Expectations vs Reality
What the meme means for your mental health
I downloaded a scammy-looking shopping app on my phone the other day. As soon as I opened the app, a “spin a wheel” for discounts popped up on the screen. From my prior knowledge about lotteries and expectations about companies wanting to maximize their profits, I expected no jackpot — perhaps a 10% discount at best.
But, lo and behold- the jackpot hit home on the first try!
EXPECTATION: Insignificant discount reward
REALITY: Jackpot!!!
Now having used the app for 6 months and getting a jackpot every time I spin, the next time I open the app I expect the jackpot.
EXPECTATION: Jackpot
REALITY: Jackpot
It’ll be a horrible shock when I don’t hit the jackpot the next time I want to make a big purchase on the app.
EXPECTATION: Jackpot
REALITY: No Jackpot!!!
There is of course a discrepancy between the expectation and the reality in two out of the three scenarios painted above.
Notice also, however, how the expectation changed after the first discrepancy — how we went from expecting no significant reward to expecting a jackpot.
Based on your past experiences and current reality the brain makes predictions about rewards you might receive.
A prediction error is the failure of the brain’s accuracy in the prediction about the reward.
It is the difference between the predicted and received reward.
Dopamine neurons in the midbrain of humans, monkeys, and rodents typically respond to deviations from expected rewards.
- When rewards exceed expectations, these neurons become more active (positive prediction error).
- When rewards match expectations, their activity remains unchanged (no prediction error).
- Conversely, when rewards are less than expected, their activity decreases (negative prediction error).
The reward prediction errors help update predictions when there is a discrepancy between the prediction and the received reward. This process underlies human learning. It helps update expectations and be better prepared for the future.
You might have heard this grandma’s saying” Keep your expectations low and you will never be disappointed”.
Now you know the neuroscience behind this…
If your predictions and expectations of reward are low, getting a larger reward will trigger the dopamine neurons and create a positive prediction error.
The brain can make mistakes sometimes regarding these prediction error mechanisms.
For example, if you’ve been exposed to a certain stimulus many times with no reward following it, the brain should ideally not link the stimulus to a reward. Or, if there’s already a stimulus-reward link established in your brain, and you’re exposed to a new stimulus on top of the first that also links to the same reward, the healthy brain wouldn’t take the trouble to learn the new stimulus since it’s not adding anything new. These are processes the healthy brain does prevent learning irrelevant things.
People with mental illnesses like schizophrenia and depression have abnormal reward prediction error mechanisms.
The Prediction Error Hypothesis of Schizophrenia states that individuals with schizophrenia exhibit heightened attention to irrelevant details, which is associated with positive symptoms of the disorder. Conversely, they demonstrate a reduced ability to learn from cues indicating potential rewards, a characteristic linked to negative and cognitive symptoms. But this is just a hypothesis
- Takeaway: Reward learning tasks and prediction error abnormalities can be used to detect and predict mental illnesses like schizophrenia and depression.
Written in collaboration with
.References:
Schultz W. Dopamine reward prediction error coding. Dialogues Clin Neurosci. 2016;18(1):23–32. doi:10.31887/DCNS.2016.18.1/wschultz
Millard, S.J., Bearden, C.E., Karlsgodt, K.H. et al. The prediction-error hypothesis of schizophrenia: new data point to circuit-specific changes in dopamine activity.Neuropsychopharmacol. 47, 628–640 (2022). https://doi.org/10.1038/s41386-021-01188-y
