Pavlovian Learning & What predicts what

• Pavlovian Learning


  Learning to anticipate/predict something based on a preceding occurrence or situation
• Conditional Stimulus (CS)


  The preceding thing that predicts/signals an upcoming Unconditional Stimulus (US)
• Unconditional Stimulus (US)


  The anticipated/predicted thing
• In Pavlovian conditioning, the experimenter arranges things such that the CS predicts/signals an upcoming US
• In the natural environment, usually one thing predicts/signals another because one is the cause and the other is the effect
• The Pavlovian learning process discovers relationships between predictors (CS or cause) and predicted (US or effect)
• In a lab, the fact that the relationship needs discovering is obscured by the apparent simplicity of the situation: there are only two 'events' – presentation of the CS and of the US
• Eye blink conditioning experiment with rabbits


  • Rabbit in unchanging experimental conditions with only air puff US and tone CS
  • Acquisition of conditioned response (CR) is a slow process needing over 200 trials for rabbits to be reliably blinking (>50%) in response to the CS
• Discovering causes


  • It can be very difficult as there are many possibilities to search through
  • Reducing the number of possibilities to consider can speed up the discovery process
• Possible exclusions when discovering causes


  • Things that are constant
  • Events that occur after the effect
  • Events that sometimes occur before and sometimes after the effect
  • Events that occur too long before the effect and possibly too soon before it or at the same time
  • Events that we already know are not likely to be causes
• Rules of Pavlovian learning


  • Only stimuli that occur before significant events/stimuli are relevant
  • Stimuli that occur both before and after are not relevant
  • Only stimuli that occur within the right period of time are relevant (not too soon and not to long before)
  • Familiar stimuli are not relevant
  • Look out for things that are already known to be causes of related/similar effects
• CS-US belongingness


  If the CS does not 'belong with' the US, the organism will learn to respond much more slowly or not at all
• Threat conditioning in primates


  • Aversive US (often electric shock) and a non-aversive CS (auditory or visually presented)
  • Primates acquire threat CRs (e.g. freezing, running away, increased heart and respiratory rates) when the CS is a picture of snakes or spiders but not when it is of flowers or mushrooms
• Taste/smell aversions


  A special kind of Pavlovian conditioning where a strongly flavoured/smelling food/drink is followed by illness, leading to a strong aversion to that taste/smell
• Characteristics of taste/smell aversions


  • A strong, unusually and/or distinctively flavoured/smelling food/drink is eaten/drunk and then some time later the person falls ill
  • The illness has gastrointestinal symptoms (nausea, vomiting)
  • When the food/drink is encountered again, its smell/taste evoke a very strong aversion
  • Just one such experience is often sufficient
• Taste/smell aversions


  The taste/smell is the CS, the illness symptoms are the UR, and the aversion is the CR
• Taste/smell aversions can be acquired even with a very long CS-US delay (up to 24 hours) and just one experience may be sufficient
• The learning process is easily 'fooled' - if you fall sick after having eaten a novel/strongly/unusually flavoured food/drink you are likely to develop an aversion to it, regardless of the cause of your illness
• CS-US belongingness in taste/smell aversions


  • Many animals will acquire an aversion (CR) to smell and flavour CSs following a very few (often just one) pairings with a sickness inducing US, but not to auditory, visual or tactile CSs
  • Animals are 'prepared' to acquire taste/smell aversions, but not other kinds of food/drink aversions
• Experiment demonstrating CS-US belongingness in taste/smell aversions


  • Two groups of thirsty rats: Group 1 received radiation sickness US, Group 2 received foot shock US
  • Both groups exposed to simultaneous flavour CS and audio-visual CS
  • Group 1 acquired aversion to flavour CS, Group 2 acquired aversion to audio-visual CS
• The flavour CS 'belongs with' the illness inducing US, while the audio-visual CS 'belongs with' the foot shock US