes in the strength of the underlying representations, weighing against a criterion shift explanation of induced forgetting.

“Only your first yes will count”: The impact of pre-lineup instructions on sequential lineup decisions

When administering sequential lineups, researchers often inform their participants that only their first yes response will count. This instruction differs from the original sequential lineup protocol and from how sequential lineups are conducted in practice. Participants (N = 896) viewed a videotaped mock crime and viewed a simultaneous lineup, a sequential lineup with a first-yes-counts instruction, or a sequential control lineup (with no first-yes-counts instruction); the lineup was either target-present or target-absent. Participants in the first-yes-counts condition were less likely to identify the suspect and more likely to reject the lineup than participants in the simultaneous and sequential control conditions, suggesting a conservative criterion shift. The diagnostic value of suspect identifications, as measured by partial Area Under the Curve, was lower in the first-yes-counts lineup than in the simultaneous lineup. Results were qualitatively similar for other metrics of diagnosticity, though the differences were not statistically significant. Differences between the simultaneous and sequential control lineups were negligible on all outcomes. The first-yes-counts instruction undermines sequential lineup performance and produces an artefactual simultaneous lineup advantage. Researchers should adhere to sequential lineup protocols that maximize diagnosticity and that would feasibly be implemented in practice, allowing them to draw more generalizable conclusions from their data.

Sensorimotor temporal recalibration within and across limbs

Repeated presentation of artificially induced delays between actions and events leads to shifts in participants’ subjective simultaneity towards the adapted lag. This sensorimotor temporal recalibration generalises across sensory modalities, presumably via a shift in the motor component. Here we examined two overlapping questions regarding (1) the level of representation of temporal recalibration (by testing whether it also generalises across limbs) and (2) the neural underpinning of the shift in the motor component (by comparing adaption magnitude in the foot relative to the hand). An adaption-test paradigm was used, with hand or foot adaptation, and same-limb and cross-limb test phases that used a synchrony judgement task. By demonstrating that temporal recalibration occurs in the foot, we confirmed that it is a robust motor phenomenon. Shifts in the distribution of participants’ synchrony responses were quantified using a detection-theoretic model of the SJ task, where a shift of both boundaries together gives a stronger indication that the effect is not simply a result of decision bias. The results showed a significant shift in both boundaries in the same-limb conditions, whereas there was only a shift of the higher boundary in the cross-limb conditions. These two patterns most likely reflect a genuine shift in neural timing, and a criterion shift, respectively.