What are Effects?
An effect (or bias) describes a systematic psychological or behavioral pattern that humans exhibit in specific situations. These are the defaults evolution gave us — they helped our ancestors survive rapidly in ancient environments, but in our complex modern world they often become blind spots in our judgment.Effects are the bugs in your mental firmware. Recognizing them is the first step to debugging them.This category covers 50 core psychological effects, organized into three groups:
- Cognitive Biases: systematic distortions in how we process information
- Social Psychology Effects: behavioral patterns that emerge in human interaction
- Behavioral Economics Effects: irrational patterns in economic decision-making
Cognitive Biases
Dunning-Kruger Effect
The less competent, the more confident; the more expert, the more humble
Confirmation Bias
We seek evidence that supports what we already believe
Anchoring Effect
The first number we encounter anchors all subsequent judgments
Framing Effect
How information is presented changes how we evaluate it
Recency Bias
Recent events carry disproportionate weight in our judgments
Primacy Effect
First impressions are disproportionately powerful and persistent
Hindsight Bias
After the fact, we feel we “always knew” what would happen
Survivorship Bias
We only see the winners; the failures are invisible
Availability Heuristic
The easier something is to recall, the more likely we think it is
Negativity Bias
Bad news has far greater impact than equally significant good news
Optimism Bias
We systematically underestimate the probability that bad things will happen to us
Self-Serving Bias
We attribute successes to ourselves and failures to external factors
Fundamental Attribution Error
We overweight character and underweight context when judging others
Curse of Knowledge
Once you know something, you can no longer imagine not knowing it
Illusory Correlation
We perceive relationships between things that are actually unrelated
Projection Bias
We assume others share our thoughts, feelings, and preferences
Normalcy Bias
We underestimate disasters because “it’s never happened before”
Social Psychology Effects
Halo Effect
One positive trait colors our evaluation of a person’s entire character
Bandwagon Effect
We do things because others are doing them
Bystander Effect
The more people present, the less likely any individual will help
Pygmalion Effect
High expectations lead to higher performance
Golem Effect
Low expectations lead to lower performance
Matthew Effect
The rich get richer; the advantaged accumulate more advantage
Hawthorne Effect
People change their behavior when they know they’re being observed
Spotlight Effect
We overestimate how much others notice and remember our actions
Pratfall Effect
A small, human mistake can actually increase perceived attractiveness
Ben Franklin Effect
Doing someone a favor makes you like them more
Mere Exposure Effect
Repeated exposure to something increases our preference for it
Barnum Effect
We accept vague, general descriptions as uniquely accurate portraits of ourselves
In-Group Bias
We favor members of our own group over outsiders
Out-Group Homogeneity Bias
We perceive out-group members as more similar to each other than they are
Dunbar's Number
Humans can maintain only about 150 stable social relationships
Ringelmann Effect
Individual effort decreases as group size increases
Reactance
Being told what to do makes us want to do the opposite
Streisand Effect
Attempting to suppress information causes it to spread more widely
Cobra Effect
A solution makes the original problem worse
Behavioral Economics Effects
Placebo Effect
Believing something works makes it work
Nocebo Effect
Believing something is harmful makes it harmful
Sunk Cost Fallacy
We continue bad decisions because of what we’ve already invested
Loss Aversion
The pain of losing is roughly twice the pleasure of an equivalent gain
Endowment Effect
We overvalue things simply because we own them
Status Quo Bias
We prefer the current state of affairs and resist change
Peak-End Rule
We evaluate experiences by their peak moment and their ending, not the average
IKEA Effect
We place disproportionately high value on things we partially created
Zeigarnik Effect
Uncompleted tasks are remembered better than completed ones
Decoy Effect
A third option changes how we compare the original two
Denomination Effect
Large bills are harder to spend than equivalent small ones
Contrast Effect
Perception shifts based on what we’re comparing against
Choice Overload
Too many options leads to decision paralysis
Butterfly Effect
Small initial differences compound into vastly different outcomes