Date Published: October 4, 2018
Publisher: Public Library of Science
Author(s): Sean Hughes, Simone Mattavelli, Jan De Houwer, José César Perales.
According to a symbolic perspective on EC, pairings constitute a relational contextual cue in the environment. It is the relationship between stimuli as cued by the pairing (i.e., pairings = similar) that determines the observed change in liking. Across five pre-registered studies (N = 747) we manipulated the absolute or relative distance between different pairs of conditioned (CS) and unconditioned stimuli (US) under the assumption that this would influence the type of relation that the pairings would cue (i.e., close = similar; far = different). In all five studies we obtained repeated and strong evidence that stimulus pairings led to changes in implicit and explicit evaluations. Although we found that these effects were moderated by absolute distance manipulations, evidence did not emerge indicating that those same effects were moderated by relative distance manipulations. These findings fail to provide strong support for a symbolic perspective on EC. We discuss the implications of our findings as well as future research in this area.
Evaluative Conditioning (EC) refers to a change in liking due to the pairing of stimuli, and is an important avenue via which evaluations can be established or changed. In a typical EC study a neutral conditioned stimulus (CS) acquires the valence of a positive or negative unconditioned stimulus (US) with which it was previously paired. For example, contiguous presentations of a neutral face with pleasant images can result in that person being evaluated positively whereas pairing the same individual with negative images results in them being evaluated negatively .
Our first experiment set out to investigate if an absolute distance manipulation would moderate the strength of explicit and implicit evaluations. Based on previous work, we anticipated that CS-US pairs presented close together would lead to stronger EC effects than CS-US pairs presented further apart .
In Experiment 2 we sought to demonstrate that EC effects can be moderated via relative distance manipulations. We now exposed participants to two types of EC trials: focal stimulus pairs (presented at a medium distance) and filler stimulus pairs that were (for some participants) presented closer together or (for other participants) presented further apart than the focal pairs. We hypothesized that the first group of participants would view the focal pairs as being relatively closer to one another (and thus more related) when filler pairs were presented at a larger distance. The second group might view the focal pairs as more distant (and thus less related) when the filler pairs were presented closer together. Overall, this should lead to larger implicit and explicit evaluations of the focal stimuli in the former compared to the latter group.
In Experiment 3 we sought to heighten participant’s awareness of the fact that filler and focal stimulus pairs differed in their relative distances, and in so doing, examine if this moderated focal stimulus evaluations. A similar setup was used as in Experiment 2 with three exceptions, all designed to increase awareness of the relative distance manipulation. First, the EC phase was now preceded by instructions indicating that stimuli would be paired, and that in some cases stimuli would be presented close together, whereas in others they would be presented far away from one another (similar to Experiment 1). Second, we presented four rectangles onscreen during each EC trial to emphasize the different location of stimuli (see Fig 3). CSs and USs appeared in two of the four rectangles, depending on whether they were either focal or filler stimuli. Third, we decided to remove the large grey rectangle as this may have undermined our previous distance manipulation.
The relative distance manipulations used in Experiments 2–3 required participants to discern the relative distance between focal and filler CS-US pairs by comparing one type of trial (filler) to another (focal) (i.e., engage in a cross trial-type comparison). In Experiment 4 we sought to make this comparison even easier by making distance changes as salient as possible. Specifically, we now used movement during the filler trials to convey that the distance between CSs and USs was increasing or decreasing, and a lack of movement on the focal trials to signal that no such distance change was taking place (similar to Experiment 1). This time every stimulus started from the same position. Whereas the focal CSs never moved and simply remained static for the duration of the trial, the filler CSs either moved closer together (close condition) or further apart (distant condition). In this way we hoped to increase the probability that people would incorporate distance information when subsequently making a CS evaluation. Once again, our reasoning was that focal CSs should be evaluated more positively or negatively than the filler CSs in the distant condition (given that—in comparison—the focal stimuli are physically closer to each other) and less positively or negatively than the filler CSs in the close condition (given that—in comparison—the focal stimuli are physically more distant to one another).
Upon reflection, the EC phase in Experiments 2–4 confronted participants with two pieces of information: that the CSs and USs were presented contiguously with one another, and that the relative distance between pairs of stimuli could vary. Although instructions highlighted that distance (and not just mere contiguity) was task relevant, the EC phase itself did not require individuals to process the relative distance between stimulus pairs at any point. Indeed, it seems that many participants simply focused on contiguity and ignored distance: in Experiments 2–4 participants registered the contiguity between the CS and US and only sometimes noticed that pairs of stimuli could differ in their relative distance from one another. Thus it may be that relative distance is more likely to moderate EC effects when such information is provided prior to contiguity information than after it.
We recently proposed a new symbolic perspective on EC that draws on the following ideas: that (a) pairings constitute a relational contextual cue in the environment, (b) humans treat this cue as a symbol indicating that the CS and US are related in a certain way, and (c) it is the symbolic relationship between stimuli—established by pairings—which determines the subsequent change in liking. An idea which follows from this perspective is that if one were to manipulate the properties of pairings then this could influence how much pairings function as a symbolic cue—and as a result—influence resulting changes in liking. A core property of pairings is the physical distance between stimuli, and the meaning of distance can potentially be manipulated in two ways. The first (absolute distance manipulations) is simple and direct: it involves just two stimuli that differ in how close or far away they are from one another. The second (relative distance manipulations) is more complex and indirect. It involved two types of trials: focal trials (in which a CS and US were always presented at a medium distance) and filler trials (in which other CSs and USs were presented closer together or further apart). Presenting filler stimuli far away from one another meant that focal stimuli were—by comparison—relatively closer together (and thus could be seen as more similar to one another). Presenting filler stimuli close together meant that the focal stimuli were—by comparison—relatively further apart (and thus might be seen as less similar to one another). If so, then we should observe larger EC effects in the former compared to latter scenario.
Our results lend support to the idea that EC effects can be moderated by manipulating one property of pairings (distance), but only when those manipulations are simple and direct (absolute distance) and less so when they are more complex and indirect (relative distance).