Pointing hand stimuli induce spatial compatibility effects and effector priming

Investigating Object Affordance in People with Complex Regional Pain Syndrome: No Alterations in the Automatic Activation of Motor Plans

Complex Regional Pain Syndrome (CRPS) is a condition of chronic pain, predominantly affecting one limb. CRPS is characterised by motor changes including slowed or uncoordinated movements. Cognitive processes that drive movement planning and/or execution might contribute to these changes. We aimed to investigate the potential alterations to such cognitive mechanisms using an 'object affordance' paradigm. Object affordance refers to the observation that viewing an object modulates associated motor responses, presumably due to the automatic activation of a motor plan. We hypothesised that people with CRPS would show reduced object affordance effects for their affected compared to unaffected hand, and compared to pain-free controls. First, we validated an online object affordance task involving button press responses to everyday objects with handles, in pain-free participants (n = 63; Experiment 1). Object affordance was reflected by faster and more accurate responses when the object handle was aligned to the responding hand ("aligned") compared to when the handle was aligned to the other hand ("non-aligned"). These results were similar for the online task as when administered in person. Second, in a case-control study, we administered the online object affordance task to people with CRPS predominantly affecting the upper limb (n = 25), and age-matched pain-free controls (n = 68; Experiment 2). People with CRPS responded faster and more accurately in the aligned versus non-aligned condition (ie, an object affordance effect), both for the affected and unaffected hands. There were no differences to pain-free participants. Therefore, object affordance effects were seen in people with CRPS, providing no evidence for altered motor planning. PERSPECTIVE: This article presents research investigating cognitive processes related to motor planning in Complex Regional Pain Syndrome (CRPS). Using an online object affordance paradigm, validated in pain-free controls, the authors found that people with CRPS showed intact object affordance effects in the affected and unaffected hand, suggesting unaltered motor planning. DATA AVAILABILITY: The experiment materials, data, pre-processing scripts, and analysis scripts can be found via Open Science Framework (https://osf.io/nc825/files/osfstorage).

What's the point? Infants' and adults' perception of different pointing gestures

Adults and infants as young as 4 months old orient to pointing gestures. Although adults are shown to orient faster to index-finger pointing than other hand shapes, it is unknown whether hand shapes influence infants' perception of pointing. In this study, we used a spatial cueing paradigm on an eye tracker to investigate whether and to what extent adults and 12-month-old infants orient their attention in the direction of pointing gestures with different hand shapes: index finger, whole hand, and pinky finger. Furthermore, we assessed infants' and their parents' pointing production. Results revealed that adults showed a reliable cueing effect: shorter saccadic reaction times (SRTs) to congruent than incongruent targets, for all hand shapes. However, they did not show a larger cueing effect triggered by the index or any other finger. This contradicts previous findings and is discussed with respect to the differences in methodology. Infants showed a cueing effect only for the whole hand but not for the index or pinky fingers. The current results suggest that infants' orienting to pointing may be more robust for the whole hand shape in the first year, and tuning in to the social-communicative relevance of the canonical index finger shape may develop later or require additional social-communicative cues.

Hand, but not foot, cues generate increases in salience at the pointed-at location

One line of research has indicated that directional social cues, such as eye gaze and pointed fingers, increase the salience of spatial locations or objects in a relatively involuntary manner (social cueing effect). A separate line of research has indicated that the compatibility between the body part that is observed by an actor primes and facilitates responses with a similar body part more than a dissimilar body part (body-part compatibility effect). The present experiment investigated whether or not social cueing effects were modulated by the relationship between the responding effector and the body part observed as the cue. To this end, non-predictive directional hand or foot cues were presented 100 or 1000 ms prior to a target. On different blocks of trials, participants (n = 19) executed discrete hand-button and foot-pedal responses to the location of a target to examine the influence of cue-effector body-part compatibility on social cueing effects. Response times (RTs) of both hand and foot responses were shorter to cued targets than to uncued targets when hand cues were used. No cueing effects emerged when foot cues were used, regardless of the responding effector. These results suggest changes in salience following social cues are determined by the body part used as the cue and are not modulated by the compatibility between the limb used as the cue and effector. Overall, the social relevance and learned use of a cue seem more pertinent than body-part matching of a stimulus type and response effector in social cueing.

Can sign language make you better at hand processing?

The languages developed by deaf communities are unique for using visual signs produced by the hand. In the present study, we explored the cognitive effects of employing the hand as articulator. We focused on the arbitrariness of the form-meaning relationship—a fundamental feature of natural languages—and asked whether sign languages change the processing of arbitrary non-linguistic stimulus-response (S-R) associations involving the hand. This was tested using the Simon effect, which specifically requires such type of associations. Differences between signers and speakers (non-signers) only appeared in the Simon task when hand stimuli were shown. Response-time analyses revealed that the distinctiveness of signers’ responses derived from an increased ability to process memory traces of arbitrary S-R pairs related to the hand. These results shed light on the interplay between language and cognition as well as on the effects of sign language acquisition.