Clinical translational validity of sign-tracking phenotype in daily life: an ecological study

Background: The “Sign-tracker/Goal-tracker (ST/GT)” is an animal model describing individual differences in cue-reward learning. Sign-tracker rodents seem to be more at risk of developing addiction-like behaviours; however, despite the potential clinical relevance of this model, its translational validity has hardly been supported. The aim of the present study was to observe whether psychological traits co-segregating with STs in preclinical studies (i.e. impulsivity, obsessive-compulsive tendencies, alcohol abuse, internet addiction) would be associated with attribution of high incentive salience to ecological reward-related cues. Methods: We combined an ecological momentary assessment with ambulatory autonomic monitoring. 92 non-psychiatric participants filled out dispositional questionnaires evaluating traits that co-segregate with ST, and for two days they were frequently asked to rate the attractiveness of several preselected ecological rewards (e.g. coffee) and preceding cues (the smell of coffee) while their EKG was recorded. Random effect regression models were used as methods of analysis, and type of event (i.e. sign versus reward) was related to: self-rated level of attractiveness, heart- rate (HR) and its variability (HRV), and sympathovagal balance (LF/HF). Each model was repeated entering scores on BIS, OCI-R, IAT and AUDIT (treated as continuous variables) and the moderator × Type of event interaction term as predictors. Results: Type of event was neither a significant predictor of momentary self-reported attractiveness nor of physiological variables (ps < .0001). However, significant effects emerged when the assessed psychological traits were considered as moderators and the levels of momentary attractiveness as outcome. High levels of impulsivity predicted higher attractiveness toward the sign (4.49 (1.75)) compared to the reward (4.10 (1.59), d = 0.23), whereas low levels of impulsivity predicted higher attractiveness towards the reward (4.56 (1.62)) compared to the sign (4.05 (1.56), d = 0.32). Similarly, high levels of obsessive-compulsive tendencies predicted higher attractiveness toward the sign compared to reward (4.52 (1.72) vs 4.15 (1.62), d=0.22), while low levels of this trait predicted higher attractiveness toward the reward rather than the sign (4.38 (1.60) vs 4.26 (1.49), d=0.08). High levels of internet addiction and alcohol use predicted higher attractiveness toward the sign rather than the reward (4.50 (1.61) vs 4.18 (1.60), d=0.19; and 4.37 (1.67)) vs 4.15 (1.48), d=0.14, respectively); however, no significant differences were observed for low levels of these traits. When LF/HF was considered as outcome, high impulsivity, obsessive- compulsive tendencies, internet addiction and alcohol use predicted higher LF/HF to the sign compared to the reward (ps < .0001; impulsivity 1.14 (1.04) vs 0.89 (1.01), d= 0.24; obsessive- compulsive tendencies 1.31 (1.03) vs 1.22 (1.03), d= 0.12; internet addiction 1.29 (1.02) versus 1.00 (1.10), d = 0.27; alcohol use 1.29 (1.02) vs 1.09 (1.06); d = 0.19). No effects emerged for HR and HRV. Conclusions: Individuals with high levels of traits that co-segregate with ST rated as more attractive- and showed a greater increase in sympathetic arousal to- cues versus reward, whereas those with low levels of these dispositional traits showed opposite tendencies. This study represents an attempt to early detect individuals who are vulnerable to develop impulse-related disorders.