What Is an Ad Biomarker and Why Does It Matter?

Biomarker Category	Advertising Biomarker	Definition	Typical Measurement or Unit	What It Helps Determine	Key Limitation
Exposure Quality	Viewable Impression	An ad impression that meets a recognized viewability threshold rather than merely being served.	Display: at least 50% of pixels visible for at least 1 continuous second. Video: at least 50% of pixels visible for at least 2 continuous seconds, commonly aligned with MRC guidance.	Whether the ad had a reasonable opportunity to be seen.	Viewability does not prove that a person consciously noticed or understood the ad.
Attention	Active Attention Time	The amount of time an ad remains in a viewable state while the user is active on the page or screen.	Seconds of active, viewable exposure per impression or per user.	Whether exposure had enough duration to support message processing.	Longer exposure can result from accidental inactivity and does not necessarily indicate interest.
Interaction	Engagement Rate	The proportion of delivered or viewable ad exposures that generate a defined interaction.	Engagement rate = interactions ÷ eligible impressions × 100. Interactions may include expansion, swipe, sound-on, or completed form actions.	Whether the creative encourages an observable response.	Interaction quality varies, and accidental clicks can inflate the metric.
Message Processing	Brand or Message Recall	The percentage of surveyed respondents who correctly remember an advertised brand, message, or category after exposure.	Unaided recall, aided recall, or correct message recognition measured through a controlled survey.	Whether advertising information was encoded into memory.	Self-reported recall can be affected by questionnaire wording, memory decay, and respondent bias.
Attitude	Brand Lift	The difference in an outcome such as awareness, consideration, or preference between an exposed group and a comparable control group.	Lift = exposed-group response − control-group response, often reported in percentage points or relative percentage change.	Whether advertising changed an attitudinal measure beyond the baseline level.	Results depend on sample quality, control-group comparability, and survey design.
Action	Conversion Rate	The proportion of eligible users or visits that complete a predefined action after an ad exposure.	Conversion rate = conversions ÷ eligible clicks, visits, or users × 100.	Whether advertising is associated with measurable downstream behavior.	Attribution may over-credit the last touchpoint and may not establish causality.
Causality	Incremental Conversion	The additional conversions caused by advertising compared with the conversions expected without advertising.	Incremental conversions = conversions in treatment group − expected conversions in control group.	Whether the campaign created outcomes that would not otherwise have occurred.	Requires a credible randomized or quasi-experimental control design.
Efficiency	Cost per Incremental Action	The advertising cost required to generate one additional action attributable to the campaign.	Cost per incremental action = total campaign cost ÷ incremental actions.	Whether media investment produces economically meaningful additional results.	The result changes substantially with the chosen attribution window and control methodology.
Frequency	Effective Frequency	The number of exposures delivered to a person or defined audience segment during a specified period.	Average frequency = total impressions ÷ unique reached users.	Whether the audience receives enough exposure for reinforcement without excessive repetition.	Average frequency can hide large differences between lightly and heavily exposed users.
Context	Contextual Relevance	The degree to which the content or environment surrounding an ad aligns with the advertised message or audience need.	Content-classification score, category match, sentiment classification, or human-coded relevance rating.	Whether the surrounding context supports comprehension and favorable interpretation.	Automated classification can misinterpret language, sarcasm, or sensitive content.
Privacy and Quality	Consent and Data Provenance	Information describing whether measurement data was collected with an appropriate legal basis and whether its origin and processing history are documented.	Consent status, collection timestamp, source type, processing purpose, retention period, and aggregation level.	Whether the biomarker is suitable for responsible analysis and compliant measurement.	Incomplete consent records or unclear provenance can reduce validity and restrict permitted use.