The date/delay effect in intertemporal choice: A combined fMRI and eye‐tracking study

Human Brain Mapping · 6 authors, 5 centres

AI SUMMARY

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POPULATION31 healthy right-handed adults (15 male, 16 female; mean age 23.26 years, SD 3.19) from a student population

INTERVENTIONIntertemporal choice task with time framed as dates (date condition)

COMPARISONIntertemporal choice task with time framed as delay units (delay condition)

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TL;DR

This study combined fMRI and eye-tracking to investigate the neural and cognitive mechanisms of the date/delay effect, where framing time as dates (e.g., June 8, 2023) reduces temporal discounting compared to delays (e.g., 30 days). The date condition led to lower discount rates, longer reaction times, increased fixations on time attributes, and greater activation in episodic memory regions (precuneus, angular gyrus) and prefrontal areas, supporting the differential time estimation and choice strategy hypotheses. These findings suggest that dates promote more episodic processing and a less arithmetic, more heuristic decision strategy, which may inform interventions to reduce impulsive choice.

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**Background:** The date/delay effect refers to the phenomenon that people discount future rewards less when time until receipt is framed as dates (e.g., June 8, 2023) compared to delay units (e.g., 30 days). While this effect is well replicated, its cognitive and neural mechanisms remain unclear. Proposed mechanisms include differential time estimation (dates appear subjectively shorter), attention-focusing/reward-weighting (dates draw attention to rewards), and choice strategy changes (dates impede calculation, prompting attribute-based comparisons). This study combined fMRI and eye-tracking for the first time to investigate these mechanisms.

**Methods:** Thirty-two healthy participants (final N=31 after exclusion for head movement) completed a Monetary Choice Questionnaire (27 items) in both date and delay conditions during fMRI. Eye movements were recorded with an MR-compatible eye tracker. Discount rates were estimated using hierarchical Bayesian modeling with a hyperbolic function. Eye-tracking measures included saccade frequencies and fixation durations within and between areas of interest (AOIs). fMRI data were analyzed using a general linear model with parametric modulation by subjective value (SV). Whole-brain and region-of-interest (ROI) analyses were performed.

**Key Results:** The date/delay effect was replicated: log-transformed discount rates were lower in the date condition (M=-5.72, SD=1.17) than the delay condition (M=-5.27, SD=1.55), t(30)=-3.96, p<.001, g_av=0.33. Reaction times were longer in the date condition (M=2.59 s, SD=0.66) vs. delay (M=2.26 s, SD=0.55), t(30)=7.22, p<.001, g_av=0.54. Eye-tracking (N=18 after exclusions) showed more saccades within AOIs in the date condition (M=3.48, SD=1.38) vs. delay (M=2.45, SD=1.01), t(17)=6.87, p<.001, g_av=0.84. The Payne index (proportion of vertical vs. horizontal saccades) was lower in the date condition, t(17)=-3.09, p=.007, g_av=0.41, driven by more horizontal saccades between time attributes, t(17)=7.73, p_adj<.001, g_av=1.20. Fixation durations on time attributes were longer in the date condition, t(16)=8.75, p_adj<.001, g_av=1.59, while reward fixations were shorter, t(16)=-2.58, p_adj=.020, g_av=0.36. fMRI revealed greater activation in the date > delay contrast in visual areas, left posterior cingulate cortex (PCC), right precuneus, left middle/superior frontal gyrus (MFG/SFG), and bilateral angular gyrus. ROI analysis showed a significant SV signal in the ventral striatum (vS) in the delay condition (t(30)=2.60, p=.014, d=0.47) but not in the date condition (t(30)=-0.42, p=.674, d=0.08), with a significant difference between conditions (t(30)=2.18, p=.037, g_av=0.57). No significant SV signal was found in vmPFC. Covariate analysis showed that a lower behavioural date/delay effect correlated with higher activity differences in bilateral occipital areas, cerebellum, right SFG, bilateral MFG, bilateral posterior medial frontal cortex (pMFC), and left ACC/MCC in the date > delay contrast.

