Theoretical Models of event-based PM

Similarly to time-based PM, a number of theoretical models have been proposed to understand the underlying mechanisms that lead to successful event-based retrieval. According to Guynn (2003), in laboratory PM tasks, the monitoring

30 process involves a recognition check to evaluate whether the cue presented is the correct one for performing the intended action. If the recognition check indicates that the cue represents a target event then the intended action is executed. Failure to carry out the intention is therefore, due to the person’s failure to initiate a recognition check (in other words failure to monitor) or due to the failure of the recognition check to identify the event as a target. This theory is therefore based on two main assumptions; that monitoring processes require capacity demanding attentional processes and that monitoring processes are essential for prospective remembering to occur. If this is the case then the resource demanding processes required for PM will reduce the attentional resources available for performing ongoing activity and consequently lower the performance success of the ongoing task. This assumption is supported by a number of studies (Cohen et al., 2008;

Einstein et al., 2005; Marsh et al., 2003; Smith, 2003). A specific mechanism proposed to support monitoring is the supervisory attentional system (SAS;

Shallice & Burgess, 1991) which monitors for a cue signalling the appropriateness of executing the intended action. When a cue is detected the SAS switches attention to the intended action. This suggests that the realisation of an intended action is an attentional process supported by executive attentional systems and not memory processes per se.

By way of contrast, McDaniel and Einstein (2000) proposed a different multiprocess theory suggesting that because of the PM demands in everyday life it is adaptive to have a cognitive system to aid PM retrieval through several processes. So, in addition to the resource demanding processes such as monitoring, prospective remembering can sometimes be spontaneously elicited by

31 features of the target cue even without resources dedicated to the intention.

McDaniel and Einstein (2004) maintain that this spontaneous retrieval in event-based PM can involve a number of processes such as the reflexive-associative hypothesis, in which the cue is strongly associated with the intention during planning and the intention is performed reflexively.

In relation to this, Guynn, McDaniel and Einstein (2001) proposed an alternative to conscious cue-focused account based on a memory model proposed by Moscovitch (1994); an “automatic-associative” memory system that consciously attends to external cues which in turn interact with memory traces previously associated with those cues. If there is enough interaction between the external cue and a memory trace then the system delivers awareness of the information associated with the cue, thus mediating PM retrieval. As opposed to cue focus theory, the target event is not necessarily recognised as a cue; it simply stimulates a reflexive associative process bringing the intended action into awareness. The entire pattern implicates both cue-focused and reflexive associative process and more generally supports a multidimensional framework of PM (McDaniel and Einstein, 2000).

As previously discussed, some researchers argue that PM declines with age and a number of experiments using event-based PM to appear support this assertion (see review Henry et al., 2004). However, other studies report no age differences in event-based PM (Einstein and McDaniel, 1990). In an attempt to understand this anomalous pattern, Einstein and McDaniel (2005) used the multiprocess point of view and suggested that age differences depend on whether the PM task uses focal

32 or non-focal target events. According to Einstein and McDaniel (2005) a focal PM cue is the one that stimulates the spontaneous retrieval of an intention without the need to employ strategic monitoring processes. With non-focal targets attention-demanding processes (i.e., monitoring) are essential for prospective remembering and according to Craik (1986) these resources decline with age. Conversely, focal targets require spontaneous retrieval which is assumed to stay relatively intact with age. To support this assumption, Rendell and Craik (2000) found minimal age-related declines in event-based PM when the event was focal. In contrast, when the event was non-focal the age differences were more pronounced.

According to McDaniel, Guynn, Einsten and Breneiser (2004), spontaneous retrieval, as opposed to monitoring, can occur even when no resources are devoted to monitoring for the target during or prior to the occurrence of the target. To support this, Einstein et al.’s (1995) results from a study comparing performance on event-based PM tasks between older and younger adults suggest a large automatic component to event-based PM. Marsh and Hicks (1998) suggested that these mixed findings can be explained by the character of the demands that the tasks place on working memory and that poorer event-based PM performance depends on an attention demanding component and therefore might be correlated with measures of central executive functioning.

To support this view, the notice-search model (Kliegel et al., 2001; Logie et al., 2004) has also been proposed. This model suggests that for successful PM, familiarity and probe search are required. When people encounter the PM cue they get a sense of familiarity (noticing) which may then prompt a more conscious

33 probe of memory (search) to determine what the cue means. Therefore, there are two stages in a successful event-based PM task: the stage of noticing or a feeling of familiarity and the search stage. Burgess (2000b) suggested that PM task completion requires many of the skills that are commonly described as executive processes. Successful completion of intentions rely on the operation of a number of different cognitive processes including attention, action control and memory (Dobbs & Reeves, 1996; Ellis, 1996). In particular the literature on PM addresses an important debate on the attentional or strategic demands of PM task retrieval evaluating the notice-search (strategic component) and automatic activation models. According to West and Craik (1999) older adults are more prone to lapses of intention and are believed to suffer from attentional or executive deficits. These failures are associated with changes in neural activity in a region thought to be responsible for the implementation of cognitive control. It is therefore reasonable in order to further understand the underlying mechanisms of PM to look at changes in neural activities during the realisation of PM tasks.