The science of feedback
About one in three feedback interventions makes performance worse
Kluger, A. N., & DeNisi, A. (1996). The Effects of Feedback Interventions on Performance. Psychological Bulletin, 119(2), 254-284.
The most important fact about feedback is that it is not safely positive. Kluger and DeNisi pooled 607 effect sizes and found that giving feedback lowered performance about a third of the time. The act of telling someone how they did is a coin-flip with a bad edge - the design, not the gesture, decides which way it lands.
Data table
| Segment | Share |
|---|---|
| Improved performance | 62% |
| Reduced performance | 38% |
What they did#
Kluger and DeNisi assembled decades of feedback experiments into a single meta-analysis - 607 effect sizes from 131 studies, spanning classrooms, labs, and workplaces. Instead of asking "does feedback work?" they asked "when does it fail?" - and built Feedback Intervention Theory (FIT) to explain the spread.
Data table
| Item | effect on performance (Cohen's d, schematic direction) |
|---|---|
| Task / process ("your pace sped up") (directs attention to the work) | 0.7 |
| Self ("you are a nervous speaker") (directs attention to the ego) | -0.2 |
What they found#
Feedback helped on average, but the average hid a third of cases where it hurt. FIT's explanation: feedback works by moving your attention. Point it at the task and the gap between where you are and where you want to be becomes useful information. Point it at the self - your worth, your identity, your standing - and attention leaves the task to defend the ego, and performance drops.
The lesson is not "give less feedback." It is "never let the feedback become about the person."
What it means for Speech Away#
Every line our coach writes is aimed at the behavior, never the speaker. "Your pace climbed to ~185 wpm in the last twenty seconds" is task-level and actionable. "You sound nervous" is self-level and corrosive - so the model is explicitly forbidden from saying it. This one rule is why the report can be honest without being discouraging.