Distinction_Between_Time_Based_and_Event_Based_Prospective_Memory

Discuss the Distinction Between Event-Based and Time-Based Prospective Memory In the past week it is almost certain that most people will have forgotten to carry out an intended action, whether it was to make an appointment at the dentist, return a call to a friend or buy some milk on the way home from work. Remembering an intention is known as prospective memory (Harris & Wilkins 1982) and studies such as Terry (1998) have shown that 50-80% of all everyday memory problems are in some way related to prospective memory. Developing a greater understanding of prospective memory is therefore crucial as problems in this area can have a seriously debilitating impact on a person’s life. Einstein and McDaniel (1990) proposed a distinction between event-based prospective memory (remembering to perform an action when an external event/cue occurs e.g. walking past a post box reminds us to post our friend’s birthday card) and time-based prospective memory (remembering to perform an action at a certain time or after a certain period of time has elapsed e.g. remembering to call a friend at 7pm as promised) however, Hicks, Marsh, and Cook (2005) suggest that there is not enough empirical evidence to distinguish sub types of prospective memory and Graf & Uttl (2001) claim they have not gained widespread acceptance in prospective memory literature. This essay will discuss the distinction between event-based and time-based prospective memory, drawing evidence from biopsychology and studies into aging and disease. It will show that although there is evidence to demonstrate differences between the two types of prospective memory, research results are very mixed and are yet to provide evidence of a clear distinction. It will also discuss limitations with the current experimental paradigms and suggest possible methods of researching in the future which may evidence a clearer distinction between the two types of prospective memory. The distinction between time-based and event-based prospective memory lies in the type of cue that triggers the memory that an action is intended and it is generally accepted that time-based tasks rely more heavily on self initiated cues i.e. there are no external cues to prompt the memory of the intended action therefore more continuous attention and concentration is required to monitor elapsed time (Einstein, McDaniel, Richardson, Guynn, & Cunfer, 1995). This is considered a more effortful process than event-based tasks which are prompted by external cues (Park, Hertzog, Kidder, Morrell, & Mayhorn, 1997) and is the basis of the theory that time-based and event-based prospective memory are activated by different cognitive processes. The two main theories that exist in relation to the cognitive processes involved, monitoring and spontaneous retrieval, appear to provide some evidence of a distinction between event-based and time-based prospective memory. Event-based tasks demonstrate a tendency to be retrieved spontaneously upon occurrence of the target event, ”There was no evidence that monitoring was necessary for producing high levels of prospective remembering,” (Einstein et al 1995 p.342) whereas an intention to do something at a particular time (a time-based task) will result in more monitoring of the environment for a cue for retrieval (Einstein et al., 2005). Marsh and Hicks (1998) claim that automatic processes generally remain intact with normal aging, whereas it is commonly accepted that self initiated processes decline with age (Craik, 1986). This would appear to predict that older participants’ results would decline in time-based prospective memory tasks in comparison to event-based tasks due to the increase in self initiated processes. This suggests that evidence for a distinction may be found in research of the effect of age on prospective memory. Only some research in this area has shown age differences between event-based and time-based tasks (Maylor 1993, Einstein & McDaniel 1996 and Einstein et al., 1995) whilst others have failed to find this distinction (Maylor 1990, & Einstein & McDaniel 1990) however, where a distinction was found, it was generally that the time-based tasks were performed less successfully than the event-based tasks. This appears to support the theory that the two types of memory are activated using different cognitive processes. Studies of the effects of age on event-based prospective memory have usually found no differences between the age groups (Einstein et al., 1995) supporting the theory of a more automatic approach to event-based prospective memory. The fact that there have been mixed results in these studies indicates that further research is needed in determining a distinction between time and event-based prospective memory. Einstein et al. (1995) suggest the lack of conclusive evidence is due to a lack of understanding in this area of research rather than a lack of distinction between the two types of prospective memory. Graf and Uttl (2001) agree and propose the research is still in its infancy stages and there are a number of other possible factors that could explain the age differences found. Craik and Jenning (as cited in Cabeza et al., 1997) point out that the speed at which information is processed (usually slower in older people) can have a direct effect on the performance of a cognitive task and Einstein et al. (1990, 1995) suggest age differences may be due to working memory load i.e. older participants are less able to maintain attention to the prospective memory tasks. In many of the studies, the younger participants were often college students and the older participants were not college educated which raises questions of general intellectual influence on results. Park et al. (1997) propose the differences found in time-based tasks may be due to errors made in monitoring the time rather than memory ability. This raises the possibility that rather than highlighting a distinction between the types of memory, the results are merely reflecting differences in cognitive processing and effort requirements. All of these factors highlight the complexity involved in determining the mechanisms by which prospective memories are retrieved. This makes the time-based and event-based distinction more difficult to clarify and leads to a necessity for research from a biological perspective on brain function. Using Positron Emissions Tomography (PET), which monitors blood flow in the brain regions, Okuda et al. (2007) found that time-based tasks and event-based tasks activated different parts of the brain. In time-based tasks, the left superior frontal gyrus was more active and in event-based tasks the rostral prefrontal regions were more active showing that each memory type demands distinctively different cognitive processing. Supporting