The goal of this work was to investigate whether autistic adults can engage in explicit MI, and how MI processes relate to action execution and perception both in autistic and non-autistic individuals. This study is the first to employ the Fitts’ Law paradigm across execution, imagination, and perception tasks and to test explicit MI with mental chronometry in autistic individuals. Fitts’ Law relationships were observed in both groups across all three tasks. Subsequent mixed ANOVA analysis showed longer MTs for the imagination task and the most difficult level (highest ID) and shorter MTs for the perception task and easiest level (lowest ID) across both groups. A three-way interaction among Group, Task, and Difficulty Level (ID) was observed, indicating a steeper slope as the index of difficulty increased from easy to medium level for the perceptual compared to imagination task within the autistic group. In sum, these data provide evidence that action imagination is relatively intact in autistic individuals.
The current study built upon 54 by comparing executed, perceived, and imagined MTs in a Fitts’ Law paradigm and extending it to include both autistic and non-autistic groups. Consistent with Wong et al.’s54 findings, our study demonstrated a similar Fitts’ Law relationship across all three tasks for both groups, with MTs increasing as the ID levels increased. Despite observing variability among participants, our data showed similar patterns of performance at the individual level across both groups. Importantly, this replication supports the use of the Fitts’ Law paradigm in an online environment. These results are consistent with the common coding hypothesis, which posits that action execution, perception, and imagination are related through shared, abstract neural codes, that facilitate a bidirectional response that enables individuals to interact with their environment appropriately12,14.
The ANOVA analysis revealed a significant main effect for Task. The imagination task resulted in the longest MTs for both groups, corroborating Wong et al.’s54 findings. In line with Glover et al.’s56 proposition, the extended MTs in imagination tasks may be attributed to the additional cognitive load required to maintain imagined movements, which involves working memory demands19,65. This conclusion is further supported by neural activation patterns, where the dorsolateral prefrontal cortex, a region implicated in movement inhibition, is recruited during motor imagination but not during action execution or perception. This activation may underlie the increased effort to suppress actual movement during imagination19,66.
A significant three-way interaction between Group, Task, and ID was also observed; an interaction driven by the Task and ID effects within the autistic group. The autistic group displayed a more pronounced increase in movement duration between ID 1 and 2 for perception tasks relative to execution tasks. This discrepancy indicates that, in comparison to referencing actual movements, the autistic group may utilize alternative strategies or cognitive processes for completing perception tasks, echoing the suggestions of previous studies9,41,43,47. Nonetheless, caution should be exercised when interpreting these results due to their unpredicted nature and the potential influence of group characteristics, such as SRS-2 and ADC scores. These measures, which assess social ability and motor coordination, may partially explain the observed group differences. When these scores were accounted for as covariates, the interaction effects in Fitts’ task performance disappeared, indicating that autistic and motor characteristics might influence performance in perception and imagination tasks.
The overarching findings of similarities in performance between the autistic and non-autistic group for the perception and execution tasks is consistent with literature indicating that autistic individuals have comparable capabilities in movement speed perception tasks21,67,68 and Fitts’ Law relationship for simple hand aiming movements57. The current study utilized mental chronometry to assess explicit MI, and despite lower ADC scores, individuals with autism exhibited proficiency in the imagination task. Previous research exploring explicit MI in autism, using self-reported questionnaires or experimental tasks, has yielded mixed results9,46–48. The current study contributes new findings in this domain by employing both questionnaires and behavioural measures. Earlier investigations into explicit MI in autistic adults suggested a discrepancy in their ability to use MI. For instance, a study using a spatial bimanual task, where participants drew a line with their right hand while imagining drawing a circle with their left hand, found that autistic individuals were unaffected by the imagination condition during dual tasks, unlike the non-autistic individuals47. Another study reported that autistic individuals did not benefit from imagining a sequence in a sequence recall task compared to a matched group48. However, the current study observed a similar Fitts’ Law relationship in both groups for the imagination task. The disparity could be attributed to the simplicity of our task design, requiring participants to focus solely on the MI, without engaging in higher cognitive processes such as remembering sequences or performing a concurrent task. Alternatively, a limitation of the previous studies (see47,48) is that it is unclear whether autistic individuals were actually using MI and they did not need to use it to complete the tasks. In contrast, MI is more central and “less optional” in chronometry tasks, as participants are asked to report the duration of the imagined movement. This study may have encouraged the use of MI in the Fitts’ Law task. Another potential reason is the exclusive use of MT as a measure in our study, which had reduced accuracy due to the online nature of conducting the experiment.
