Use this URL to cite or link to this record in EThOS:
Title: Human sign-tracking : an investigation into its mechanisms, measurements and neuropsychological correlates
Author: Duckworth, J.
ISNI:       0000 0004 7428 4800
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2017
Availability of Full Text:
Access from EThOS:
Access from Institution:
Sign-tracking describes the behaviour of individuals who attribute incentive salience to irrelevant, reward-associated cues, whereas goal-tracking pertains to individuals who use such cues only as predictive tools for upcoming rewards. The importance of the signtracker/goal-tracker phenotypes has been noted in the preclinical literature, with researchers suggesting that they are useful for the study of addiction. This thesis provides translational data, examining sign-tracking and goal-tracking in human social drinkers across six separate experiments. Chapter One reviews the relevant literature on sign-tracking, covering the history of its discovery, its mechanisms, correlates, effects and aetiologies. Chapter Two details the general methods used across experiments (computer tasks and questionnaires). Chapter Three is the first experimental chapter; it presents the largest study of human sign-tracking to date, assessed via the additional singleton tracking task (ASTT). Results revealed a sign-tracking effect in a sample of social drinkers; however, no association to individual differences (e.g., weekly alcohol consumption, impulsivity etc.) was found. This study suggests that human sign-tracking is real, automatic, and driven by pavlovian conditioning. Chapter Four contains two alcohol priming experiments, the first testing a 0.3 g/kg dose, the second a 0.6 g/kg dose. The lower dose, but not higher, magnified sign-tracking compared to a control drink. Chapter Five used a novel variant of the ASTT which contained three (rather than the usual two) reward-associated distractor cues. Results revealed that signtracking pertained only to the high-value and medium-value cues, with the low-value cue seemingly being ignored. This study provides unique insight into how sign-tracking changes in more complex reward displays. Chapter Six attempted to compare three sign-tracking tasks: two variants of the ASTT and a Pavlovian-to-Instrumental Transfer (PIT) task. However, all tasks failed to observe sign-tracking, perhaps due to boredom and/or fatigue effects. Chapter Seven recruited participants from previous studies to complete the ASTT while undergoing functional magnetic resonance imaging (fMRI). Results revealed subcortical activations (namely in the striatum and other 'reward-motivation' structures) and correlations with sign-tracking, though sign-tracking was found to be unstable over time. Chapter Eight assessed the potential influence of covariates and confounds on signtracking; participants' gender, whether they believed they would obtain extra rewards for good task performance and cues' physical salience (regardless of value) were all shown to have no significant effect on sign-tracking as measured by the ASTT. Chapter Nine showed that sign-tracking is automatic/reflexive (as shown by quicker responses towards distractor cues compared to target cues), that distractor cues of different value attract attention with the same 'force' (as shown by identical reaction times [RTs] to the differently valued cues), and that the two measures of sign-tracking in the ASTT – RTs and omissions – do not consistently correlate. Chapter Ten reviews the methods, results, limitations and potential applications of this research. This thesis suggests that humans attribute incentive value to irrelevant, reward-associated cues, that this attribution can be exacerbated by low levels of alcohol consumption, is unstable over time, and is associated with activity in the subcortical 'value-driven attention networks'.
Supervisor: Rose, Abi ; Field, Matt Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral