Paper introducing the methodology of the similarity index in field studies

Early in my post-doc project, our research group was contacted by an emergency control centre in a major oil company. The centre handles incidents on offshore oil and gas rigs, events like fires or gas leaks, heavy weather or ships on collision course. The centre's task is to construct a coherent image of the emergency based on the incoming information, and to advise and organize the different resources involved in handling the emergency. The centre wanted our help to identify areas for further improving their emergency handling.

My initial approach to the request was to develop measures for individual and team mental representation. That is, does each team member have a good idea of what's going on at the oil rig, and does the team as a whole have a good idea of this? However, it quickly became apparent that since both actual events and training exercises in this setting are non-transparent, dynamic and interactive, it would be challenging to establish a ground truth for what the different team members should be expected to know at different times through an exercise.

We arranged a series of unstructured and semistructured training exercises for all the emergency teams in the organization. At planned intervals we "froze" the exercise, and had all team members answer questions about the situation and the team's work. But the challenge remained of how to assess the responses of these questions. The experts were reluctant to say that a given team member should hold a given bit of information about the situation at a given point in time.

The solution I chose was to compare the answers between the team members. I developed two algorithms that were applicable to all the questions. The first of these returned a value from 0 to 1, indicating how similar your answer was to the rest of the team. The second returned a value from 0 to 1, indicating how similar your answer was to the team leader. I argued that the first calculation should approach a measure of shared mental models, that is, the extent to which the team member had the same representation of the incident as the rest of the team. The second calculation should approach a measure of situation awareness, as a higher score should be associated with more accurate knowledge, given the assumption that the team leader was the best informed member of the team.

As this was a fairly (though not completely) novel methodological approach, before going any further we published a paper that went into some detail on describing the measures and the calculation of the scores. This was published in Journal of Cognitive Engineering and Decision Making: The similarity index as an indicator of SMM and SA in field studies. This paper did not test any research hypotheses, as this was reserved for future papers.

Book chapter on situation awareness applied in maritime settings

In 2013, our research group "Operational psychology research group" and associated members collaborated on an edited book called "Motivating for safety". The book was intended for practitioners in the industry, in particular captains and safety officers in the maritime field. The book covered topics such as safety climate, sleep deprivation, shared mental models, situation awareness, leadership, psychological capital and hardiness. Each topic is illustrated with cases, exercises and training questions. My chapter on situation awareness is linked below.

Motivating for safety - Chapter 6 - Seeing, understanding, anticipating - Situation awareness as a requirement for safe voyages

Paper on assessment of conscious states

How can we tell whether an immobiised patient is conscious or not? This was the starting point for the master thesis of three clinical psychology students that I supervised. The students reviewed and provided a synthesis of the recent scientific literature on the subject. After the thesis work was over and the students had left the university for clinical positions, I collaborated with them to rewrite the work into a article intended for Norwegian clinicians.

Table 1:

STATE OF  CONSCIOUSNESS	WAKEFULLNESS	AWARENESS	INTENTIONAL BEHAVIOUR
Normal awake state	Yes	Yes	Yes
unresponsive wakefulness syndrome	Yes	No	No
Minimally conscious state	Yes	Occasionally	Some
Locked-in-syndrome	Yes	Yes	Very limited motor capacity
Coma	No	No	No

The paper gives a definition of consciousness and outlines the clinical disorders of consciousness (see table 1 above). We then categorise four different types of assessment of consciousness: behaviour checklists, electrophysiology, imaging of activation and imaging of networks. We discuss each approach's standing, merits and disadvantages (table 2). Finally we discuss to which extent the assessment approaches reflect the theoretical definition.

