Approach and avoidance beyond verbal measures: A quantitative meta-analysis of human conditioned place preference studies.

Adaptive approach and avoidance in responses to reward and threat are fundamental to prevent harm and to ensure well-being. In contrast, maladaptive approach or avoidance behavior likely contributes to anxiety or substance abuse disorders, respectively. Therefore, there is a need to assess such behavior in humans objectively. Conditioned place preference (CPP) is a well-established animal paradigm investigating approach-avoidance mechanisms, i.e., context-associated appetitive/aversive effects of unconditioned stimuli. Recently, the retranslation of this paradigm for human research started. This meta-analysis provides the first systematic overview of this developing field. A total of 17 studies published before June 2020 fulfil our inclusion criteria: (1) Usage of a rewarding agent, (2) implementation of either virtual or real environments, (3) human subjects, and (4) report of standardized outcome measures. These studies were evaluated and analyzed following the DIAD model and the PRISMA guidelines, respectively, and specific subanalyses were preformed to identify modulating factors of CPP effects (e.g., Virtual Reality applications, biased/unbiased). Overall, a significant medium effect size for the behavioral measure of dwell time (g =.62, p < .001, 95%-CI =.43-.81) and a significant small effect size for verbal self-ratings (g =.33, p < .001, 95%-CI =.04-.63) were observed, although across-study results were characterized by substantial heterogeneity (l2 > 65%). These results indicate great potential for CPP to study approach-avoidance behavior in humans, directly in analogy to animal studies. We provide guidelines for future CPP research to improve comparability of studies and to facilitate new insights into anxiety disorders and drug abuse.

Remapping motion across modalities: tactile rotations influence visual motion judgments.

Multisensory interactions between haptics and vision remain poorly understood. Previous studies have shown that shapes, such as letters of the alphabet, when drawn on the skin, are differently perceived dependent upon which body part is stimulated and on how the stimulated body part, such as the hand, is positioned. Another line of research within this area has investigated multisensory interactions. Tactile perceptions, for example, have the potential to disambiguate visually perceived information. While the former studies focused on explicit reports about tactile perception, the latter studies relied on fully aligned multisensory stimulus dimensions. In this study, we investigated to what extent rotating tactile stimulations on the hand affect directional visual motion judgments implicitly and without any spatial stimulus alignment. We show that directional tactile cues and ambiguous visual motion cues are integrated, thus biasing the judgment of visually perceived motion. We further show that the direction of the tactile influence depends on the position and orientation of the stimulated part of the hand relative to a head-centered frame of reference. Finally, we also show that the time course of the cue integration is very versatile. Overall, the results imply immediate directional cue integration within a head-centered frame of reference.