Effects of pro-social motives and reward on children's prospective memory and inhibitory control

Prospective memory (PM) refers to the ability to remember to perform an intended action in the future whereas inhibitory control (IC) is defined as the capacity to stop a prepotent or automatic response in favour of a more correct or pertinent response in a certain situation. The main aim of the present thesis was to investigate the role of motivational factors – such as the social values of goals and presence of rewards – in children’s PM and IC abilities by using an event-based PM task (EBPM) and a RI task (Go/No-Go) modelled after Brandimonte et al. (2011). RI plays a pivotal role in executive control (e.g., Andres, 2003; Aron, 2007; Logan, 1985a; Miyake et al., 2000; Stuphorn & Schall, 2006). RI concerns the ability to withhold responses that are unsuitable or not useful, so facilitating behaviour that is both flexible and goal-orientated in constantly changing environments. RI ability is called upon frequently in everyday life to prevent us from committing potentially harmful actions, for example, from stepping into the road when a car comes around a corner without seeing you. Go/No-go task is typically used in order to measure RI ability. Only two types of stimuli are used in the conventional Go/No-go task: a Go stimulus, and a No-go stimulus. Instructions are given to participants to respond rapidly, usually by pressing a button, only when Go stimuli appear, whereas they have to refrain from pressing the button on the presentation of No-go stimuli; response inhibition refers to the ability to stop oneself responding to No-go stimuli. Usually, Go stimuli appear more frequently in this kind of task, such as to predispose a participant to responding and increase the amount of inhibitory effort needed to not respond when presented with No-go stimuli (Simmonds et al., 2008). Performance in RI paradigms can be thought of as an independent “horse race” in which there is a go process prompted by go stimuli, and a stop process prompted by No-go stimuli (Logan & Cowan, 1984; Logan, Van Zandt, Verbruggen, & Wagenmakers, 2014; Verbruggen & Logan, 2009b). RI is successful when the stop process is underway before the go process and no response is made (signal-inhibit); when the go process starts before the stop process, response inhibition is unsuccessful as a response is made inappropriately (signal-respond).This choice wase made because these two tasks mentioned above seem to involve two types of intention that differ with respect to the direction of the intended action. While both the EBPM and RI tasks require forming, maintaining, and realising delayed intentions, the EBPM task involves the overt execution of the intended action, while a response inhibition task necessitates the suppression of the predominant response (Brandimonte et al., 2011). In summary, these two tasks could be considered as being in parallel in all respects apart from the response direction, as the former consists of remembering to perform an action, whereas the latter involves refraining from acting. Of particular importance are the EF abilities needed for each task type; task-shifting abilities are predominantly required during EBPM tasks when a participant must switch from the ongoing activity to the execution of a certain action when a target cue is seen. The RI task, by contrast, principally involves inhibitory control abilities, as the participant must remember not to perform the ongoing activity when a target cue appears. Despite this contrast, switching an inhibition are not mutually exclusive; switching is still involved in an RI task, inasmuch as the participant switches from the task of performing (ongoing), to the task of not performing (RI – no response). Nevertheless, the pivotal role in the RI task is played by the active suppression of actions that would be counterproductive to the achievement of the predefined goal of the task. This comparison of RI and EBPM tasks applies particularly to these two kinds of task, as both of them involve performing two types of task simultaneously, that is the ongoing task and additionally either the PM or the RI task. However, the same comparison cannot be made between TBPM and RI tasks, since the TBPM is not based on the appearance of a target cue, which however does occur during the RI and EBPM tasks. Indeed, in TBPM tasks, intentions must be executed only after a certain period of time has passed or at a predetermined point in time in the future (Wang et al., 2008); for example, recalling the need to take medicine at a given interval, or remembering to call a friend on their birthday. By contrast, in EBPM tasks an external cue should in theory remind the participant to perform the intended action (Talbot & Kerns, 2014); examples include remembering to pass on a message to a friend when they are next seen.Overall, the present research includes three large studies testing children aged 4-5 years, 6-7 years, 7-8 years, 10-11 years, and an adult group. Specifically, the following research issues have been explored: a) whether motivational factors, such as pro-sociality and reward, can have effects on children’s memory for intentions and response inhibition (RI) and, if any, b) whether these effects differ as a function of task (PM and RI); c) whether children’s PM and RI performance differ from that of adults when pro-sociality is involved. Results highlighted a significant interaction between Pro-sociality and Task, indicating that children had worse PM performance under the condition with pro-sociality (Study 1). In contrast, pro-sociality improved adults’ but not children’s performance (Study 3), as qualified by a significant interaction between Pro-sociality and Age. Significant effects of Reward emerged when Task factor (Go/No-go task / PM task) was partialled out (Study 2), showing that children performed better in conditions with a reward but only in the Go/No-Go task. A significant effect of Task was found in Study 2 and Study 3, such that participants had higher scores in Go/No-Go than in PM tasks. In conclusion, this Ph.D. project adds to the evidence that while PM and IC may have some commonalities because they are both linked to intentions (to do something or not to do something), they seem to rely on different mechanisms as indicated by the differential effects of Task, Pro-sociality, and Reward