Learning to trust our senses

To effectively interact with the environment we must estimate the reliability or precision of what we can perceive. For example, if we are looking for our dog in the park on a dark night, we may have low confidence in the precision of visual signals and therefore rely on other senses (e.g., hearing) or deploy other strategies to gain more information. This online assessment of confidence in our senses depends on metacognitive monitoring mechanisms in the brain which are thought to be influenced by contextual information (Deroy, Spence, & Noppeney, 2016; Pereira et al., 2020). While many scientists assume we do generate these kinds of 'beliefs about precision', it remains unclear whether this is the case and how confidence in our senses is encoded in the brain.

Ageing adults tend to make poorer decisions based on sensory signals and preliminary evidence suggests that perceptual metacognition also declines with age This raises the possibility that poor decision-making could be explained by our inaccurate beliefs about the precision of our senses. Establishing the fundamental cognitive and neural mechanisms of perceptual metacognition holds promise for understanding suboptimal beliefs and behaviour, especially those seen in older adults.

This PhD project will use a multi-method approach to characterise the cognitive
and neural mechanisms that underpin meta-level beliefs about the reliability of our senses and will investigate how these mechanisms change as we age.
Firstly, we will test the hypothesis that observers form meta-level beliefs about perception, and that these beliefs bias perceptual confidence. By using a classic motion coherence task (Britten, Shadlen, Newsome, & Movhson, 1992) and state-of-the art psychophysical measures of perceptual and metacognitive performance (Maniscalco & Lau, 2012), we will test whether expectations about signal strength bias perceptual confidence (e.g., are observers biased to be more confident in their choices when they expect strong signals?). We will then test whether such biases in confidence translate to strategic changes in behaviour e.g., if participants are not confident in their decision will they seek more information to improve their choice?

After investigating these fundamental mechanisms, we will use electroencephalography (EEG) to record electrical brain activity, applying state-of-the-art multivariate pattern decoding techniques to establish how signal strength is encoded in the brain and how these representations are shaped by metacognitive beliefs about signal strength. Participants will complete the same task while brain activity is recorded. First, analyses will establish whether objective signal strength is encoded in primary visual areas or 'higher' brain regions implicated in decision confidence. Once these regions are identified, we will ask whether pattern strength is altered by top-down expectations and will use the excellent temporal resolution of EEG to ask whether predictive biases emerge even before stimuli are presented. Transcranial magnetic stimulation (TMS) experiments will then use non-invasive brain stimulation to test the causal contribution of these brain areas in the effects found in the preceding experiments.

Finally, we will build on the mechanistic framework developed in these studies to explore how meta-level beliefs change across the lifespan by sampling a wide range of ages. This will identify any changes in these mechanisms that occur in healthy ageing, developing our understanding of how we monitor and rely on our senses as we age and how beliefs about the senses may go awry. Understanding these age-linked changes in perceptual metacognition and self-awareness is important for psychologists and has significant implications for the wider social sciences and public policy.