A Direct Comparison of Spatial Attention and Stimulus–Response Compatibility between Mice and Humans

Mice are becoming an increasingly popular model for investigating the neural substrates of visual processing and higher cognitive functions. To validate the translation of mouse visual attention and sensorimotor processing to humans, we compared their performance in the same visual task. Mice and human participants judged the orientation of a grating presented on either the right or left side in the visual field. To induce shifts of spatial attention, we varied the stimulus probability on each side. As expected, human participants showed faster RTs and a higher accuracy for the side with a higher probability, a well-established effect of visual attention. The attentional effect was only present in mice when their response was slow. Although the task demanded a judgment of grating orientation, the accuracy of the mice was strongly affected by whether the side of the stimulus corresponded to the side of the behavioral response. This stimulus–response compatibility (Simon) effect was much weaker in humans and only significant for their fastest responses. Both species exhibited a speed–accuracy trade-off in their responses, because slower responses were more accurate than faster responses. We found that mice typically respond very fast, which contributes to the stronger stimulus–response compatibility and weaker attentional effects, which were only apparent in the trials with slowest responses. Humans responded slower and had stronger attentional effects, combined with a weak influence of stimulus–response compatibility, which was only apparent in trials with fast responses. We conclude that spatial attention and stimulus–response compatibility influence the responses of humans and mice but that strategy differences between species determine the dominance of these effects.

Sense and Sensitivity – Using Spatial Response-Compatibility Effects to Investigate Ambiguous Word Meaning

We investigated sensitivity for the vertical meaning of the German particle ab by means of stimulus–response compatibility effects. In German, the particle ab is ambiguous and can take on a vertical meaning (downward) as in Auf und Ab (engl. up and down), but it can also take on nonvertical or nonspatial meanings as in Ab und An (engl. from time to time). We show that the particle ab only creates a spatial compatibility effect relative to the German particle auf (Experiment 1) but not relative to the particle an (Experiment 2). Furthermore, as participants executed upward versus downward responses in both Experiments 1 and 2, the mere vertical antagonism of the responses was insufficient to instill a verticality-based compatibility effect. In addition, the compatibility effect was restricted to the transparent version of the particle. If a letter sequence corresponding to the particles was presented in a semantically and morphologically opaque way (e.g., the letters ab were embedded in the German word kn ab e, engl. boy), no compatibility effect was found, underlining that the effect was due to word meanings rather than visual features. The results underscore the boundary conditions for using compatibility effects in investigating lexical and semantic spatial processing in humans.

Spatial–numerical associations in the presence of an avatar

When we interact with other people or avatars, they often provide an alternative spatial frame of reference compared to our own. Previous studies introduced avatars into stimulus–response compatibility tasks and demonstrated compatibility effects as if the participant was viewing the task from the avatar’s point of view. However, the origin of this effect of perspective taking remained unclear. To distinguish changes in stimulus coding from changes in response coding, caused by the avatar, two experiments were conducted that combined a SNARC task and a spontaneous visual perspective taking task to specify the role of response coding. We observed compatibility effects that were based on the avatar’s perspective rather than the participants’ own. Because number magnitude was independent of the avatar’s perspective, the observed changes in compatibility caused by different perspectives indicate changes in response coding. These changes in response coding are only significant when they are accompanied by visual action effects.

Disentangling stimulus and response compatibility as potential sources of backward crosstalk

In two experiments (N= 60 each), we investigated the locus of backward crosstalk effects in dual tasking. Specifically, we embedded the typical flanker task within a dual-task paradigm by assigning stimulus-response (S-R) rules to the flankers. In Experiment 1, participants were instructed to first respond to the center letter and only respond to the flanker if the center was a no-go stimulus (i.e., prioritized processing paradigm). Mapping condition was varied between-subjects to be either matched (i.e., same S-R rule for flankers as for center letters), reversed (i.e., opposite S-R rule for flankers), or neutral (i.e., different letters for flankers with separate S-R rules). The results indicated that the backward crosstalk effect was mainly driven by a stimulus-based compatibility, as indicated by a significant S2−R1 compatibility effect in the matched and reversed conditions, with little change in this effect between the matched and reversed conditions. Experiment 2 replicated and extended these findings to a psychological refractory period paradigm. The present findings suggest that in the matched and reversed conditions, there was only one S-R rule active at a time.