How memory changes with time: From bees to humans

Abstract

Memory is crucial for guiding animals as to where, when and on what to forage, whom to mate with and how to detect and evade predators. The contents of memory can change over time; either passively, where details are forgotten, or by reactivating and consolidating memories, in which previously stored and new information effect the final memory. In humans the fallibility of memory is well studied, with many errors known to effect declarative memory. However, little is known about the potential occurrence of such memory errors in non-human animals. In this thesis I investigate how memory changes over time using key model organisms of memory; the bumblebee and the honeybee. Additionally, I explore errors in human memory. In Chapter two I explore memory degradation for colour patterns over time in bumblebees. I find no difference in memory decay if patterns are symmetrical around a vertical axis (an arrangement innately preferred) or not. However, not all information is forgotten over time: information about the colour contained in the pattern is retained, whilst the details of the overall configuration of the target flower are lost. In Chapter three I show for the first time in a non-human animal ‘merging’ of long-term memories. Bumblebees trained to two artificial flower types show a preference for a previously unseen hybrid of the two. This is similar to the memory conjunction error shown by humans. In Chapter four I find no biasing effect of postevent cues, akin to the misinformation effect in humans, in either bumblebees or honeybees. However I note the methodological difficulties in examining this type of memory error in an insect model. Finally, in Chapter five I look at a known error in human memory and show how semantic false memories may be an inevitable by-product of the adaptive cognitive process of categorisation.