We investigated whether engaging in a music listening task varying in task demand produced a net reduction in physiological measures of central and peripheral arousal. Our conceptual development led to an operational definition of net engagement as a slope coefficient in the regression of the response on music task demand. We tested whether the magnitudes of these slope coefficients (net engagement proxies) varied as a function of absorption and anxiety, controlled for stimulus level and trial habituation/sensitization effects. Statistical evaluation of this question depends on testing and scaling the three-way interaction among task, absorption, and anxiety to address the question: Do personal characteristics interact with task demand to alter the engagement response? Although many studies treat high-order interactions as nuisances, this becomes a scientific question central to the present study and thus cannot be simplified.
We found that central arousal reliably decreased with increasing task demand. The SEP slopes varied with stimulus intensity with the largest reduction in SEP over task level occurring at the highest stimulus intensity. Indicators of peripheral arousal, PDR and SCR, suggested a more complex story understood only by considering personality factors. The three-way interactions with anxiety and absorption for PDR and SCR revealed very different engagement responses depending upon individual personality characteristics. We predicted that low anxiety/high absorbers would show the largest arousal decreases with increasing task demand, reasoning that high absorption would allow more task engagement and low anxiety would predict little interference from anxious thoughts and feelings. In fact this group showed the opposite effect: high anxiety/low absorbers had the lowest net engagement. Rather, high anxiety/high absorbers showed the greatest net engagement. These findings imply that arousal from anxiety may improve engagement, rather than interfering as predicted, especially for persons with high absorption. In fact, low anxiety appears to diminish the ability to engage, even for high absorbers.
Although these interactions present a complex pattern of relationships, we believe that the consistency in slopes for the combination of anxiety/absorption found for both PDR and SCR argues for a fairly simple and parsimonious explanation when understood as describing the combination of stimulus-related arousal and task-related arousal resulting in an indication of net engagement. That is, stimulus-evoked arousal decreases with increasing task-evoked arousal if engagement is effective but increases with task if the task fails to engage.
What can we conclude from these results about the effects of engagement on pain? Since we elected not to collect pain ratings in order to avoid interfering with engagement effects, we did not have subjective pain report as an indicator. Our results indicate that task performance reduced SEP and that these effects were consistent across individuals. Some literature suggests that SEP can provide a reliable surrogate for reported pain 37
, or perhaps only the affective but not sensory aspects of pain.45
However, this interpretation remains controversial.10
Donaldson et al. have identified a higher-order coordinated pattern of physiological responses that characterize a pain defense response and argue that a failure to form this higher-order pattern corresponds to reduced pain.13
The finding that PDR and SCR response patterns differed substantially from that for SEP suggest that the conditions for forming a pain defense response did not arise during the music listening task
The increased peripheral arousal with task level found for some subjects might indicate correspondingly greater experienced pain. However, whereas physiological arousal corresponds to emotional intensity, emotion labeling depends upon the object to which it is attributed.23
Thus, if subjects associated increased arousal to effort on task rather than to stimulations, they would not necessarily experience increased pain, even in high anxiety/low absorption subjects having the largest task-related arousal increases. Anecdotally, when interviewed after completing the test session, most subjects reported less pain during task performance.
Current thinking about anxiety differentiates anxious arousal (AR) (threat-evoked hyper-arousal and somatic tension) and anxious apprehension (AA) (threat-induced ruminative thoughts).31
In this view, AR high anxiety participants might show greater emotional arousal evidenced by higher SCR, whereas AA participants might display greater cognitive arousal and higher PDR. The STAI-Trait measure typically performs better identifying AA.31
This suggests that high anxiety/low absorbers’ ruminative thoughts about threat would interfere with their ability to engage in the task whereas high anxiety/high absorbers might engage well, even benefiting by having a task on which to direct their thoughts. High anxiety participants may have experienced task anxiety as well and this may have been the source of anxiety reflected in their arousal measures. For high absorbers, performance anxiety may actually enable more effective engagement.
