Does the Central Bottleneck Encompass Voluntary Selection of Hedonically Based Choices?

Pashler, Harold; Harris, Christine R.; Nuechterlein, Keith H. · 2008 · Experimental Psychology (formerly Zeitschrift für Experimentelle Psychologie)

DOI: 10.1027/1618-3169.55.5.313

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Summary

This study investigates whether the central processing bottleneck, a well-documented constraint in multitasking that prevents simultaneous decision-making, also applies to voluntary, hedonically based choices. Previous research on the psychological refractory period (PRP) effect primarily utilized tasks requiring the retrieval of pre-instructed responses. The authors questioned whether spontaneous decisions, made to optimize anticipated rewards or avoid losses, might bypass this bottleneck due to their affective nature or distinct neural underpinnings. To address this, the researchers designed an experiment combining a standard tone-response task with a gambling task involving real monetary stakes. The experimental design involved 30 participants performing two tasks in close succession. The first task required pressing a key corresponding to the pitch of a tone. The second task, modeled after the Iowa Gambling Task, required participants to accept or reject a card drawn from one of three decks (blue, green, or yellow), each with different probabilities of gain or loss and varying expected values. The stimulus-onset asynchrony (SOA) between the tone and the card varied from 100 ms to 1200 ms. Participants were incentivized to respond quickly and accurately, with real money at stake for the gambling decisions. The study measured response times (RTs) for both tasks to determine if factors influencing the gambling decision interacted additively or subadditively with SOA. The results demonstrated a classic PRP effect, where response times for the gambling task slowed significantly as the SOA decreased. Crucially, three factors affecting the gambling decision—deck color (expected value/risk), the choice itself (accept vs. reject), and sequential consistency (whether the current choice matched the previous outcome for that deck color)—all showed additive interactions with SOA. For instance, responses to blue cards (negative expected value) were slower than to yellow cards, and this difference remained constant across all SOA levels. Similarly, rejecting a card took longer than accepting one, and changing one’s mind relative to the previous trial added consistent latency. These additive effects indicate that the time required for the voluntary decision process is delayed by the first task, rather than occurring in parallel. The findings conclude that voluntary selection of hedonically based choices is subject to the same central bottleneck as the retrieval of pre-instructed responses. This suggests that the bottleneck encompasses the entire decision-making process, including the evaluation of outcomes and the formation of voluntary choices, not just the final motor selection. The study challenges the notion that affective or reward-based decisions operate independently of central cognitive constraints, implying that human multitasking limitations are more pervasive than previously thought, affecting even spontaneous, goal-directed behaviors.

Key finding

Voluntary selection of hedonically based choices is subject to the same central processing bottleneck as the retrieval of preinstructed responses in dual-task paradigms.

Methodology

lab_experiment

Sample size: 30

Provenance

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Topics

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• dual task multitasking