Melbourne School of Psychological Sciences - Research Publications
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ItemFeedback discounting in probabilistic categorization: Converging evidence from EEG and cognitive modelling(Springer International Publishing, 2018)In simple probabilistic learning environments, the informational value of corrective feedback gradually declines over time. This is because prediction errors persist despite learners acquiring the contingencies between stimuli and outcomes. An adaptive solution to the problem of unavoidable prediction error is to discount feedback from the learning environment. We provide novel neural evidence of feedback discounting using a combination of behavioral modeling and electroencephalography (EEG). Participants completed a probabilistic categorization task while EEG activity was recorded. We used a model-based analysis of choice behavior to identify individuals that did and did not discount feedback. We then contrasted changes in the feedback-related negativity (FRN) for these two groups. For individuals who did not discount feedback, we observed learning-related reductions in the FRN that reflected incremental changes in choice behavior. By contrast, for individuals who discounted feedback, we found that the FRN was effectively eliminated due to the rapid onset of feedback discounting. The use of a feedback discounting strategy was linked to superior performance on the task, highlighting the adaptive nature of discounting when trial-to-trial outcomes are variable, but the long-term contingencies relating cues and outcomes are stable.
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ItemHealth warnings promote healthier dietary decision making: Effects of positive versus negative message framing and graphic versus text-based warnings(Elsevier, 2018-08-01)Food product health warnings have been proposed as a potential obesity prevention strategy. This study examined the effects of text-only and text-and-graphic, negatively and positively framed health warnings on dietary choice behavior. In a 2 × 5 mixed experimental design, 96 participants completed a dietary self-control task. After providing health and taste ratings of snack foods, participants completed a baseline measure of dietary self-control, operationalized as participants' frequency of choosing healthy but not tasty items and rejecting unhealthy yet tasty items to consume at the end of the experiment. Participants were then randomly assigned to one of five health warning groups and presented with 10 health warnings of a given form: text-based, negative framing; graphic, negative framing; text, positive framing; graphic, positive framing; or a no warning control. Participants then completed a second dietary decision making session to determine whether health warnings influenced dietary self-control. Linear mixed effects modeling revealed a significant interaction between health warning group and decision stage (pre- and post-health warning presentation) on dietary self-control. Negatively framed graphic health warnings promoted greater dietary self-control than other health warnings. Negatively framed text health warnings and positively framed graphic health warnings promoted greater dietary self-control than positively framed text health warnings and control images, which did not increase dietary self-control. Overall, HWs primed healthier dietary decision making behavior, with negatively framed graphic HWs being most effective. Health warnings have potential to become an important element of obesity prevention.
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ItemEvaluating the influence of message framing and graphic imagery on perceptions of food product health warnings(ELSEVIER SCI LTD, 2019-10)Food product health warnings may be a valuable intervention strategy for helping reduce obesity rates and the negative health outcomes associated with consuming an unhealthy diet. Research into the efficacy of food product health warnings has shown promising effects on consumers’ beliefs and behaviour, but existing research has typically featured a single or limited number of simple, text-only warnings. Two studies are presented that tested the influence of text-only and text-and-graphic, positively and negatively framed health warnings on perceived efficacy, negative affect and motivation to change behaviour. Using a between-subjects design, Study 1 found that negatively framed health warnings and text-and-graphic health warnings produced more negative emotional responses than positively framed and text-only health warnings. Study 2 then featured the highest rated message topics from Study 1. Using a within-subjects design, Study 2 found that participants rated text-and-graphic health warnings as more effective than text-only warnings, and negatively framed warnings as more effective than positively framed warnings, though all warning groups scored above the scale mid-point on perceived efficacy. Negatively framed warnings produced stronger negative emotional responses, while positively framed warnings produced stronger feelings of motivation to change behaviour. Results indicate that food product health warnings were perceived as capable of effectively promoting behavioural change. While negatively framed warnings were seen as most effective, positively framed warnings may also be effective, possibly through a different persuasive pathway.
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ItemFood product health warnings promote dietary self-control through reductions in neural signals indexing food cue reactivity(Elsevier, 2018)Modern societies are replete with palatable food cues. A growing body of evidence suggests that food cue exposure activates conditioned appetitive physiological and psychological responses that may override current metabolic needs and existing eating goals, such as the desire to maintain a healthy diet. This conditioned response results in unhealthy dietary choices and is a contributing factor in the current obesity epidemic. Prime based obesity prevention measures such as health warnings at point-of-sale or on product packaging may have the potential to counteract the influence of the obesogenic environment at the crucial moment when people make food purchasing or consumption decisions. Existing research into the efficacy of these intervention strategies has predominantly employed self-report and population level measures, and little evidence exists to support the contention that these measures counteract food cue reactivity at the time of decision making. Using a dietary self-control priming paradigm, we demonstrated that brief exposure to food product health warnings enhanced dietary self-control. Further, we analysed electroencephalographic correlates of selective attention and food cue evoked craving (N1, P3, LPP) to show that health warning exposure reduced the automatic appetitive response towards palatable food cues. These findings contribute to existing evidence that exogenous information can successfully prime latent goals, and substantiate the notion that food product health warnings may provide a new avenue through which to curb excessive energy intake and reduce rising obesity rates.