this, Harrington, Haaland and Knight (1998) concluded the right inferior parietal cortex and superior frontal gyri play a role in time-based tasks but not in event-based tasks. This provides a strong indication that the two functions are controlled by different neural networks and appears to support a distinction between event-based and time-based memory, however, the main limitation with PET studies is there is no control over the thought processes of the participants. The brain region activity highlighted may not therefore, be solely related to prospective memory functioning. Further information regarding brain function can be found in studies into the effects of brain damage and disease on time-based and event-based memory. Shum, Valentine and Cutmore (1999) studied the effect that severe long term traumatic brain injury has on time-based and event-based prospective memory and found patients with brain injury performed slightly worse on time-based tasks than event-based tasks when compared to the control group. This appears to support the theory that there is a distinction between the brain regions involved with the two types of memory however could be explained by participants with brain injury having an inferior ability to estimate time. The control participants also performed less well on the time-based tasks than the event-based ones which as previously discussed could be the result of numerous factors. The study also demonstrated that participants with brain injury performed less well in all tasks than the control group making it difficult to show any distinctions in brain function between the two types of prospective memory. Brookes, Rose, Potter, Jayawardena, and Mording (2004) found participants who had suffered cerebro-vascular stroke performed more successfully at event-based tasks than time-based. Contrary to this, Maylor, Smith, and Della Sala (2002), established that participants with Alzheimer’s disease performed less effectively than the control group on both event-based and time-based tasks and Shum, Ungvari, Tang, and Leung (2004) found similar results with participants with schizophrenia. With the existence of all of the theories that support the prediction of inferior results in time-based tasks than event-based, the results of the study conducted by Katai, Maruyama, Hashimoto, and Ikeda (2003) become more crucial as they show participants with Parkinson’s disease to be impaired on event-based tasks but not time-based. Katai et al. presumed this to be due to frontal lobe dysfunction and further research built on this study could provide more robust evidence of a distinction in brain regions involved in event-based and time-based prospective memory. Knight (1998) however notes that the planning abilities of the executive functions required for prospective memory have been reported to be disturbed in patients with Parkinson’s disease again showing the difficulty in determining the precise brain functions involved. These studies have provided mixed data, some of which supports a distinction however the evidence is in no way conclusive. The dominant lab paradigm used for the study of prospective memory requires participants to remember to press a key in response to particular words they hear during a word recall test. The prospective memory is measured as the number of times participants remember to press the key in response to the cue (Einstein & McDaniel, 1990). Maylor (1996) notes that in all prospective memory tasks there is an element of retrospective memory i.e. remembering what the message was you had to deliver. Maylor states that as prospective memory is not an easily isolated act of cognition, the results of prospective memory tasks may not necessarily be revealing the functioning of the prospective memory component itself. This raises concerns that the laboratory paradigm is measuring an element of retrospective memory as the participants are required to remember the instructions of the task as well as the task itself. Attempts have been made to separate the retrospective element (Einstein, Holland, McDaniel & Guynn 1992) although until there is conclusive evidence that these strategies have worked, data supporting a distinction between time-based and event-based prospective memory must be read with caution as it is unclear how much influence retrospective memory is having on the results (Graf & uttl, 2001). An example of this, is the fact that patients with parkinson’s disease are reported to have impaired retrospective memory (Dubois & Pillon, 1996) and evidence from studies such as Katai et al. (2003) may need to be reconsidered when a more effective paradigm is proposed. Research conducted in naturalistic settings have not been successful in supporting evidence of a distinction between time-based and event-based prospective memory and have even contradicted previous research illustrating older adults perform better at time-based tasks than younger participants (Henry, Macleod, Phillips, & Crawford, 2004). Martin (1986) found that older participants were better at attending appointments (a time-based task) which contradicts much of the research in this field and suggests that to gain more conclusive data, a new experimental paradigm is needed. In everyday life, prospective memory tasks are achieved whilst engaged in a multitude of other activities and thought processes (Smith & Bayen, 2004) and new research using virtual environments is drawing on more modern technologies to account for these factors (Knight, Nicholls & Titov, 2008). Being more representative of the real world, virtual reality models may be able to eradicate some of the limitations of current paradigms and provide data giving a clearer understanding of the distinction between event-based and time-based prospective memory. This essay has discussed the existing research that attempts to determine a distinction between event-based and time-based prospective memory. It has shown that despite there being general acceptance of the different cues and self-initiated processes involved in the two types of prospective memory, there are limitations to the data which aims to support this distinction and it is not yet possible to draw conclusive evidence. Research from the biopsychology perspective has yielded mixed results, indicating that further research is needed to clarify a distinction between the two types of prospective memory. With the potential impact more knowledge in this area could have on the lives of people with memory impairments, it is a key area for further investigation and could be further developed in the future with new experimental methodology which can better control the confounding variables discussed. Until we have a greater understanding of the cognitive processes involved with prospective memory we are unable to make any definite claims.