Do your movements have a “mind” of their own? When watching leads to unintended doing

Many movements we perform on a daily basis are preplanned in our brains well before we intend to execute them. For example, when a sprinter takes the blocks in a race, they have a very good idea of what movements they need to produce when the starting signal is heard. If this starting sound is above a certain level (124 dB) it may elicit what is called a startle response. This startle response is not only very fast, but if a movement has been prepared in advance, when startled, the response that comes out is pretty much the prepared response coupled with some startle indicators (such as clenching of the neck & facial muscles). In this study, we provided evidence that even observed and imagined actions can be (partially) ‘released’ when a person is startled, even though there is no intention to act. This suggests that these type of covert actions may be  prepared in a similar way to actual movements. 

As protocol, we used a simple key lift reaction time test. Trials were conducted with two individuals facing each other. People practiced lifting their fingers in response to a tone. They also just observed their partner or just imagined performing the finger lift. We measured muscle activation patterns, a change in force on the key, as well as the frequency of actual finger lifts. As expected, in response to a loud startle tone, when participants were told to move, a full response was seen (just much faster than to a normal tone). In the imagery trials and somewhat less so in the observed trials, no actual finger lifts were seen. However, what we termed “partial responses” were noted in these conditions, even though participants were not instructed to move. This was evidenced by a decrease in force exerted on the key and increased muscle activation, actions that would precede a full response. This was interesting to see and suggests that both actual and covert actions are prepared, even though only in the former is an actual response required.

The results of this study lead us to believe that both observation and imagery conditions lead to movement preparation at a sub-threshold level, but that these can “leak out” when activation is increased by the presence of a loud, startle tone. Therefore, even when we are watching others perform actions that we have just performed, or we are imagining ourselves moving, we are still actually ‘preparing’ to move ourselves.

Do your movements have a “mind” of their own? When watching leads to unintended doing

Many movements we perform on a daily basis are preplanned in our brains well before we intend to execute them. For example, when a sprinter takes the blocks in a race, they have a very good idea of what movements they need to produce when the starting signal is heard. If this starting sound is above a certain level (124 dB) it may elicit what is called a startle response. This startle response is not only very fast, but if a movement has been prepared in advance, when startled, the response that comes out is pretty much the prepared response coupled with some startle indicators (such as clenching of the neck & facial muscles). In this study, we provided evidence that even observed and imagined actions can be (partially) ‘released’ when a person is startled, even though there is no intention to act. This suggests that these type of covert actions may be  prepared in a similar way to actual movements. 

As protocol, we used a simple key lift reaction time test. Trials were conducted with two individuals facing each other. People practiced lifting their fingers in response to a tone. They also just observed their partner or just imagined performing the finger lift. We measured muscle activation patterns, a change in force on the key, as well as the frequency of actual finger lifts. As expected, in response to a loud startle tone, when participants were told to move, a full response was seen (just much faster than to a normal tone). In the imagery trials and somewhat less so in the observed trials, no actual finger lifts were seen. However, what we termed “partial responses” were noted in these conditions, even though participants were not instructed to move. This was evidenced by a decrease in force exerted on the key and increased muscle activation, actions that would precede a full response. This was interesting to see and suggests that both actual and covert actions are prepared, even though only in the former is an actual response required.

The results of this study lead us to believe that both observation and imagery conditions lead to movement preparation at a sub-threshold level, but that these can “leak out” when activation is increased by the presence of a loud, startle tone. Therefore, even when we are watching others perform actions that we have just performed, or we are imagining ourselves moving, we are still actually ‘preparing’ to move ourselves.