Table 2:

APPROACH	TYPE	EXAMPLES	PRINCIPLE	ADVANTAGES	DISADVATAGES
Behaviour checklist	Active or passive	GCS-R, SMART, etc., see Seel et al. (2010) for review	Checklist for whether actions occur, spontaneously or on instruction	Has clinical standard	Unable to capture consciousness that does not appear in the behavior
Electro-physiology	Active or passive	EEG, ERP	Electrodes measure simultaneous fireing of groups of neurons	Equipment readily available can be used on all patients, also at bedside	Hard to say where the signal comes from, hard to say which processing the response involves
Imaging of brain activity	Active	fMRI, PET	Imaging of the metabolism from activity in different parts of the brain	Good localization of the signal, can determine whether a task activates the same areas as in healthy people	Expensive and scarce equipment, cannot be applied to all patients. Measures the capacity for consciousness, but this capacity is not necessarily in use
Imaging of networks	Passive	Default mode network, DTI	Measures which parts of the brain that are connected, or that are activated simultaneously	As above, but does not require active participation from the patient	As above, but in addition it is unclear how the networks should be interpreted

As we wanted to inform Norwegian clinicians working in adjacent fields and next-of-kin to patients with consciousness afflictions, we wanted the paper to be easily accessible. We published in a peer-reviewed Norwegian online open-access journal (abstract in English)

Link to the publication in psykologisk.no (Scandinavian Psychologist).

The "updating" component of WM is differently involved in various noise conditions

Several years ago Patrik Sörqvist and I collected fMRI recordings of participants performing a working memory (WM) task, where WM content updating could be compared to WM maintenance. Soon thereafter we published a paper on the data from the pilot sample of eight participants performing the task in silence.

In addition to examining WM mechanisms, we also wanted to study how the WM functions in different auditory noise conditions. Therefore the majority of the participants performed the task while different noise conditions were played in the background. However, this was not part of our initial publication, and both Patrik and I got involved in other projects, preventing us from publishing on this aspect of the study until this year.

We found that the larger data set (from 18 participants) confirmed the main finding of the pilot study: that updating WM content activates areas mainly in dorsolateral prefrontal cortex, the posterior medial frontal cortex and the parietal lobes (shown in red in the animation below, t-values 7-16), while rejecting the input and not updating WM content activates the anterior medial frontal cortex (shown in blue). Comparing this to the similar contrast in our previous publication shows a very similar pattern, indicating a replication of the finding.

In order to address our second research question of how noise affects WM function, all participants performed the study in three different conditions: In silence, in aircraft noise and in speech noise. We wanted to see whether updating WM content in speech noise activated different cortical areas than updating in aircraft noise. As shown in the animation below (t-values 4-9), the prefrontal cortex is involved to a greater extent when updating in speech noise (shown in gold) than when updating in aircraft noise (shown in silver). This could indicate that speech noise is more intrusive on e.g. phonological loop processes, and requires deliberate processing to counteract.

The publication is currently in press at Scandinavian Journal of Psychology. You can find a pdf of the pre-print version of the paper here. The publication is currently in press at Scandinavian Journal of Psychology. You can find a pdf of the pre-print version of the paper here.

ERP paper on sequential effects of selective attention (Primed DL)

During my ambitious young PhD years in cognitive neuroscience I collected more data than I had time to publish on. For example, I equipped participants with 61 scalp electrodes and let them perform the "primed dichotic listening" experiment that I had developed. My previous studies had established a priming effect, and fMRI neuroimaging had indicated that cognitive control and inhibition may be involved in producing the effect. As ERP has a finer temporal resolution, this could be used to examine the time course of such an effect. Unfortunately, I didn't have time to analyse the data during my PhD time, so the data was left unused for several years. I later got in touch with René Huster whom I went to graduate school with, and we analysed the data together during a research visit to his research group in Oldenburg.

As before, in each trial of the experiment a single syllable was played followed by a dichotic syllable pair, and in some cases one of the syllables in the pair repeated the prime syllable. The trials were categorized based on whether the repeated syllable was selected or not, as shown in the figure below.

