Causality and the categorisation of objects and events

The “Tower of London” puzzle was adapted to tablet PCs to be used as a clinical bedside test. “Iso-problems”, a specific class of problems, require identical moves but ball colours are permuted. Thus difficulty is the same even if the appearance is different. We wanted to determine the impact of these as yet little-studied tasks and hypothesised that there may be a learning effect specific to them (the “iso-effect”). We interspersed a set of six iso-problems within one selection of 22 tasks and analysed problem solving by 81 healthy adults (mean age 41.6 years). Participants showed learning across iso-problems (less time, fewer moves, increasingly efficient solutions). This effect was distinct from general learning, as was obvious from comparison with a series of non-isomorphic tasks. However, participants seem not to be aware of solving such problems. This “iso-effect” may be related to implicit memory, a domain that so far has not been assessed using the Tower of London.     

Suicide Clusters: A Review of Risk Factors and Mechanisms

Suicide clusters, although uncommon, cause great concern in the communities in which they occur. We searched the world literature on suicide clusters and describe the risk factors and proposed psychological mechanisms underlying the spatio‐temporal clustering of suicides (point clusters). Potential risk factors include male gender, being an adolescent or young adult, drug or alcohol abuse, and past history of self‐harm. However, the majority of studies lack methodological rigor. Many different psychological mechanisms are described, including contagion, imitation, suggestion, learning, and assortative relating, but supporting empirical evidence is generally lacking. More scientifically rigorous studies are needed to improve understanding of suicide clusters.