Confirmation bias causes engineers to hear what they expect a processing change to do rather than what it actually does

Confirmation bias is a psychological tendency to perceive what we expect rather than what is objectively present. In a mix context, when an engineer applies a plug-in expecting improvement, they will often perceive an improvement regardless of whether one exists. This explains the common experience of tweaking a processor for several minutes only to discover it was bypassed the whole time. To counteract this, use blind comparison: hover over the bypass button, close eyes, toggle the button to an unknown state, then assess the sound before looking at the screen. ABX testing software formalizes this process for conclusive results.

Examples

Engineer adds a ‘vintage tape’ plugin expecting warmth; blind A/B test reveals no audible difference. The expected improvement was entirely due to confirmation bias.

Assessment

Explain what confirmation bias is and give a specific example of how it can mislead an engineer during mixing. Describe one technique to counteract it.