A strong behavioural effect was seen as in the previous studies. The ERP analysis was optimized to identify differences in the early attention processing (i.e. the N200s) between the different response categories. ERPs were extracted for three midline electrodes from four relevant time-windows and compared between the conditions using repeated measures ANOVA. Significant effects were seen in both the prime-related (left in the figure below) and in the dichotic target-related activity (right in the figure below). 

Trials where the participant reported the non-primed syllable (prime ignored trials) showed more negative ERPs at prime presentation, which may indicate inhibition of the prime representation. Trials where the participant reported the primed syllable (prime reported trials) showed more negative ERPs at target presentation, which may indicate cognitive conflict and effortful response selection. In reference to the theoretical framework presented previously, the data suggest that the interplay of a proactive inhibition bias (during prime presentation) and a reactive potential for conflict (during target presentation) is involved in causing the primed dichotic listening effect.

Sætrevik, Huster & Herrmann (2013) Proactive and reactive sequential effects on selective attention - Brain and Cognition

There is also a second data set, with EEG recorded from a larger data set doing a sequence of dichotic listening trials which we will hopefully go on to publish some day.

Suggesting a context-general survey for situation awareness

One of the aims of my post-doc was to develop a measurement approach for situation awareness (SA) that could be applied across different settings, and can be used in large data collections. Endsley's theoretical model suggests that SA consists of three levels - perception, understanding and prediction, and should be measured with instruments adapted to the setting in question.

Based on a theoretical review, I developed and piloted an inventory of 13 items, which were then tested on a larger sample of 166 sailors. To test whether the inventory supported the theoretical model for SA, two different confirmatory factor analyses were run, one where all items were associated with a single factor, and one where the items were associated with three factors.  The three factor model showed a good fit with the response patterns.

Thus the approach appears psychometrically valid, although it remains to see whether it has any predictive value. Further, some researchers may be reluctant to measure SA in the same way across contexts. The article was published in a special issue of International Maritime Health.

Link to paper: Sætrevik, B. (2013). Developing a context-general self-report approach to measuring three-level situation awareness. 

Poster on emergency preparedness center teams for stakeholder seminar

In September 2012, the research group I was part of arranged a stakeholder conference for our industry partners and other stakeholders in the maritime and offshore business. Formal organizer of the conference was the marine insurance company Norwegian Hull Group, and the overall theme for the conference was "safety climate".

Our research collaborators Jarle Eid, Rhona Flin and Fred Luthans had oral presentations at the conference. I presented a poster on the shared situation awareness in teams field study described in previous posts. The poster is available here: Emergency preparedness center poster

To zoom around the different sections of the poster, use the Prezi below:

HFES conference paper and presentation on shared beliefs in emergency center teams

Towards the end of my post-doc period, I presented my field study work at the 56th annual conference of the Human factors and ergonomics society (HFES) in Boston in 2012. The presentation consisted of a 20 minute presentation and a five page conference paper, both posted below.

The work argues that efficient handling of critical situations relies not only on the availability of information, but also how the information is transferred and distributed within the team. In the presentation I lay out some of the challenges to measuring "situation awareness" for team members in realistic settings. I suggest that it may be fruitful to compare the beliefs of the various team members working together and estimate to which extent they match up. I present a rough description of one of my field experiments, where I worked with the emergency preparedness center of an offshore oil company. Five teams ran a realistic training scenario for 2-3 hours, and the scenario was frozen at nine time points where the team members had to answer how confident they were about their information handling and what they knew about the situation. Heart rate variability was measured for all team members throughout the scenario. 

The results show that team members were quite confident, their confidence rose early in the scenario and remained stable throughout the scenario. However, the confidence was not related to what they actually knew about the scenario, which was lower and varied more across time. High frequency variability in heart rate can be taken as an indicator for cognitive adaptability. Results showed this to covary with less complex phases of the scenario. As this work was ongoing at the time of presentation, the oral presentation results are more complete than the results in the paper. Also note that the calculation of both shared knowledge and HRV have changed since this point in the analysis.

Conference paper: A controlled field study of SA in emergency handling teams

Conference presentation:

Distinguishing the "updating" component of working memory

A memory system must be able to serve at least two functions, to hold information over time, and to change the information that is being held. While several studies have identified a vast cortical network to be involved in working memory, little work has tried to distinguish the two different functions.

In 2008 I came into contact with Patrick Sörqvist, then a PhD student from an applied psychology lab in Gävle, Sweden, who was interested in practical implications of memory systems. He wanted to run an fMRI study of the number updating task, which can distinguish the points in time when working memory content is being updated, as opposed to when the content being held constant while ignoring new information. I helped out with experiment design, programming, fMRI analysis and write-up. We found some cortical regions to be more activated for memory updating than when not updating, and other regions to be activated in the inverse condition.

Sörqvist & Sætrevik (2010) The neural basis of updating: Distinguishing substitution processes from other concurrent processes - Scandinavian Journal of Psychology

We probably used the wrong heatmap shading for the fMRI activations shown in Figure 1 and 2, as they did not come out well in the black and white print. They were supposed to look more like this:

Figure 1: Areas more activated when updating.

Figure 2: Areas more activated when not updating.

Here are the same activations shown in an animated glass brain. Areas more activated when updating are shown in "hot", areas more activated when not activated are shown in "cold" (t-values 6-16 are shown).

The study had quite few participants, but we later supported the main finding in another study with more participants (currently under review).

Transient activation of speech areas following language task

My fMRI study of primed dichotic listening from 2009 showed that stimulus conflict increased medial prefrontal activation, and response conflict increased left dorsolateral activation. That went some way in terms of figuring out which mechanisms are involved in the task, and we accounted for it in terms of the Desimone and Duncan's biased competition model and/or Botvinick's model of interaction between cognitive conflict and control.

After publishing this work, I started thinking whether the data could also be used to understand how the mechanisms interacted. Some recent studies have indicated that high cognitive conflict on one trial leads to  increased cognitive control on the following trial. The increased control is typically seen as faster and more accurate performance, and increased activation in cortical areas assumed to hold the task set instructions. Could I do something similar with my task? Given that I had formally left the neurocognitive research group at this time, I was perhaps also motivated to get the most out of my already collected fMRI data.

The 2009 analysis had analysed according to what the current stimuli and the current response was. The new analysis restructured the data file according to whether the previous and the current trial was high (prime repeated in targets) or low conflict (no prime-target repetition). This yielded four different categories (previous trial - current trial):

1. High - high
2. Low - high
3. High - low
4. Low - low

From this we could run two different analyses: In the first contrast, we compared sequence 1+2 with sequence 3+4, i.e. examined what the effect of the current trial was, regardless of what happened on the previous trial. As expected, this yielded much the same result as the 2009 analysis, showing that task conflict activates medial and dorsolateral prefrontal areas. The second contrast compared sequence 1+3 with sequence 2+4, i.e. examined what the effect of the previous trial was, regardless of the current trial. This showed that following a stimulus conflict, activation increased in temporal areas, more on left than on right side. No behavioural after effect of conflict was seen, perhaps since there is no defined correct answer in the prime dichotic listening task (both syllables are correct, and error rates are low), and response times were not measured. 

In line with current models for how cognitive conflict modulates cognitive control, we interpreted the effect as challenging task leading to more resources being dedicated to the type of processing involved in the task, in this case discriminating verbal stimuli. The fact that sequential effects showed temporal rather than e.g. dorsolateral activation, may indicate that conflict did not lead to increased task or instruction focus, as has been seen in e.g. sequential effects of Stroop tasks, perhaps as the task is rather simple. 

  

My by then former college Karsten Specht helped me with the analyses and the manuscript, and we published this in "Brain and Cognition" in 2012. A lab meeting presentation of this study can be found here. 

Cognitive conflict in a syllable identification task causes transient activation of speech perception area of speech perception area - Brain and Cognition

Dichotic listening for vowel-consonant syllables

This project stands out from my main projects, and aims to explore the generalizability of a popular experimental approach, rather than theoretical development. The design is simple and the paper is short with unsurprising results, although I think it provides necessary clarification to otherwise unanswered questions.

In our lab (and I think also a lot of other labs) we use a number of different variations of the dichotic listening (DL) task, but we tend to use a standard set of stimuli, namely the nonsense syllables constructed by the six stop-consonants followed by the vowel "a", constituting the consonant vowel, or CV syllables: BA / DA / GA / PA / TA / KA. When presenting one of these CV syllables in one ear simultaneously as a different CV syllable in the other ear, participants tend to report the CV syllable presented in the right ear, an effect referred to as the right ear advantage (REA). This effect is explained as left cortical hemisphere having an advantage in language processing and sensory fibres going from each ear to the hemisphere on the opposite side. Studies using DL with CV syllables have been used to explore both attentional effects and clinical groups. However, DL is often used in arguments concerning language in general, although the task only uses a small subset of the language phonemes. In this project, I wanted to test whether the REA could also be found when using different kinds of syllables. I also wanted to see how different types of syllables are selected between when presented simultaneously.

I constructed new stimuli, some with the same CV structure as in earlier experiments, while others used the same consonants and vowels, but in reverse order, i.e. vowel-consonant (VC) syllables. Both types of syllables were paired up in all four left-right combinations: CV-CV, CV-VC, VC-CV and VC-VC. Participants were asked to report which consonant they heard. Results showed that the REA was found both for CV and for VC dichotic pairs, thus showing that that the typical assumptions behind DL can be extended to a wider array of phonemes than just the CV syllables. Further, when CV is presented in one ear and VC in the other, CV has a perceptual advantage. In the paper's discussion, I go through some of the research from the sixties and seventies when different types of stimuli were used in DL, and see to which extent they showed a REA.

The right ear advantage revisited: Speech lateralisation in DL using CV and VC syllables - Laterality

Selective attention, positive and negative priming in a sequence of dichotic listening trials

In the early years of my Ph.D., I wanted to do an ERP study of my basic primed dichotic listening paradigm. My supervisor Kenneth Hugdahl and my collaborator (and unofficial supervisor) Tom Eichele wanted me to do an ERP study of a standard dichotic listening task first, so we went ahead with that. Participants sat in a comfy chair with electrodes pasted on their scalp and did sequences of dichotic listening trials for 40 minutes. A short beep at the beginning of every trial directed attention to the left, right or both ears, then two different syllables were played at the same time, one in each ear, and the participants were to indicate what they had heard. However, when the results came in, we weren't able to make sense of the results. The EEG results didn't show the lateralized effects we had expected, and the behavioural effects of attending to the instructed side were not as clear as we had expected, so we eventually abandoned the study.

Some years later, after developing my ideas about priming using other behavioural studies, I wanted to test whether I could design a study to show both positive and negative priming effects to interact with instructed attention. I would need a largish dataset in terms of number of participants and trials order to tease out what could be rather weak effects. It then occurred to me that I already had such a dataset sitting on my hard drive, so I picked up the behavioural data from the ERP dataset, and applied analyses to it according to the new theoretical model.

The results section is somewhat complex as it tests for five different hypotheses. Basically this paper reproduces some of the effects shown in previous papers (overall inhibitory selection effects of repetition, negative priming of decreased likelihood to select a recently ignored stimulus, and priming effects interact with instructed attention), as well as showing some novel effects predicted by the model (positive priming effect of increased likelihood to select a recently attended stimulus, interaction between priming and instructed attention is demonstrated in a sequential dichotic listening task). As opposed to what competing theoretical models of priming would have predicted, the selection criteria on the prime trial did not influence the priming effect.

