The main goal of this research project was to provide novel insights on the cognitive and neural mechanisms via which humans violate the principles of rationality when making simple decisions. Rational theories of choice prescribe that the subjective value ascribed to an...
The main goal of this research project was to provide novel insights on the cognitive and neural mechanisms via which humans violate the principles of rationality when making simple decisions. Rational theories of choice prescribe that the subjective value ascribed to an alternative is solely a function of the goals of the decision-maker and the objective properties of the alternative at hand. However, it has been shown time and again that the subjective value of an alternative is also largely influenced by the properties of the other alternatives that are under offer (i.e. context-sensitive valuation). Yet, very little is known about the mechanistic and neural basis of context-sensitive valuation in humans.
Understanding why humans make irrational decisions can lead to an enriched mechanistic theory of choice, revising thus the descriptively inadequate standard microeconomic model that has dominated the social sciences for decades. Additionally, a mechanistic theory of choice can generate novel predictions about choice behaviour in the healthy brain as well as in neuropsychiatric diseases. Being able to link specific neuropsychiatric disturbances (e.g. at the level of neurotransmitters) to concrete behavioural signatures can have clinically diagnostic value.
In this project, we used a simple psychophysical task in which participants view 2 rapid streams of numerical values and at the end of the trial have to decide which stream had the highest average value. In previous work, the researcher has shown that decisions in this simple task are subject to irrational context-sensitivities. These context-sensitivities have been previously ascribed to an attentional selection mechanism, which prioritises the processing of momentarily higher values. This project aimed to extend these findings via the following objectives:
a) Identify the cortical dynamics of attentional selection (that mediates irrational context-sensitivities) using magnetoencephalography (MEG).
b) Alter the cortical mechanisms of attentional selection by pharmacologically increasing GABA-mediated cortical inhibition.
c) Synthesize the findings in a) and b) into a novel biophysical model of attention and decision-making.
In a double-blind (placebo, drug) MEG study, we recorded MEG and eye-tracking data from 40 individuals whilst they performed our simple choice task. Subsequently, the MEG data were pre-processed and projected onto source space. The MEG data were analyzed in two different ways:
1) As continuous signal, using detrended fluctuation analysis in order to derive the excitation-inhibition ratio for each individual. This analysis exploited MEG data during task performance as well as during periods of rest, in which participants maintained fixation at a point on the screen.
2) By performing time-frequency analyses focused on each behavioural trial and the assorted events occurring therein.
Overall, we found that attentional selection, mediated by GABA-ergic inhibition, directly affects the context-sensitivity of human decision-making. This conclusion was supported by i) linking the excitation-inhibition balance (extracted by applying detrended fluctuation analyses on the continuous MEG signal) to behavioural signatures of decision irrationality, ii) observing that the pharmacological enhancement of GABA increases decision irrationality tendencies in healthy individuals. We made sense of these findings by building computational models that explained information processing in our simple choice task (at the algorithmic and biophysical levels). These models have been used to generate predictions about choice behaviour in schizophrenic patients, with disturbed excitation-inhibition profiles.
Results were disseminated in international conferences, workshops and symposia as well as peer-reviewed articles:
Poster presentations at SFN 2017 and FENS 2018.
Oral presentations in the Mathematical Psychology annual meeting (2017; 2 presentations) and in the conference of the Cognitive Science Society (2017).
6 invited presentations in the following institutions: CIMeC- University of Trento; Reading Emotions Symposium- University of Reading; Behavioural Science Group- University of Warwick; Department of Psychology- University of Edinburgh; Paris School of Economics- University of Pantheon-Sorbonne; Department of Cognitive Studies- Ecole Normale SupÃ©rieure, Paris.
Papers in Psychological Review, Psychological Science, Behavioral and Brain Sciences and Current Biology. The main MEG and modeling results are currently being prepared for publication.
The project website (on researcher\'s personal webpage) as well as relevant code and data will become available upon publication of a preprint pertinent to the main MEG and modeling results.
In this project we, for the first time, pinpointed empirical violations of rational choice theories onto the specifics of neural information processing at the level of cortical dynamics and the function of neurotransmitters.
This research is thus paving the wave for the development of a novel descriptively enhanced and neurally-constrained theory of decision-making, going beyond the mainstay approaches in the field of decision-making.
Additionally, beyond basic-science impact, the mechanistic understanding of human decision-making that we obtained in the duration of this project has helped us initiate new collaborations with psychiatrists. These collaborations are currently at an advanced stage and their aim is to established a link between perturbed excitation-inhibition balance in schizophrenia and behavioural performance in our task. Establishing this link will lead to the development of novel diagnostic tools, which is expected to have extended soietal implications and impact.