The influence of task-irrelevant Navon stimuli on the time-course of visual attention and reaching movements

The aim of this thesis is to examine the time-course of task-irrelevant interference effects in Navon letters. In Navon stimuli, a large letter is composed of small letters and results show that participants are generally faster when the letters are compatible. In the present work, instead of responding to letter identity, participants were required to respond to the luminance of the stimuli. This luminance discrimination task was implemented both when attention was directed to the global and when it was directed to the local level. In the global level task (chapter 2), participants were asked to respond to the luminance of a Navon letter. In the local level task (chapters 3 and 4), task-irrelevance was manipulated by asking participants to respond to the luminance of a dot that was embedded in one of the local letters. Time-course of responding was manipulated by using different luminance contrasts in different experiments. The results showed that participants responded faster when the global and local letter matched. Time-course seemed to be less influential as previously predicted (chapter 5). Finally, task-irrelevant interference effects on the local level were investigated by using a choice-reaching task (chapter 6). No interference effects occurred, neither for initiation latency nor for maximum deviation of the movement trajectory. In conclusion, the findings of this thesis suggest that in a reaction-time task, task-irrelevant interference effects in Navon letters can occur. This seems to be independent of the level of attentional focus

Low prevalence search for cancers in mammograms : evidence using laboratory experiments and computer aided detection

People miss a large proportion of targets when they only appear rarely. This Low Prevalence (LP) Effect could lead to serious consequences if it occurred in the real world task of searching for cancers in mammograms. Using a novel mammogram search task, we asked participants to search for a pre-specified cancer (Experiments 1-2) or a range of masses (Experiments 3-5) under high or low prevalence conditions. Experiment 1 showed that an LP Effect occurred using these stimuli. Experiment 2 tested an over-reliance hypothesis and showed that the use of Computer Aided Detection (CAD) led to fewer missed cancers with a valid CAD prompt yet, a large proportion of cancers were missed when CAD was incorrect. Experiment 3 - 5 showed that false alarms also increased when searching for a range of masses and that CAD reduced miss errors when it correctly cued the target but increased miss errors and false alarms when it did not. Furthermore, when a mass fell outside the CAD prompt it was more likely to be misidentified. No LP Effect was observed with the addition of CAD when people were asked to search for a range of targets. Theories and implications for mammogram search are discussed

We don't know what you did last summer. On the importance of transparent reporting of reaction time data pre-processing

In behavioral, cognitive, and social sciences, reaction time measures are an important source of information. However, analyses on reaction time data are affected by researchers' analytical choices and the order in which these choices are applied. The results of a systematic literature review, presented in this paper, revealed that the justification for and order in which analytical choices are conducted are rarely reported, leading to difficulty in reproducing results and interpreting mixed findings. To address this methodological shortcoming, we created a checklist on reporting reaction time pre-processing to make these decisions more explicit, improve transparency, and thus, promote best practices within the field. The importance of the pre-processing checklist was additionally supported by an expert consensus survey and a multiverse analysis. Consequently, we appeal for maximal transparency on all methods applied and offer a checklist to improve replicability and reproducibility of studies that use reaction time measures

Towards a Better Understanding and Control of Factors Affecting the Physical Quality of Fish Feed

As aquaculture expands, the volume of fish feed produced and transported must also increase. Therefore a better understanding and increased control of the factors that influence the physical quality of feed pellets is required. To achieve this goal, reliable methods measuring the physical quality of feed are needed. The Holmen pellet tester (NHP 100) could be adapted for this purpose, but the special characteristics of fish feed require particular care during testing. The first study showed that when the temperature and operating pressure are maintained at a standardized level, the Holmen pellet tester is a valuable tool for assessing the physical quality of fish feed providing additional information on the quality of feed pellets compared to other durability tests. In the second study, the effect of different levels of sunflower meal, starch and moisture on the stability of physical quality of feed during storage was investigated. After three weeks of storage, the durability of the diet with the elevated levels of all the variables has not changed significantly, while the others showed significant durability decrease. The potential reason for this situation can be a relationship between morphological structure and oil migration in the pellet, which can be restrained by changing diet composition. The oxidation was ruled out as a possible cause of this phenomenon. The third study investigated the effect of the composition of the feed, and the mode of handling, on the mechanical stability of both fresh and aged feed pellets. Intensive handling significantly decreased the durability of fresh pellets; however this decrease in durability was lessened by increasing the moisture content of the feed. In aged pellets, after three weeks of storage, the decrease in durability was more prominent for the feed handled intensively than for the feed handled gently. In the fourth study, the possibility of improving the physical quality of fish feed using protein crosslinking enzyme, transglutaminase, was tested. It was concluded that the transglutaminase treatment, when used at the appropriate dose and under the correct processing conditions, can improve the physical quality of feed pellets. The most important outcome of this work is the increased knowledge about the parameters that cause aging and the identification of tools to control this phenomenon. It also proved that in-line enzymatical modification of feed ingredients is possible and should be investigated further

Standardized method for the Holmen pellet tester (NHP100) as a tool for evaluating the physical quality of fish feed

The fish feed production industry requires reliable methods measuring the physical quality of feed before it is being released to the customer. The Holmen pellet tester (NHP 100) could be adapted for this purpose, but the special characteristics of fish feed require particular care during testing. The aim of the study was to determine the standardized conditions for using the Holmen tester as a tool measuring the durability of fish feed. Screening tests were performed on commercial fish feed samples to assess the effects of temperature, pressure and cleaning the instrument between runs. The operating pressure was found to be the most important factor that can influence the results. The temperature of the operating air can also alter the results; increased temperatures can cause oil to melt and leak from the pellets. Cleaning the instrument between analyses can also affect the results. This study shows that when these factors are maintained at a standardized level, the Holmen pellet tester is a valuable tool for assessing the physical quality of fish feed giving additional information on the quality of feed pellets compared to other durability tests like DORIS

The addition of transglutaminase improves the physical quality of extruded fish feed

The possibility of improving the physical quality of extruded fish feed using transglutaminase (TGase) treatment at different stages of the production process was investigated. The addition of TGase to the raw material mix and processing under high and medium moisture conditions significantly increased (p > 0.05) the durability, hardness and elasticity of fish feed pellets. However, the water stability of feeds was only improved when the TGase was applied in the vacuum coater; when it was mixed with the dry raw materials, the water stability of the product decreased. By further optimization of the enzyme dose when added to the vacuum coater, an increase in pellet durability was observed at enzyme dosages between 2.5 and 5 g kg(-1). Application of TGase in the coating step allowed an 87.5 % decrease in the dose of enzyme in feed produced under high moisture conditions. TGase treatment improves the physical quality of extruded fish feed, and the importance of optimization of enzyme dosage and processing conditions was demonstrated