Anxiety, particularly when coupled with pain catastrophizing, may interfere with pain distraction techniques rendering them ineffective.4, 7, 40
Studies have shown that catastrophizing contributes to failure to disengage attention from pain cues.34, 39
Brain imaging research confirms these findings, showing that anxiety biases attentional networks (e.g., amygdala-prefrontal circuits) towards activation of threat-related representations and contributes to under-activation of alternative non-threat-related representations.2
However, emerging work suggests an initial anxiety-provoked attentional bias may be followed by a defensive response that activates attentional orientation towards positive events that present a defense mechanism reducing negative anxiety-associated mood states. This defensive response mechanism seems particularly robust in high anxiety individuals.29
Our results indicate that ability to absorb in a task may improve one’s chances for reducing pain by engagement, even, or especially, if one has a strong tendency for anxious rumination. This conclusion is further supported by work showing that anxiety can have pain-reducing effects, particularly if attention is directed toward an anxiety provoking (but non-painful) object.17
Several studies have investigated effects of task performance on pain and effects of pain on task performance in the same experiment. These studies consistently show that pain interferes with task performance, particularly if the threat value of pain is high.12, 14
These findings may explain the low engagement found with high anxiety/low absorbers, suggesting that anxiety interfered with task engagement more readily due to low capacity for absorption.
For this study we selected a music listening task because it provided several characteristics essential for effective engagement for pain reduction: 1) acoustic properties of music activate sensory pathways that compete with nociceptive pathways; 2) music listening, especially when done actively, requiring complex cognitive/attentional processes; 3) motor assembly processes to deliver speeded responses; and 4) affective/motivational processes associated with performance expectations and properties of the music that may innately and automatically activate emotional associations.20
Finally, this activity could be maintained over an extended time period (most test sessions lasted 30 minutes or more) with consistent performance. According to constructivist theory, an activity that is sufficiently engaging to compete with pain must be contextually rich, dynamic, and complex enough to be engaging intellectually and meaningful enough to be engaging emotionally and motivationally. Music listening meets these requirements for most people.21
Music has been widely used for pain relief but a review of its efficacy found only small benefit.8
Music’s effects have been attributed to distraction30
or its ability to evoke emotion.33
Most studies fail to appreciate the important contributions of preference,30
and emotional connection.27
The relevance of a goal and the motivation for pursuing it may play a significant role in the capacity of a task to modulate pain.24, 41
The importance of motivation has been demonstrated for behavioral pain relief interventions.42
Music listening can be intrinsically motivating, and when combined with a task and monitored performance, particularly compelling.
Limitations, Implications, and Future Research
This study lacked a no-stimulus task condition providing task performance baseline arousal measures that could then be compared with arousal during stimulus-no task and stimulus-task conditions. The study as designed allowed only extrapolations from responses to noxious stimulation under different task conditions to impute changes in arousal to stimulation or task conditions but not direct measures of each. Noxious stimulation produced phasic physiological changes that were easily detected in this study; responses to musical events prove more difficult to detect. In preliminary work, our attempts to identify responses to musical events failed largely because signal changes were small and easily swamped by the larger responses to noxious stimuli. Future studies must synchronize events carefully to assure ability to detect and separate responses from different modalities. Analytical methods that can disambiguate convolved signals may prove effective for this purpose.1
Finally, corroborating these results with subjective pain report that only minimally interferes with engagement is warranted.
We limited the auditory stimuli used for the listening task to simple melodies to assure that subjects knew them well, could easily generate and track memory representations to detect errors. Although background tones provided a context for manipulating task difficulty, the result admittedly did not provide a pleasing listening environment. A listening activity that provides a more pleasant emotional experience might provide more effective engagement.
The question of music engagement’s ability to relieve pain has no simple answer. In this study, trait anxiety and ability to absorb in a task contributed significantly to how well music engagement reduced stimulus arousal. Our results suggest that engaging activities like music listening may be most effective for reducing pain in high anxiety persons who can easily become absorbed in activities. These findings build on results from studies showing anxiety, fear of pain, catastrophizing, and motivation influence effectiveness of behavioral interventions for pain relief. The interaction of anxiety and absorption is a new finding and suggests that these personality characteristics should be considered when recommending engagement for pain relief. Since this study did not assess fear of pain or catastrophizing in participants this limitation precludes drawing any conclusions regarding potential influences of these personality characteristics on the potential effectiveness of engagement.
Engaging in music listening can reduce responses to pain, depending on the person: people who are anxious and can become absorbed in activities easily may find music listening especially effective for relieving pain. Clinicians should consider patients’ personality characteristics when recommending behavioral interventions like music listening for pain relief.