**Clinical Implications:** The date/delay effect offers a simple, non-invasive way to reduce temporal discounting, which is associated with negative life outcomes (e.g., debt, risky behavior) and mental disorders. By framing time as dates, individuals may engage more episodic thinking and less arithmetic calculation, leading to more patient choices. This could inform interventions in clinical populations (e.g., substance use disorder, ADHD) where steep discounting is common. However, the effect varies between individuals, and those who show a smaller effect may rely more on cognitive control and calculation. Future research should explore whether training or cueing episodic thinking can enhance the date/delay effect in clinical settings.

PICO

PPOPULATION

31 healthy right-handed adults (15 male, 16 female; mean age 23.26 years, SD 3.19) from a student population

IINTERVENTION

Intertemporal choice task with time framed as dates (date condition)

OOUTCOME

Temporal discounting rates (log-transformed k), reaction times, eye-tracking measures (saccade frequencies, fixation durations), BOLD fMRI activation, subjective value signals in ventral striatum and ventromedial prefrontal cortex

STUDY TYPE

other

SPECIALTY

ophthalmology

SUMMARISED BY

AI pipeline

FIDELITY CHECK

100% · A

ORIGINAL PAPER

PMC10893971

The date/delay effect in intertemporal choice: A combined fMRI and eye‐tracking study

Human Brain Mapping

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ABSTRACT

Abstract Temporal discounting, the tendency to devalue future rewards as a function of delay until receipt, is influenced by time framing. Specifically, discount rates are shallower when the time at which the reward is received is presented as a date (date condition; e.g., June 8, 2023) rather than in delay units (delay condition; e.g., 30 days), which is commonly referred to as the date/delay effect. However, the cognitive and neural mechanisms of this effect are not well understood. Here, we examined the date/delay effect by analysing combined fMRI and eye‐tracking data of N = 31 participants completing a temporal discounting task in both a delay and a date condition. The results confirmed the date/delay effect and revealed that the date condition led to higher fixation durations on time attributes and to higher activity in precuneus/PCC and angular gyrus, that is, areas previously associated with episodic thinking. Additionally, participants made more comparative eye movements in the date compared to the delay condition. A lower date/delay effect was associated with higher prefrontal activity in the date > delay contrast, suggesting that higher control or arithmetic operations may reduce the date/delay effect. Our findings are in line with hypotheses positing that the date condition is associated with differential time estimation and the use of more comparative as opposed to integrative choice strategies. Specifically, higher activity in memory‐related brain areas suggests that the date condition leads to higher perceived proximity of delayed rewards, while higher frontal activity (middle/superior frontal gyrus, posterior medial frontal cortex, cingulate) in participants with a lower date/delay effect suggests that the effect is particularly pronounced in participants avoiding complex arithmetic operations in the date condition. Keywords: date/delay effect, episodic thinking, eye‐tracking, fMRI, precuneus, temporal discounting

CITATION EXPORT

Kristof Keidel, Rebekka Schröder, Peter Trautner et al.. The date/delay effect in intertemporal choice: A combined fMRI and eye‐tracking study. Human Brain Mapping. (2024). https://doi.org/10.1002/hbm.26585

AUTHORS

6 · 5 CENTRES

Kristof Keidel, Rebekka Schröder, Peter Trautner, Alexander Radbruch, Carsten Murawski, Ulrich Ettinger

1 Department of Psychology, University of Bonn, Bonn, Germany
2 Department of Finance, Centre for Brain, Mind and Markets, The University of Melbourne, Carlton, Victoria, Australia
3 Core Facility Human 3T MRI, University of Bonn, Bonn, Germany
4 Clinic of Neuroradiology, University Hospital, Bonn, Germany
5 Clinical Neuroimaging, German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany