Alexithymia was first introduced in the field of psychosomatic medicine and has recently been referred to as a personality trait characterized by a deficiency in the cognitive processing of emotions, namely, difficulties in identifying and communicating emotions, and externally-oriented thinking 
. These characteristics reflect a disruption in the conscious experience of emotions 
. Voluntary control, as an important aspect of consciousness and the source of attention, is critical for regulating mental computations including emotional processes. 
. However, this supervisory system is possibly severely impaired in individuals with high alexithymia 
. In addition to difficulties in recognizing and expressing emotions, these individuals often manifest flattened emotions at default, yet accompanied by random and abrupt emotional outbursts which they cannot interpret; they also have overcontrol of their internal needs, an exaggerated defensive system, and dysregulated autonomic responses such as increased heart rate to emotion-evoking stimuli, although always report less emotional experiences 
. All these manifestations indicate a disconnection between the physiological responses and the voluntary control of emotions in alexithymia.
The notion that alexithymic trait is associated with voluntary control is derived from the aforementioned findings from psychosomatic medicine, and has been supported by experimental psychology studies carried out in nonclinical samples as well as neuroimaging findings. Behavioral studies have reported that alexithymic individuals are impaired in the cognitive processing of emotions 
. One study used both the 20-item Toronto Alexithymia Scale (TAS-20) and the Level of Emotional Awareness Scale (LEAS) to assess alexithymic trait in a community sample of 380 subjects 
, and the participants were asked to identify emotions in a Perception of Affect Task (PAT). People with higher alexithymia scores had a decreased ability of recognizing both verbal and nonverbal emotions. Another study found that healthy adults with higher TAS-20 scores showed a diminished priming effect from contextual information to emotional words 
. In other words, the presentation of an emotional context facilitated the processing of a related emotional word in a lesser extent in people with higher alexithymia scores than those with lower alexithymia scores. These studies clearly demonstrated that alexithymic trait is associated with the ability of the cognitive processing of emotions. As is mentioned before, although the top-down control of physiological responses are disrupted, autonomic responses per se
are not impaired in people with high alexithymia 
. Therefore, alexithymia is viewed as “blindfeel”, the emotional equivalent of blindsight 
. According to this thesis, alexithymia is a deficit in reaching the conscious awareness and in maintaining the voluntary control of emotions, rather than a disruption in the sensory/perceptual aspect of emotions. Alexithymic individuals can be emotionally aroused just as much as non-alexithymic individuals; however, they would report they do not feel anything or do not know how they feel, and consequently can not regulate their emotional states.
Neuroimaging studies have further supported this view by revealing that alexithymic trait is associated with a common neural substrate subserving voluntary control. Voluntary control is known to be implemented by a brain network including the anterior cingulate cortex (ACC), and other frontoparietal regions 
. The ACC subserves a wide range of high-level functions including executive control, error detection, reward, anticipation, and consciousness 
. The ACC is consistently activated in situations where competing information needs to be processed 
. When the ACC is lesioned, executive control is likely to be affected, although this is not always the case 
. On the other hand, accumulating evidence also suggests that the ACC is associated with overall reaction time (RT) in cognitive tasks, which represents the general efficiency of voluntary control. fMRI and PET studies have reported that the amplitude of ACC activation changes as a function of RTs in various cognitive tasks 
. Decreased ACC volumes are associated with longer RTs in cognitive tasks where controlled processes are required 
. Indeed patients with focal ACC lesion have slower response speed during cognitive tasks 
. We expect that a normal individual with a less efficient ACC, in that case, would also have diminished executive control, or slower response speed in cognitively challenging tasks, or both.
Interestingly, a deficiency in the ACC is indeed evident in alexithymic individuals 
. In a positron emission tomography (PET) study by Lane and colleagues, a group of healthy adults performed an emotion-generating task in the scanner and completed the LEAS 
. Covariate analysis revealed a significant cluster of activity in the dorsal ACC (Brodmann's area 24) that was positively correlated with LEAS scores. A more recent PET study replicated these results, and further demonstrated that the correlation between emotional awareness and dorsal ACC activity was specific to highly arousing pictures, and was stronger in women than men 
. Other functional magnetic resonance imaging (fMRI) and PET studies reported that alexithymic individuals had decreased activation of the dorsal ACC in response to painful pictures 
and emotional movie clips 
. In the “blindfeel” theory, Lane proposed clearly that the ACC might be the core neuroanatomical structure involved in alexithymia 
. Together with the evidence indicating the role of the ACC in voluntary control, it is likely that a person with more profound alexithymic trait would also possess poorer capacity of voluntary control, because of the common cause of a less efficient ACC function.
To date, few studies have directly tapped the relationship between alexithymic trait and voluntary control in general, especially in healthy adults, although a few domains of cognitive functions have been studied in association with alexithymia in patients. This line of research is important in that a significant correlation between measurement of voluntary control and that of alexithymia could verify that the two constructs are behaviorally relevant; and that a nonclinical sample would better elucidate the nature of alexithymia as a personality trait and/or an endophenotype and exclude the confounding factors introduced by other neurological and psychiatric conditions in patient studies. More specifically, it remains unclear (1) whether this impairment is specific to emotional processing, or is also related to a deficit in general cognitive processing, or a result of interaction of both cognitive control and emotional processing, and (2) which aspects of voluntary control might be related to alexithymic trait.
We used the TAS-20 to measure alexithymic trait in a group of healthy adult participants. Additionally, we measured participants' performance on the revised Attention Network Test (ANT-R) (state voluntary control), and individual differences in effortful control using the Adult Temperament Questionnaire (ATQ) (trait voluntary control). The ANT-R is a relatively challenging version that measures the general efficiency of voluntary control of attention, and the three networks subserving attention (alerting, orienting, and executive control). Correlation and regression analyses were performed on TAS-20 scores and participants' performance on ANT-R, and ATQ scores, to examine the association between alexithymic trait and voluntary control, and other aspects of temperament. We hypothesized that high alexithymia is correlated with (1) lower efficiency of state voluntary control indicated by slower response speed on the ANT-R task, and greater conflict effect; and (2) a deficiency in trait voluntary control, indexed by low scores on ATQ subscale Effortful Control.