Sætrevik (2012) Facilitating and inhibiting effects of priming and selection criteria in a sequence of DL trials - SJoP

The effect of simultaneous visual stimuli on dichotic listening selection

This study was more or less a side project that does not quite fit in to the rest of my dichotic listening studies. The aim was simply to see if the dichotic listening selection would be influenced by simultaneous ecological visual stimuli. I made brief videos of a mouth pronouncing each of the six syllables, and played one of them simultaneously as the audio for the same syllable was played in one ear, and the audio of another syllable was played in the opposite ear. Participants were asked to report which sound they had heard. Unsurprisingly, the video presentation had the effect of increasing selection of the audio stream that matched the video.

In a way this study was the opposite of my priming studies: Rather than manipulating the selection between two equally valid simultaneous stimuli, the current study made one of the simultaneous stimuli "more valid" by adding a visual channel of information. The effect is reminiscent of the McGurk effect, but in this case it does not create a new percept, it simply "tips the scales" to select one rather than the other.

Sætrevik (2010) The influence of visual information on auditory lateralization - SJoP

Negative priming in a sequence of dichotic listening trials

The previous studies had shown that presenting a single syllable that the participant was supposed to ignore made it less noticeable in an immediately subsequent pair of dichotic syllables. However, the rather artificial experiment situation allowed one to questions of the effect's generalizability. Further, we don't really know what the participant is doing when instructed to "ignore the first sound". According to my theory, the negative priming effect should appear in any situation where a recently ignored stimulus is repeated. As classical theories considered the dichotic listening situation in itself (an information funnel where two bits of information enter and one come out) to be resolved by attenuating one signal but also inhibiting the other signal, it occurred to me that I could simply loop the process, and make one dichotic selection constitute the priming process for the next dichotic selection, which could again prime the next dichotic selection and so on.

Thus, as the dichotic listening paradigm used in our group presents one syllable to be attended and one to be ignored, I could leave behind the somewhat convoluted prime-target task design I had used in my previous studies, and simply present a sequence of dichotic listening trials (without any attention instruction). I adjusted the on-line randomization of stimulus selection to make sure that 50% of the trials repeated one (but not both) of the stimuli presented on the previous trial. In the analysis of the trials with repetitions, I considered every trial n to be the prime for trial n+1. Whether the repeated prime syllable was expected to have a negative or positive effect on n+1, depended on whether the participant selected to attend it or not (for whatever reason) on the prime trial n. E.g., if trial n presents the syllables "Pa" and "Ta" and the participant selects "Pa", then "Ta" was considered to have been inhibited, and if trial n+1 presented "Ta" and "Da", then "Ta" should have a reduced likelihood of being selected. The results did indeed show such a negative priming effect. A converse positive priming effect was indicated, but failed to reach significance (although it was shown in a later study).

The main contributions of this study was (1) to show that sequence effects are apparent in even rather simple dichotic listening tasks without any convoluted priming procedure, and (2) that negative priming effects could be seen in a sequential task with free choices where the prime selection is made arbitrarily. This second point has some relevance for theoretical development, since at least some reading of previous negative priming theories stated that the prime selection would have to be based on a pre-defined selection criteria in order to cause subsequent negative priming effects. I began to formulate what I consider to be a more parsimonious model to account for priming effects, where different nodes in a network achieve different levels of activation based on the stimulus input, but also retains positive or negative activation from preceding selection.

Sætrevik (2010) A biased competition model accounts for negative priming in a free choice situation as residual effects of inhibitory conflict resolution - Neuroscience Letters

Ph.D. thesis on cognitive control in auditory processing

This is my Ph.D. thesis dissertation for the University of Bergen named "Cognitive Control in Auditory Processing". The dissertation details the research process behind my project with developing the "primed dichotic listening" task. The dissertation contains three papers, one published in Neuropsychologia, one published in Neuropsychology, and one that was later published in Brain and Cognition. The additional dissertation text covers a more extensive theoretical background (on attention, priming and dichotic listening), methodological details and implications.


