Sequential Presentation Protects Working Memory From Catastrophic Interference

Neural network models of memory are notorious for catastrophic interference: Old items are forgotten as new items are memorized (French, 1999; McCloskey & Cohen, 1989). While working memory (WM) in human adults shows severe capacity limitations, these capacity limitations do not reflect neural network style catastrophic interference. However, our ability to quickly apprehend the numerosity of small sets of objects (i.e., subitizing) does show catastrophic capacity limitations, and this subitizing capacity and WM might reflect a common capacity. Accordingly, computational investigations (Knops, Piazza, Sengupta, Eger & Melcher, 2014; Sengupta, Surampudi & Melcher, 2014) suggest that mutual inhibition among neurons can explain both kinds of capacity limitations as well as why our ability to estimate the numerosity of larger sets is limited according to a Weber ratio signature. Based on simulations with a saliency map-like network and mathematical proofs, we provide three results. First, mutual inhibition among neurons leads to catastrophic interference when items are presented simultaneously. The network can remember a limited number of items, but when more items are presented, the network forgets all of them. Second, if memory items are presented sequentially rather than simultaneously, the network remembers the most recent items rather than forgetting all of them. Hence, the tendency in WM tasks to sequentially attend even to simultaneously presented items might not only reflect attentional limitations, but also an adaptive strategy to avoid catastrophic interference. Third, the mean activation level in the network can be used to estimate the number of items in small sets, but it does not accurately reflect the number of items in larger sets. Rather, we suggest that the Weber ratio signature of large number discrimination emerges naturally from the interaction between the limited precision of a numeric estimation system and a multiplicative gain control mechanism.     

Coping,caring and believing: The embodied work of disaster recovery workers

This paper examines the embodied experiences of coping, caring and believing by disaster recovery workers in Australia in the context of the growing frequency and intensity of disasters, especially bushfires. The study draws on three concepts: faith as performative, embodiment, and the ‘holding environment’ as a system that shapes coping capacity. Faith emerges in the study as having two modalities (introspection and group-communion) that are not synonymous with religious adherence. Instead it is linked to the holding environment, which comprises the strategies that individuals and groups have developed to cope with risks and exposure, through their embodied responses, and the observed responses of others, to the impact of potential and actual harm. The holding environment provides mental, spiritual and physical spaces and practices where disaster recovery workers can safely confide, reflect, debate, grow and heal. These processes, in turn, provide anchor points and sense of purpose. They also accentuate the individual and collective choices we face in terms of mitigating and adapting to growing social and environmental uncertainty with climate change.     

1～6秒时距认知分段性特征

时距认知分段性指不同长度时距的加工机制和表征方式是不同的。以往研究者对1 s以上时距认知的分段性仍存在分歧,为了探讨这一主题,本研究设计了实验1和实验2。实验1采用时间复制任务比较高、低工作记忆容量被试在完成1~6 s视、听时距加工的成绩,结果发现,时距长度与工作记忆容量或通道均存在交互作用,被试在复制1 s、2 s的平均复制时距、复制比率及变异系数没有随工作记忆容量或通道而变化,而复制3 s、4 s、5 s及6 s时,高WMC组较低WMC组或听觉组较视觉组,平均复制时距显著更长、复制比率显著更高、变异系数显著更小。实验2采用时间产生任务比较高、低工作记忆容量被试在完成1~6 s视、听时距加工的成绩,结果也发现,时距长度与工作记忆容量或通道均存在交互作用,被试在产生1 s、2 s的平均产生时距、产生比率及变异系数没有随工作记忆容量或通道而变化,而产生3 s、4 s、5 s及6 s时,高WMC组较低WMC组或听觉组较视觉组,平均产生时距显著更短、产生比率显著更低、变异系数显著更小。这意味着1~6 s的时距认知存在分段性,大约2~3 s可能为分段临界点。时间认知的分段性可以用时间工作记忆说解释,该假说是时间认知分段综合模型解释短时距加工分段性的具体表现形式。