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The modal model of memory is one of the most widely utilised and established models of memory research and subsequently memory research is still guided by its principles. Figure 6.1 below depicts an adapted version of the modal model of memory (Atkinson & Shiffrin, 1968) that pays homage to the two streams hypothesis. This adapted model has informed the development process and subsequent investigation presented in this research. This model was adapted to assist in investigating whether the capacities of the visual memory system vary and are dependent on the nature of the information being remembered.

To be able to explore whether there are differences in the capacities for each of the pathways, it was essential to develop a series of tasks that measure each of the components highlighted in figure 6.1. These tasks are outlined in Table 6.1.

Table 6.1. Summary of the Developed Assessment Tasks

Based on the research examined in the previous chapters, the preliminary phase of this experiment involved the development of tasks that could measure spatial and object memory separately. Therefore, prior to investigating capacity differences between spatial and object memory, Experiment 1 of this thesis involved the

development and piloting of a series of visual memory tasks. The general considerations that were acknowledged during development will first be discussed, before introducing each of the developed tasks that were created.

General Considerations

One of the dominant limitations that emerged consistently in the literature was that the measurement of visual memory has been methodologically constrained (Ciaramelli et al., 2010; Strauss et al., 2006; Lezak et al., 2012). At the time of the development, many prior assessments of visual memory acknowledged that the flexibility to express visual information dynamically, utilising a practical and portable approach, did not yet exist. While electronic media existed, developing assessments that

Spatial Tasks Object Tasks

Short Term Memory Spatial Span Object Span

Working Memory Spatial Working Memory Object Working Memory

Learning and Delayed Recall Spatial Learning Design Learning (Free Recall) Visual Pairs (Cued Recall)

utilised it is in its infancy and past attempts on desktop devices tended to be

cumbersome, difficult to standardise and lacked portability (Rensink, 2002). The tasks developed for use in Experiment 1 are hybrid tasks that involve electronic

administration with pen to paper response sheets. It was beyond the scope of the project to develop an electronic scoring system. As scoring assessments often requires a degree of subjective human interpretation, the decision to incorporate pen to paper response sheets was made. All participants had their own ‘participant pack’ that consisted of scoring sheets for the examiner, response sheets for the examinee and a data collation sheet for collating raw scores to aid in efficient data entry and analysis (see Appendix A.)

The stimuli designed for use in Experiment 1 were developed for use on tablet devices. This allowed the researcher the freedom to use any mode of presentation for the stimuli (static or dynamic) as well as enhanced the reliability of task administration, as all the timing for the stimuli presentations were built into the program. Memory tasks tend to be hypersensitive to any variation in administration procedures (Lezak et al., 2012), therefore, utilising software to ensure all administration was standardised, aimed to improve the reliability and the accuracy of the data collected. As tablets are portable devices, to ensure standardisation among participants all tasks were developed and administered for use on an iPad Pro 10.5 inch tablet. The iPad Pro had attached to it an Apple Smart Cover that allowed it to stand independently at an angle of 120 degrees to the viewer. For all participants the iPad was located 30cm away from where the

participant was seated.

Lezak and colleagues (2012) acknowledge that many tests of perception also measure other components of cognition, including but not limited to attention, spatial orientation, and memory. While tests of visual perception are generally better than tests

of visual memory at acknowledging the spatial/object demarcation, most current tests of visual perception have not focussed on reducing verbalisation, which has been found to impact memory performance in the past (Brown et al., 2014). Tests of perception also highlight the necessity of the role of attention. As previously discussed, attention is the necessary precursor for all higher order cognition, as without attending to the necessary stimuli no further processing can take place. In the same way, an intact visual

perception pathway is a necessary precursor to visual memory, as it ensures that all visual information is being processed and interpreted before being utilised by the higher order cognitive function. This reasoning gives rise to three predominant considerations.

First, the attentional demand required to comprehend and remember the

instructions needed to be low, as in tests with difficult instructions, performance tends to be affected (Wechsler, 2009). This is potentially due to an individual’s cognitive load dedicating substantial resources to remembering the instructions and subsequently being unable to devote the required attention to the task itself (Brown et al., 2014). In keeping with principles of test design, the tests designed in Experiment 1 included short,

succinct instructions accompanied with practice trials, to ideally reduce the demand required to comprehend the instructions, similarly to many of the established memory tests (Wechsler, 2009; Benedict, 1997).

Secondly, when constructing an assessment task it is important to ensure that it is difficult for a participant to succeed based on chance alone (Martin & Schroeder, 2014). In memory tasks where participants are asked to recall what they saw based on a discrimination/recognition trial the chances of guessing the correct answer are higher than in free recall tasks and this is dependent upon the number of options available. This is most often observed in recognition trials that only have two response items e.g. The Faces subtest in the WMS-III utilised a yes/no response system to complete the task.

