The action-specific effect of execution on imagination of reciprocal aiming movements.

Past research has shown that the movement times of imagined aiming movements were more similar to actual movement times after the individual has experienced executing the movements. The purpose of the present study was to determine if experience with a set of movements altered the imagination of movements that were not experienced. Participants imagined a series of reciprocal aiming movements in different movement difficulty contexts (created by altering target width and movement amplitude) before and after actually executing a series of aiming movements. The range of difficulties of the imagined movements included difficulty contexts that were within (Experiment 1) or outside (Experiment 2) the range of difficulty experienced during execution. It was found that imagined movement times of movements within the range of movement difficulties experienced were more consistent with Fitts' Law after movement experience, whereas imagination of more difficult movements was not altered by experience. It is suggested that execution did not enhance imagination of more difficult movements because the relative contributions of motor planning and control to the more difficult movements were different from those in the experienced movements. Thus, the enhancement of imagination through experience might only occur when mechanisms underlying the executed and imagined movements are similar.

Embodying animals: Body-part compatibility in mammalian, reptile and aves classes.

The purpose of the present study was to determine how humans code homologous body parts of nonhuman mammal, reptilian, and aves animals with respect to the representation of the human body. To this end, participants completed body-part compatibility tasks in which responses were executed to colored targets that were superimposed over the upper limbs, lower limbs or head of different animals in different postures. In Experiment 1, the images were of meekats and lizards in bipedal and quadrupedal postures. In Experiment 2, the images were of a human, a penguin, and an owl in a bipedal posture with upper limbs stretched out. Overall, the results revealed that the limbs of nonhuman mammals (meerkat and human) were consistently mapped onto the homologous human body parts only when the mammals were in a bipedal posture. Specifically, body-part compatibility effects emerged for the human and the meerkat in a bipedal posture, but not the meerkat in the quadrupedal posture. Further, consistent body-part compatibility effects were not observed for the lizard in the quadrupedal posture or for the lizard, penguin, or owl in a bipedal posture. The pattern of results suggests that the human bipedal body representation may distinguish taxonomical classes and is most highly engaged when viewing homologous body parts of mammalian animals.

Trajectory deviations in spatial compatibility tasks with peripheral and central stimuli.

It is widely held that the spatial compatibility effect emerges because the irrelevant spatial dimension of the target stimulus activates a response simultaneous to the activation of a response to the relevant stimulus dimension. The non-target response facilitates response planning on compatible trials, but interferes with response planning on incompatible trials. In support of this hypothesis, the trajectories of aiming movements executed on incompatible trials deviate in the direction of the stimulus location. These deviations are thought to occur because the characteristics of the simultaneously active target and non-target responses merge. Previously, target stimuli were presented at the target locations leaving open the possibility that the response activation and subsequent deviations were dependent on the stimulus-driven attentional capture associated with the dynamic change of stimulus onset. The present research was conducted to determine if attention capturing events at the target locations were necessary for the movement deviations to emerge by investigating if trajectory deviations are also observed when the spatial dimension is presented centrally. Participants in the Central condition aimed to left and right target locations based on the color of a ring worn on a finger that pointed toward the response locations. Similar to results from a Peripheral condition, trajectory deviations were observed in the Central condition. Although it is unclear if the deviations in the Central condition occurred because of attentional shifts driven by the cue or response preplanning, these results demonstrate that dynamic changes at target locations are sufficient, but not necessary, to generate trajectory deviations.