Sætrevik, B. (2008). Cognitive Control in Auditory Processing (Doctoral thesis No. ISBN 978-82-308-0570-1). Bergen: The University of Bergen.

fMRI study on primed dichotic listening

In the third and final paper in my PhD, we repeated the primed dichotic listening experiment from the two previous papers in an fMRI setting. We found response choice and RT comparable to the previous studies. One analysis compared the activation on trials that repeated the prime to the activation on the trials that did not, and showed increased activation in medial frontal gyrus and in right inferior frontal gyrus (IFG). This was associated with the cognitive processes of cognitive conflict and inhibition, respectively. A second analysis compared the trials where the repeated syllable was ignored to the trials where the repeated syllable was attended. Ignoring the repeated syllable (the response bias) correlated with right IFG activation, while attending the repeated syllable correlated with cingulum / frontal gyrus and IFG activation. This was accounted for by associating one response pattern with inhibition, and the other to increased conflict and decision making.

Satrevik & Specht (2009) Cognitive conflict and inhibition in primed dichotic listening - Brain and Cognition

Paper on interaction between priming and directed attention in dichotic listening

In the second paper in my PhD, we presented a prime syllable that participants were instructed to ignore, followed by a dichotic syllable pair. In the first part of the experiment, the participant was asked to report the syllable heard best overall, while in the second and final part of the experiment, the participant was asked to report the syllable heard in the left or the right ear. The results showed

1. the same negative priming effect as reported in the previous paper,
2. an effect of directed attention and
   
3. an interaction between priming and directed attention.

It was argued that the study showed that the two types of attention modulations could coexist, while the interaction indicated that the two may have some overlapping cognitive features.

Sætrevik & Hugdahl (2007a) - Endogenous and exogenous control of attention in dichotic listening - Neuropsychology

As a methodological aside, this paper presents the responses analyzed in three different ways:

1. in terms of laterality of the responses (number of left and right ear responses),
   
2. the response laterality calculated into a "laterality index", and
   
3. responses rescored according to whether the repeated syllable was selected or not, and then calculated into a "priming index".

In light of the following research, I find the third of these approaches to be the most effective in communicating the priming effect.

Paper on crossmodal primed dichotic listening

This was the first paper in my PhD. Two experiments presented a single prime syllable (the first experiment presented it as sound, the second as text on screen), followed by a dichotic (one in each ear) syllable pair, and asked participants which syllable they heard from the dichotic pair. The results from both experiments showed that participants tended to report the syllable that had been repeated from the prime. In accounting for the results, we said that the selection between the dichotic syllables is a demanding task, and to facilitate the selection, participants inhibit the prime syllable. The inhibition of the syllable is retained at the time of the selection process, and creates a bias for the response. It's interesting that the priming was effective also when it was crossmodal (prime as text, dichotic syllables as sound), from which we can make assumptions about the cognitive level of the mechanism.

Sætrevik & Hugdahl (2007b) Priming inhibits the right ear advantage in dichotic listening - Implications for auditory laterality - Neuropsychologia

I initially intended this as a simple pilot study that should give a positive priming effect, and was quite surprised by the negative priming effect found. This required me to rethink the theoretical model, and consequently changed the form of my PhD project.

This first paper reported the results in terms of laterality of the response (whether the stimulus from the left or right ear was reported), as was common in our research community. I later abandoned this approach, as the priming effect appears to be symmetrical for both ears (although it acts on the background bias of the "right ear advantage"), and instead reported whether or not the repeated syllable was selected or not.

I have not since followed up on the crossmodality of the priming effect.

Master thesis on implicit learning

After much ado my master thesis was published in Learning and Instruction in 2006. The article looks at the phenomenon of implicit learning. It has often been argued based on findings of implicit learning in a lab environment that the approach should be assumed in the educational system. We wanted to test this, and performed implicit learning experiments in a school setting. We found evidence of implicit learning, but found more traditional, explicit teaching to be more efficient.

Sætrevik, Reber & Sannum, 2006 The Utility of Implicit Learning in the Teaching of Rules