Lecture 5- Learning and the control of dietary behavior Flashcards
Why do we need to learn?
obtain sufficient food energy to meet requirements for maintenance, growth, and activity
obtain sufficient quantities of essential macro- and micro-nutrients
avoid ingesting harmful substances
What are the 2 key things that humans need to do with food with regards to learning?
be able to exploit food resources when they become available
to know (learn) which foods are safe to eat and are good sources of nutrients and energy
What is The omnivore’s paradox?
As omnivores, the most unselective eaters, humans are faced with a wide variety of food choices, resulting in a dilemma.
Arguably, modern food preservation and transportation technologies, this particular dilemma was resolved primarily through cultural influences.
These technologies have recreated the dilemma, by making available foods that were previously seasonal or regional.
Gibson & Wardle (2003)
young children can discriminate against food according to their energy density; which is expressed through their preferences; they are orientated towards higher density foods
Is taste a good predictor of energy density?
Sweetness is NOT a good predictor of energy content
Can’t rely on basic taste characteristics
INSTEAD learning plays an important role-we have to experience foods
What is flavour preference learning?
Food (US) normally elicits salivation (the UR [unconditioned response])
But when CS (novel stimulus) and US are paired, the CS becomes able
to elicit a CR [conditioned response]
Garcia- associative learning
can form an association between the sensory characteristics of a food and its post-ingestive affects
What is special about conditioned taste aversions?
Showed that conditioned taste aversions could be seen over a 24hour lapse; unlike the traditional view about classical conditioning:
Conditioned taste aversions challenges:
The need for close temporal contiguity
AND the need several exposures for learning to take place
As you only need 1 exposure
Can you be conditioned to avoid food?
Garcia demonstrated a clear predisposition to associate flavors with illness
Bait shyness (nausea and bait)
BUT Garcia found it is DIFFICULUT to from an association between sweet taste and pain
I.E. NOT every CS can form an association between US
What are the 3 challenges of CTA?
Temporal contiguity (rapid learning within 24 hours)
Can occur after 1 exposure
Clear predisposition to associate flavours with illness (rather than associated stimuli)
Sclafani (1997)
Flavor-nutrient learning
energy can reinforce changes in flavour preferences
Animals will learn an association between a novel flavor and how it might signal the infusion of nutrients drawn into the stomach VERY quickly
F-N learning is abundant in animals…
Demonstrations of F-N preference conditioning are quite rare in humans
Why is F-N learning rare in humans?
Evidence learning greater in children; perhaps between they have encountered fewer flavor?
Greater array of flavors inhibits learning ability to discriminate
Lack of F-N learning…is it down to the issues in the western diet?
Lack of flavor nutrient experiments due to too many flavors
Western diets inhibited our ability to test different types of flavors
NO:
Look at Samburu – semi-nomadic pastoralists who have a less varied diet
FOUND:
NO evidence for flavor-nutrient learning thus perhaps variety of flavors does not account for the fact that we stop learning about flavors
How has our diet different to hunter-gatherer populations?
Because historically humans not used to energy dense food; today we are constantly exposed to HIGH energy dense food which…
Has HUGE effects on ability to discriminate against very energy dense food
Lack of F-N learning and physiology
Humans are poorly adapted to energy rich foods
We do not have the capacity to discriminate between energy density
Testing foods are far more energy dense that what we are naturally designed to be able to discriminate against
Thus, don’t have the physiology for it
NOT well adapted to discriminating energy rich foods
And in flavor-nutrient learning studies we are arguably exposing pps to very high energy dense foods
Alternative: How else could we learn about Preferences?
Flavour-flavour learning – taking a ‘short cut’
Affective quality of the already liked flavor will rub off on the conditioned stimulus
Transfers affect from Unconditioned to the conditioned stimulus
If something is already liked and it is presented with something novel
You will learn to like it!
Zellner
The flavors are presented in the absence of sucrose (taken away unconditioned stimulus) to show the transfer of affects
The flavor that was previously paired with the sweet tasting solution, is now more liked than cs-
Demonstrating a transfer of “liking”
Evidence of flavor flavor learning
Zajonc (1968)
“Attitudinal Effects of Mere Exposure”
Simple, unreinforced exposure leads to increased liking for a stimulus.
Chili
Stevenson & Yeomans (1995)
FOUND:
EVEN though low dose becomes increasing intense with regards to burn intensity
IT ALSO becomes increasingly LIKED
Argue:
There is a dissociation between the change in taste characteristics and intensity of burn sensation and liking
Attributed to an increased acceptance (NOT decreased intensity as actually more intense chilli was liked more) due to mere exposure effect
ONLY tells us about the mere acceptance of the consumption of a novel food NOT about the craving or desire of foods
Awareness and dietary learning
FLAVOUR learning show that forms of CC conditioning occur outside conscious awareness
CS-US contingency awareness might NOT be necessary in:
▪ Flavour-flavour learning
▪ Caffeine conditioning
▪ CTA’s
Dietary learning may be…
Unusual
Automatic
‘Primitive’
Dependent solely on CS-US presentation
Able to accommodate long CS-US contingencies