Hypothetical decision making in schizophrenia: the role of expected value computation and "irrational" biases

Abstract

The aim of the present study was to examine the contributions to decision making (DM) deficits in schizophrenia (SZ) patients of expected value (EV) estimation and loss aversion. Patients diagnosed with SZ (n=46) and healthy controls (n=34) completed two gambling tasks. In one task, participants chose between two options with the same EV across two conditions: Loss frames and Keep frames. A second task involved accepting or rejecting gambles, in which gain and loss amounts varied, determining the EV of each trial. SZ patients showed a reduced "framing effect" relative to controls, as they did not show an increased tendency to gamble when faced with a certain loss. SZ patients also showed a reduced tendency to modify behavior as a function of EV. The degree to which choices tracked EV correlated significantly with several cognitive measures in both patients and controls. SZ patients show distinct deviations from normal behavior under risk when their decisions are based on prospective outcomes. These deviations are two-fold: cognitive deficits prevent value-based DM in more-impaired patients, and in less-impaired patients there is a lack of influence from well-established subjective biases found in healthy people. These abnormalities likely affect everyday DM strategies in schizophrenia patients.

Keywords: Framing effects; Loss aversion; Prospect theory; Risk.

Fig. 1

Illustration of behavioral tasks. (A) A trial involving a Keep frame from the DeMartino Framing Task (2006). In this example, participants started with $50 and had to decide whether they would rather keep $40 certainly, or accept a gamble with an 80% of keeping the entire $50 and a 20% chance of keeping nothing. (B) A trial involving a loss frame from the DeMartino Framing Task (2006). In this example, participants started with $75 and had to decide whether they would rather lose $60 certainly, or accept a gamble with an 80% of losing the entire $75 and a 20% chance of losing nothing. (C) Illustration of a “Catch” trial from the DeMartino Framing Task (2006). In this example, participants started with $100 and had to decide whether they would rather lose $50 certainly, or accept a gamble with a 5% chance of losing the entire $100 and a 95% chance of losing nothing. (D) Trial with an advantageous gamble from Tom et al. (2007). The gamble option from this trial had a very positive EV (17.5), due to large potential gain and small potential loss. (E) Trial from Tom et al. (2007) with a disadvantageous gamble (EV=−5), due to large potential loss and small potential gain.

Fig. 2

Results from DeMartino Task. When we examined gambling performance on the DeMartino task in the 34 patients and 31 controls who showed valid Catch trial performance, we observed a significant group difference in the direct measure of the framing effect (the [percentage gamble in Loss frames–percentage gamble in Keep frames] contrast.

Fig. 3

Results from Tom Loss-aversion Task. (A) Heat maps showing gradients of gamble acceptance, according to trial gain and loss magnitude, in controls and (B) patients, as well as (C) the contrast [controls–patients]. (D) Plots showing proportions of gambles accepted by loss magnitude, collapsed across all levels of gain magnitude. (E) Plots showing proportions of gambles accepted by gain-magnitude, collapsed across all levels of loss magnitude. (F) Measures of loss-aversion (λ) in patients and controls with valid β-values for gain and loss magnitude.