Concreteness and emotional valence of episodic future thinking (EFT) independently affect the dynamics of intertemporal decisions

Abstract

During intertemporal decisions, the value of future rewards decreases as a function of the delay of its receipt (temporal discounting, TD). Since high discount rates have been associated with a series of problematic behaviours and clinical conditions, current research has focused on possible modulators of TD. Specifically, a reduction of individual discount rates has been shown during episodic future thinking (EFT), wherein time intervals are anchored to personal future events. However, it is not entirely clear whether this effect is mediated by a change in the representation of future events (i.e., from abstract to concrete) or by a positive-emotion modulation. Here, we investigated this issue by manipulating the valence of the EFT (i.e., using negative, neutral and positive episodic tags), and by collecting explicit and implicit measures of behaviour. The results showed a significant reduction of TD in all the three emotional conditions compared to the baseline, with differences among them, thus suggesting the existence of a cumulative effect of the concreteness and affective components of the EFT. The analyses of implicit measures additionally revealed that this effect was mediated by a simultaneous increase/decrease of attraction toward the delayed/immediate alternative. Finally, these effects appeared to be modulated by participants' baseline discounting preferences. These findings provide important insights on clinical applications in reward-related disorders.

Fig 1. Behavioural paradigm.

(A) Baseline session: to ensure a proper recording of the mouse position at the beginning of each trial participants were instructed to press the “START” button positioned at the central bottom of the screen to visualize the choice options. Participants were subsequently instructed to express their preference by clicking on the corresponding response button. (B) Episodic future thinking session (EFT): as in the baseline session participants were firstly instructed to press the “START” button to visualize the choice options. In this session, however, along with the amount and delay time, an additional subject-specific episodic cue was displayed. The session was divided into three experimental blocks–with negative, neutral and positive emotional valences cues—presented in a counterbalanced order across participants.

Fig 2. Effects of EFT manipulation on explicit measures.

(A) Hyperbolic functions estimated across the four experimental conditions. (B) Results of the linear mixed-effects model conducted on discount rates (k) using the fixed effect of condition. (C) Results of the linear mixed-effects model conducted on subjective values using the fixed effect of condition, time delay and their interaction term.

Fig 3. Effects of EFT manipulation on implicit measures.

(A) Mean mouse trajectories across response type (now, later) and condition (baseline, negative, neutral and positive). (B, C) Results of the mixed-effects models conducted to predict maximum deviation (B) and area under the curve (C) using the fixed effects of the condition (baseline, negative, neutral and positive), response type (now, later) and the interaction term between them.

Fig 4. Influence of baseline preferences on explicit change measure (k-shift).

Results of the linear mixed-effects models conducted to predict the magnitude of the EFT effect (k shift) using the fixed effect of the emotional valence (negative, neutral and positive), the group (discounter, farsighted) and the interaction term.

Fig 5. Influence of baseline preferences on the implicit measures (spatial indices of mouse kinematics).

(A) Mean mouse trajectories associated with now/later responses in the two groups of discounters and farsighted participants and across the four experimental conditions. (B-C) Results of the linear mixed effect models conducted to predict the maximum deviation (B) and the area under the curve (C) using the fixed effects of the condition (baseline, negative, neutral and positive), response type (now, later), group (discounters, farsighted) and the second and third level interactions between them.