In the current study we compared cocaine addicted individuals and healthy controls on choice for viewing pictures of cocaine and standardized pleasant, unpleasant, and neutral pictures, exploring objective cocaine-related choice as a potential marker of addiction severity. We also tested whether choice for viewing cocaine pictures could be fully explained by self-reported ratings of pleasantness and arousal of these stimuli, exploring the novel hypothesis of compromised insight into behavior in drug addiction.
Consistent with our first a priori hypothesis, CUD chose cocaine pictures more than healthy controls. This finding demonstrates drug-related choice in cocaine addiction even for non-pharmacological (pictorial) stimuli, and is consistent with research showing that cocaine-related stimuli have attention-biasing properties in CUD (13
). Other contributing factors to this choice in CUD may have included enhanced interest, affinity, motivation, salience, or familiarity with these particular drug stimuli. Nevertheless, in the present study drug-related choice in CUD cannot be attributed to motor perseveration (in both tasks location of the cocaine pictures was pseudorandomly varied) or overall increased button pressing/selection (no group main effect emerged in either task, and results remained significant in subsequent ANCOVAs that controlled for total button press/selection).
Consistent with our second a priori hypothesis, this enhanced drug-related choice in the CUD was not completely explained by their self-reported ratings. Moreover, CUD’s self-reported ratings were incongruent with their choice behavior, as indicated by discrepancies between picture ratings (cocaine<pleasant) and objective choice as assessed in both tasks (cocaine=pleasant). Together, such results suggest a disconnect in drug addiction between self-reports (as measures of conscious awareness) and objective markers of behavior, as possibly indicative of impaired awareness of internal drives (11
) or of cognitive-behavioral performance (38
). Such impaired awareness may potentially underlie the evasive nature of using self-reported craving to predict relapse in drug addiction (40
), and highlights the potential utility of our choice tasks as objective markers of individualized clinical outcomes.
Finally, results of both tasks showed that cocaine-related choice in CUD surpassed unpleasant, but not pleasant, picture choice. These findings suggest that drug seeking in CUD (as approximated here with cocaine picture choice) may be higher in the presence of aversive stimuli, but not in the presence of alternative pleasant stimuli, consistent with both human and animal studies (41
). This interpretation is also consistent with the significant correlations in the current study between choice for viewing cocaine pictures, even when directly compared to selections of reportedly more pleasant pictures, and frequency of actual cocaine use. Therefore, behavior on this task may be an indirect marker of actual drug-choice behavior, as remains to be tested in future studies.
Limitations of this study include: (A) previous viewing and rating of the same cocaine pictures may have precipitated cue-induced craving in CUD (49
). Counterbalancing picture ratings and picture choice tasks should be implemented in future studies; (B) unexpectedly, healthy control subjects selected fewer cocaine than unpleasant pictures in the implicit task. A completely masked task would eliminate the possible confounding influence of socially desirable responding and other demand characteristics that may have partially driven this finding. Similarly, for CUD, the discrepancy between pleasantness ratings and task performance could have also reflected socially desirable self-reporting; (C) habituation could have resulted from viewing the same blank screen throughout. However, control subjects pressed for these blank screens over the unpleasant or cocaine pictures, suggesting habituation did not significantly impact our results and further highlights control subjects’ aversion to such pictures; (D) our CUD group was heterogeneous, as it included both active users and treatment-seekers. Larger CUD samples can ascertain whether study results differ as a function of active cocaine use (e.g., 50
In summary, two newly-developed tasks examined choice for viewing cocaine pictures in comparison to pleasant, unpleasant, and neutral pictures. CUD selected more, and worked more for, cocaine pictures than healthy control subjects, results that were not fully driven by (or subject to the pitfalls of) self-report. Results also revealed that drug picture choice did not differ from pleasant picture choice but was enhanced when compared to unpleasant picture choice, possibly indicative of modulation of actual drug choice by other pleasant or aversive stimuli in drug addicted individuals. Further studies are needed to uncover the neural substrates that underlie this drug-biased choice in CUD, and whether cue-reactive states enhance such choice over pleasant stimuli (1
), especially in individuals with more severe drug use. Overall, such disadvantageously enhanced drug choice could provide a marker of the neurocognitive dysfunction that characterizes drug addiction.