Seeing Then, Remembering Later: Testing Repetition's Effect on Liking

Does failing to remember a shape prove that you never noticed it when it appeared? Everyday conversation easily substitutes one claim for the other. Yet a forgotten encounter and a presentation outside conscious awareness are not identical events. The distinction matters when investigating whether repetition makes something more pleasant. If recognition subsequently fails, an increase in liking cannot automatically be treated as evidence that an unseen stimulus changed a preference. Two measurements separated in time may have been confused.

A 2013 study by Daniel de Zilva and colleagues put this problem at the center of its design. The researchers varied visibility while holding presentation duration constant and asked participants about awareness after every exposure. The investigation therefore concerned not only whether repetition increased liking, but also how an apparently unseen presentation qualified as unseen. Its two experiments, and especially their direct comparisons, need to be followed separately. [1]

Different information for the two eyes

The method was continuous flash suppression. A target contour appeared to one eye while rapidly changing visual-noise patterns appeared to the other. The noise could suppress conscious visibility of the target. In the visible condition, the target was also superimposed on the noise shown to the other eye. Both conditions consequently contained dynamic noise; the comparison was not simply between a noisy presentation and an otherwise clean image. [1]

Red-and-green filter glasses separated the screen's color-channel information between the eyes. Each presentation lasted one second. Keeping duration equal reduced the problem of comparing a briefly shown stimulus with a longer presentation and assigning every difference to awareness. It did not make this the only possible manipulation of awareness or guarantee identical results with other suppression methods. [1]

After each exposure, the participant reported whether a contour had been seen. Catch trials contained noise without a target, helping identify people who repeatedly reported a contour when none was present. These trials did not equally establish whether someone used an overly conservative criterion and denied a partial visual experience. The researchers explicitly acknowledged this limitation of their subjective awareness measure. [1]

The first test used contours

Experiment 1 recruited a convenience sample of 1,005 introductory psychology students as part of a classroom demonstration. Sixteen meaningless contours were assigned to exposure frequencies of zero, one, ten, or twenty. Zero exposure supplied novel items for comparison at test. Pleasantness and recognition were subsequently rated in separate tests on seven-point scales. Finding a contour pleasant and reporting that it had been seen before were different judgments. [1]

The recruitment total was not the sample size of every analysis. Catch-trial performance and awareness reports led to exclusions. If a supposedly suppressed contour was reported as seen on any exposure, that contour's data were removed. Data were likewise excluded when a contour intended to be visible was reported as unseen. The analysis thus did not merely assume that an assigned condition perfectly described a person's experience. These exclusions also left unequal numbers of participants with complete data in the two conditions. [1]

For visible contours, pleasantness showed a small increase with exposure frequency. Suppressed contours did not show such an increase. Crucially, however, the direct comparison using participants with complete data in both conditions did not reveal a significant interaction between awareness and exposure frequency. One significant trend and one nonsignificant trend do not, by themselves, demonstrate a significant difference between trends. Experiment 1 alone therefore did not support a strong conclusion about awareness. [1]

A more discriminable target

The researchers replaced contours with faces in Experiment 2. They proposed that easier-to-distinguish targets might produce a clearer repetition effect. This was a hypothesis tested with different material, not a definitive explanation already established by the first result. The second experiment recruited 240 psychology students who had not participated in the first. [1]

Faces had neutral, happy, or angry expressions. Each participant was randomly assigned to one expression condition; individuals did not experience all three expressions. Exposure frequency and visible versus suppressed presentations remained parts of the design. The same awareness and catch-trial exclusions were applied. Only sixty-five participants had complete data across both visibility conditions and all exposure frequencies for the matched comparison. It would be incorrect to describe that particular analysis as involving all 240 recruits. [1]

This time, the matched data showed a significant interaction between exposure frequency and awareness. Repetition increased pleasantness for visible faces, while no reliable increase appeared for suppressed faces. Recognition also increased for visible presentations without showing the corresponding pattern under suppression. Visible repetition had a larger liking effect for neutral expressions than for the other expressions. The result cannot be reduced to happy faces simply being more pleasant at the outset. [1]

The face experiment thus supplied a comparison that the contour experiment had not established reliably. Preserving that difference is important. Treating both experiments as equally decisive would hide the reason the second test was informative and make the evidence seem more uniform than it was.

What an absent effect does not establish

The finding did not demonstrate that suppressed targets received no mental processing. The researchers did not collect brain images in these experiments. What level of processing survived suppression remained an open interpretive question in their discussion. If the method also strongly limited higher-level processing, the absence of increased liking might not have an explanation specific to absent awareness alone. [1]

The evidence consequently need not be expanded into a claim that every unconscious influence is impossible or that every form of subliminal advertising must be ineffective. Differences between earlier brief-masking results and the present suppression method were not declared conclusively resolved. The narrower conclusion is more defensible: with this equal-duration suppression procedure, repeated targets that remained outside reported awareness did not acquire a reliable liking advantage. [1]

There is also a practical methodological tradeoff in measuring awareness. Asking a participant to choose between exposed and new targets after each trial could supply another exposure and contaminate later pleasantness tests. The authors' reliance on seen-or-unseen reports therefore reflected competing measurement concerns, even though those reports retained limitations. A better measure in one respect can alter the very experience another measure is meant to assess. [1]

The lasting lesson is to preserve three distinct observations: seeing reported during presentation, recognition judged afterward, and pleasantness rated afterward. They can change together without becoming interchangeable. Following the less decisive contour comparison into the clearer face experiment produces a more useful account than a sweeping headline about hidden influence. Understanding how liking changes begins with understanding how the encounter itself was measured.

Sources

[1] de Zilva, D., Vu, L., Newell, B. R., and Pearson, J. (2013). Exposure Is Not Enough: Suppressing Stimuli from Awareness Can Abolish the Mere Exposure Effect. PLOS ONE, 8(10), e77726. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0077726 . DOI: 10.1371/journal.pone.0077726. Independently written explanation of research published under a Creative Commons Attribution license.