PhD Thesis by Jonas Olsen Dall: An Investigation Into the Perceptual Influence of Prior Information in the Human Cognitive System
Classic studies in psychology have shown that attention span and memory capacity is highly limited. These capacities further decrease if the to be remembered stimuli are something unfamiliar. The aim of this thesis is therefore to study the mechanics behind this change in capacity.
Study 1 had the dual purpose of both studying these phenomena and showing that stimuli specific expertise was possible to build in adulthood. My co-authors and I did this by extending a previous study (Sørensen & Kyllingsbæk, 2012) from looking at Visual Short-Term Memory (VSTM) changes in early life related Latin letter expertise to late-in-life acquired Japanese hiragana expertise. We did this by studying the Visual Short-Term Memory capacity (K) for the comparisons (Japanese hiragana) and two control stimuli (Pictures and Latin letters) in participants at three different levels of stimuli specific expertise: Danish university students with no Japanese expertise (Novice), Danish students studying Japanese at the University (Trained), and Native Japanese University students (Expert). We found that there were no significant differences between the groups in the two control stimuli. There was, however, an expertise related influence in the hiragana condition (Novice < Trained < Expert). Furthermore, despite the more visually complex Japanese hiragana, there was no significant difference in the native languages. Furthermore, no differences were found for Latin for Novice and Trained compared to hiragana for the Japanese, despite the fact that Japanese hiragana is visually more complex.
Study 2 studied the relationship between this apparent visual complexity and stimuli specific expertise. This was achieved by using Chinese characters as they have an approximation for both stroke count as visual complexity and frequency of use as stimuli specific expertise. Stimuli were divided into four conditions based on stroke count and frequency of use: High-Stroke High-Frequency, High-Stroke Low- Frequency, Low-Stroke High-Frequency, and Low-Stroke Low-Frequency. The study found no significant influence of stroke count while finding that frequency of use influenced both K and processing speed (C) without influencing threshold for perception (t0). This raises the question of whether K and C have an effect on stimuli specific expertise or if the differences are due to a stronger mental resolution of stimuli stored in VSTM.
This question of stimuli specific expertise and mental resolution were studied in study 3 by using continuous categories. Stimuli were divided into two conditions: colour as continuous categories and Latin letters as a control condition. Participants used a colour wheel to report the stimuli on the colour trial. The precision of these answers were based on the distance between answers on the colour wheel to what they were shown. Expertise was modulated by dividing participants into two groups: Danish psychology students with no training in colour, design, or other visual arts (Novice) as well as Danish students at School of Visual Arts at the Royal Danish Academy of Fine Arts (Expert). We did not find any difference between the two groups in either colour precision, C, or t0. However, colour experts showed a significantly higher K for colours than Novices.
The studies comprising my thesis may suggest that stimuli specific expertise can be gained late in life and increases both memory capacity and processing speed. These changes can furthermore not be explained by increases in mental resolution of the stored items but instead as increases in stimuli specific memory capacity.