Moreover, in contrast to the Fitts’ tasks performance, significant group differences were found in both the VI and KI subscales of the KVIQ, with the autistic group reporting less vivid imagery. This result contrasts with a study using the same questionnaire but finding no significant differences between autistic and non-autistic groups46. One potential explanation for this discrepancy may relate to the version of the KVIQ used in the studies. The current study utilized a video-recorded short version (5-item) of the KVIQ, whereas Gowen et al.46 employed an in-person full version. In the in-person setting, having participants sit side by side with the experimenter may have been more conducive to facilitating MI, as opposed to the online version where movements were demonstrated in a third-person perspective. Some participants in the current study reported that they could only imagine the actor in the video performing the movements, rather than visualizing themselves executing the tasks63. This difference in perspective could significantly impact how participants engage with and perform in MI tasks.
Comparing the imagination results from the Fitts’ task and KVIQ questionnaire, the different results may also be due to the different focus: the Fitts’ task measures relatively objective MT, while the KVIQ assesses subjective experiences on a 5-point scale, probing the vividness and intensity of imagined movements. These differing methodologies assess different aspects of MI, with the self-reported KVIQ focusing more on how participants generate motor images, and the Fitts’ task emphasizing the ability to maintain motor images69. Meanwhile, participants may utilize alternative strategies during the imagination task, such as moving their eyes between targets (such eye movements were anecdotally observed by the researcher, but not recorded during the experiment). However, participants may be less able to employ such eye movement strategies in the KVIQ, resulting in lower reported vividness or intensity. Further studies could explore if autistic individuals can demonstrate MI when asked to not move their eyes (note that restricting eye movements impacted imagined MTs in non-autistic individuals70). Additionally, autistic individuals might express their internal experiences less proficiently or exhibit increased caution when responding to subjective scales71,72. A further reason for the divergent findings may be the different movements involved in each task. The KVIQ includes a variety of movements, such as lifting an arm, bending the upper body, or lifting a leg, whereas the imagination task in our study involved only the dominant hand in an aiming task. These mixed results suggest that while autistic individuals may be adept at simple movements, they may struggle with more complex tasks and potentially employ different strategies compared to non-autistic individuals4,63. Finally, it is important to acknowledge individual differences in MI ability; when KVIQ scores were considered as a covariate, they did not significantly alter performance on Fitts’ task. This indicates that MI ability may consistently affect individuals’ performance regardless of the task type.
Our study’s findings suggest that individuals with autism are capable of effectively utilizing MI. This discovery opens the door for the application of MI as a therapeutic intervention as demonstrated and used in Developmental Coordination Disorder73, Parkinson’s disease74,75, and post stroke76, which could potentially enhance the performance of daily life tasks in autistic individuals. Such interventions could be tailored to leverage the strengths in MI that this group exhibits, thus offering practical benefits in skills training and rehabilitation.
Although our study successfully replicated the findings of Fitts’ tasks in non-autistic groups, conducting the experiment in an online setting introduced certain limitations. The lack of kinematic data collection of the actual hand movements during execution and imagination meant that our analysis was confined to movement time, excluding other crucial aspects of motor performance. Previous work has explored additional non-goal hand movements (motor overflow) during imagination and found that these movements increased as the amplitude of the imagined movements increased54,70. Additionally, participants needed to have access to internet and a certain comfort level with computers and one-on-one interactions with the experimenter, and as such the autistic individuals who chose to volunteer for the study were relatively young and verbal. Future research in a controlled laboratory environment would enable more comprehensive data collection, including metrics such as movement accuracy and smoothness, and motor overflow. Introducing more complex tasks in future studies could also provide deeper insights into whether the observed performance equivalence between autistic and non-autistic individuals persists under more demanding conditions.
Due to the constraints of our study’s settings and procedures, we were unable to thoroughly investigate the specific strategies employed by individuals during the tasks. The exploration of these personal MI strategies and their impact on task performance remains a significant area for future research. It is particularly important to investigate the alternative strategies that autistic individuals might use during MI tasks (e.g., counting, moving eyes, small finger movements, etc.)63. Understanding these strategies could be instrumental in developing MI-based interventions tailored to improve motor functions in individuals with autism, potentially leading to innovative therapeutic approaches that leverage the unique cognitive profiles of this population.
In conclusion, the current study has demonstrated that individuals with autism can complete Fitts’ Law tasks and effectively engage in explicit MI. These findings open potential avenues for MI-based therapeutic interventions to improve their daily life. Further research should delve deeper into explicit MI strategies used in autism, particularly in more controlled experimental settings, to validate these findings and refine the intervention.