Here we offer a brief review of the various studies which throw some useful light on the vexed question of whether longer ads work better.

"Effective Radio Advertising" (Brennecke, 1997): This Dutch study used the method of playing respondents ads down the phone and then (after distraction questions) asking them about memories of the ads. The study concludes that longer ads do have somewhat higher impact, but that spotlength is not as important as position in the break - "to be first in a short block is the goal we should pursue".

Jigsaw Study (Classic FM 1994): This method involved playing radio in the background while respondents were trying to solve a jigsaw, then asking questions about what was remembered. In terms of spotlength, six out the seven best-recalled ads were longer than the conventional 30 seconds. However at the same time, two out of the seven worst-recalled ads were also over 30 seconds. The study notes that style of ad [creativity] appears to be a more significant factor, with four out of five best-recalled using "a dramatic style with a clear narrative or storyline", and six out of the bottom seven using one voice primarily.

Impact Study (Capital Radio 1987): This study used coincidental interviewing, i.e. telephoning people at home after they had been listening to radio - or watching TV, against which results were compared. The average recall for ads over 40 seconds long was calculated as being about 10-15% higher than the average (for both TV and radio). The study concludes that weight of previous advertising activity is a more significant variable than spotlength, as is style of execution.

"Unilever Brand D test" (SIRS/Initiative Media 1994): Unilever ran two comparable campaign patterns on air for this fmcg brand and compared the results. In one area, only 30" ads were run. In the contrast area, 30" and 10" ads were run together. The result was that, while the awareness growth in the areas with solely 30s grew faster, over the course of the campaign (which was sixteen weeks long), awareness in both areas ran to the same level.

The conclusion seems to be that spotlength is not the most important factor, and this soon makes sense when you consider that a creative 10" spot can achieve very high impact.

"Isn’t it a bit like saying a book must be 200 pages long; a symphony has to last for 100 minutes precisely and a poem must be not more (or less) than 50 lines?"   Alastair Crompton, The craft of copywriting