Many participants produced inflated results as guessing provided them a 50% chance of getting the answer right. While such tasks are useful for identifying malingering

(Morgan & Sweet, 2009) in terms of accurately measuring an individual’s memory performance, results may be inflated due to the ability for a participant to guess correctly 50% of the time. While it is not always possible to develop free recall only tasks, in an attempt to prevent the ability of chance to inflate performance no

assessment tasks were developed that incorporated only two response items.

Furthermore, the lowest amount of responses an individual can choose from in any one task is in the initial spatial span and working memory trials, where an individual must accurately select, two, two response items in succession. While this is unfavourable, the likelihood that an individual would successfully select the correct pathway by chance is less than 25% (when the direction of the path is also accounted for) and this difficulty is only present for the initial trials. By the third span the likelihood of participants drawing the correct sequence by chance is reduced to less than 12.5%. In the object tasks,

participants in the initial trials must accurately select two correct items out of 8 possible responses. The likelihood of passing even the initial trials by chance is less than 1.7%. All assessments were designed to assess visual memory performance while controlling for a range of confounding variables, including performance inflation by chance.

Finally, one of the most important considerations involved stimuli design. As the tasks all involved visual stimuli it was important to develop a battery that encompassed a range of measures of visual memory, while also ensuring that the stimuli from one task did not interfere with the stimuli for another (Rademaker, Bloem, De Weerd & Sack, 2015). Thus, all abstract designs and the order of administration were carefully evaluated during this process to ensure that minimal interference between the tasks was present.

Based on the research examined and the general considerations above, Experiment 1 involved first developing a series of electronic assessment tasks that aimed to measure spatial memory and object memory function separately. While many measures of visual memory exist, cohesive measures that aim to provide a point of comparison for visual memory function are few and far between. It is with this notion that during development, known memory assessment paradigms were reviewed and where relevant applied to the visual memory tasks developed for this thesis. This process highlighted that individually many promising measures of visual memory exist, that are well designed and allow for investigation of memory function. A primary aim of this experiment was to adapt and combine current measures of visual memory to create tasks that can be administered utilising electronic media and incorporate what is known perceptually about the demarcation of spatial and object function.

The Developed Tasks

Note please find attached a quick reference guide for the developed tasks in Appendix B.

Where possible all span and working memory tasks were developed using the memory span paradigm i.e. consisting of a span task that aims to assess attentional control and capacity and a working memory task, that mirrors the span task in terms of stimuli design and task administration, however, contains an additional manipulation component. While the literature examined clearly highlights that visual memory

assessments should be developed through their own lens, many standardised procedures that are incorporated in verbal memory assessments are applicable for visual

information. All stimuli from the developed tasks are presented at a rate of one every two seconds. This is consistent with established measures of memory in both verbal and visual memory assessments (Wechsler, 2008; Milner, 1965). This allows a level of

standardisation and consistency to be present throughout the developed tasks.

Furthermore, all span and working memory assessment tasks consisted of two trials for each span. This ensures that participants are not penalised for a lapse in attention, and provides a more accurate depiction of an individual’s memory capabilities. Furthermore, this allowed both scoring and discontinue procedures to mirror those utilised in the robust established span tasks (Wechsler, 2008) as well as ensured consistency among the developed tasks. Finally, the stimuli designed for use in the working memory tasks and the administration procedures directly mirrored the stimuli and administration utilised in the span tasks. As the only difference between tasks is the inclusion of a manipulation component in the working memory tasks, this allows for direct

comparisons of performance to be made between the two tasks while controlling for variables related to stimuli design, and the perceptual demand for developing encoding strategies for new stimuli. Thus, any differences observed should be able to be

attributed to differences in memory performance.

Furthermore, the developed learning tasks drew administration inferences from established list learning verbal assessments, however, provided unique stimuli designs implemented to measure the various components of visual memory (Rey, 1964).The free recall tasks both contain five trials, where stimuli are presented in the same order each time at a rate of one every two seconds. This design aligns with both the

standardised procedures of the RAVLT and the developed span and working memory assessment tasks. No measure of interference was included in this series of tasks, this is due to this being a pilot study, and it was a greater priority to ensure that the tasks were capable of measuring the various components of visual memory in all stages of the learning process. The inclusion of an interference trial at this stage would have made identifying the causes of performance variance in the delayed recall tasks difficult to

discern. The delayed recall trials proceeded a 30 minute wait period which also aligns with the RAVLT. Finally, the cued memory task drew administration inspiration from Verbal Paired Associates. Similar to the past tasks stimuli were presented at a rate of one every two seconds.

The following section will provide evidence of what the developed tests involve, acknowledging the components that overlap with existing assessments or those that have been advanced through the use of electronic media, as well as noting what makes the developed tasks unique. There will also be commentary for how the stimuli were developed and the scripts used in the administration of each of the assessment tasks.

