Speaker: Emeritus Professor Robert (Bob) Boakes (University of Sydney)

Title: The monkey, the lettuce leaf, sugar and disappointment: From translation to discovery

Abstract: For some years our group has run translational experiments to study metabolic and cognitive impairments in rats that have drunk large amounts of a sugar solution.  Metabolic problems have included development of large amounts of visceral fat, while the cognitive changes include poor performance on spatial learning and memory tasks.  We have also studied recovery from the impact of sugary drinks when the rats no longer had access to such solutions.  To model a human change from, say, classic Coca Cola to Diet Coke, we have switched rats from a sugar to a saccharin solution.  Although the saccharin solutions were ones that are normally liked by rats, in these sugar->saccharin ‘switch’ experiments intakes remained unexpectedly low.  Consequent experiments confirmed that we had stumbled upon an unusually persistent successive negative contrast effect.  It seems that, when expecting a delicious drink and instead experiencing something that isn’t quite as nice, disappointment supports conditioning of a lasting aversion to the new drink.