Spatial Memory Tasks

Spatial Span and Working Memory

Historically memory researchers have not explored the capacity of spatial memory in detail. To account for a severe lack of a comprehensive visual working memory assessment in children Gathercole and Pickering (2001) developed a series of visual and verbal assessments that together, made up the Working Memory Test Battery for Children (WMTB-C). One of the subtests included in this battery was a measure of spatial memory called Mazes Memory. During the development of the Mazes Memory task a static version and a dynamic version of the task were proposed, developed and piloted (Gathercole & Pickering, 2001). Several problems were identified with the dynamic mode of presentation. Firstly, it was not possible for a human to replicate the same clear, crisp lines that electronic media was capable of. More importantly, often the clinician’s arm and hand interfered with the child’s ability to see and commit the

emerging path to memory. Gathercole and Pickering (2001) reported that both versions showed promise, and thus, the final task became an amalgamation that incorporated

both modes of presentation. The stimuli for this task involved a series of rectangles surrounding a stick figure stimulus in the centre. Each rectangle had two small sections of the shape missing. These informed the participant of the possible exits for that section of the maze. As performance increased so did task difficulty with extra rectangles (walls) being added. While this task demonstrated good psychometric

properties for use with children (Gathercole & Pickering, 2001), adult norms were never developed. Similar to the RULIT and Corsi Blocks this task was also limited by the examiner’s ability to present dynamic stimuli. Building from the strengths and

weaknesses of this task the Spatial Span subtest was developed for use in Experiment 1. Rather than have participants complete the Spatial Span task backward, the manipulation component for Spatial Working Memory instead involved rotating the maze. Visual information has the ability to be manipulated in a three dimensional space as Shepard and Metzler (1971) who conducted a series of studies exploring the effects of mental rotation and spatial processing highlighted. They asserted that mentally rotating stimuli was a more cognitively demanding task than simply recalling

information in the same orientation. Neuro-imaging has also demonstrated that mental rotation tasks show activation in the prefrontal cortex indicating that some level of executive functioning (likely working memory) is involved (Shepard & Metzler, 1978). Based on the findings of their research in conjunction with the foundations established in the Mazes Memory task in the WMBT-C the Spatial Working Memory task was developed.

Stimuli Design

The stimuli design for this assessment was influenced from the design of the maze task in the WMBT-C (Gathercole & Pickering, 2001). When reviewing the stimuli

utilised in the psychometrically sound Mazes Memory task it was found that

components such as the length of the line, the rate at which the line was drawn and the number of turns involved were randomised rather than standardised. That is, different mazes included different line lengths, different turn directions and different amounts of ‘door skips’ (which is where the line goes past the initial door it reaches and bypasses to the second). While no pilot notes could be sourced on why these processes were not standardised it is suspected that this could possibly have occurred to prevent prediction based on previous trials. As the use of mazes is a long standing measure of memory e.g. the Morris Water Maze in animal research (Morris, 1984), Mazes Memory in children (Gathercole & Pickering, 2011) and the Groton Maze Learning Test in adults (Pietrzak et al., 2008), the standardised two dimensional, allocentric maze design was adapted and incorporated for use in this task. The image of the cat was selected for use to allow the user to orient where the top and bottom of the maze are located (this is particularly important in the working memory trial) (see in figure 6.2 and figure 6.3).

Spatial Span Outline

The Spatial Span task is a dynamic task that measures aspects of basic attentional control as well as an individual’s maximum spatial span when no manipulation is involved. This subtest involves a series of two dimensional mazes presented on a tablet device. Individuals are presented with a path that automatically appears from the centre of the maze outwards, on a tablet screen. The correct path is traced leaving a clear red line (6pt). Once completed the entire path remains on the screen for two seconds to allow for holistic consolidation before disappearing.

Immediately following the disappearance of the path, the individual is asked to redraw it using on the response sheet that is given in pen and paper form. The maze, with the path removed remains on the tablet screen, mirroring the response sheet. Every two trials, the maze increases in size. Mirroring Gathercole and Pickering’s (2001) maze task this involves another wall being added to the outside of the maze. While each maze has several possible routes participants are asked to draw the same path they saw

presented to them for a trial to be considered correct. Each wall consists of two possible exits that the individual can elect to take and selection of the incorrect exit will result in the response being incorrect. This task requires individuals to utilise free recall to demonstrate the correct route that was shown to them. This task is not timed and accuracy is the only factor that is measured. When a participant incorrectly completes two consecutive trials the task is discontinued. This task produces two scores. One score summates the number of trials an individual successfully completes correctly when the task is discontinued. The second score provides a measure of span and is determined by the number of walls present in the last span that the individual successfully completed both trials of (for example if an individual got both span 3 trials correct but then only one of the span 4 trials before discontinuing they would have a span score of 3). This

task consists of 14 trials ranging across 7 spans, thus, scores can range from 0 - 14 correct trials and 0-7 for span. (See Appendix C. for the examiners script)

Spatial Working Memory Outline

As highlighted above this task is a modified version of the span task that requires the use of spatial working memory skills. For this task the information is presented in the same manner as Spatial Span, however after seeing the pathway electronically drawn and vanish, this time the maze is rotated either 90 degrees, 180