The Hawthorne Effect in Eye-blinking: Awareness that One's Blinks are Being Counted Alters Blink Behavior

The time-course of visual scanning behaviour of paramedicine students upon arrival at a simulated emergency call

BACKGROUND

Limited knowledge exists regarding how paramedics acquire an understanding of the scene they encounter upon arrival, despite their need to quickly gather information for effective clinical decision-making. This study examined visual scanning behaviour during the early stages of simulated emergency calls.

METHODS

Eye movements of 10 paramedicine students were recorded during simulated calls conducted in both a high-fidelity classroom setting and a full sensory immersion setting.

RESULTS

Students focused on similar areas in both settings, with most time spent looking at the patient rather than distractors such as room features or other people. Analysis of gaze behaviour across the first five minutes revealed a more nuanced pattern: attention initially gravitated towards distractors but decreased as students became familiar with their surroundings and focused on the task at hand. This pattern was consistent across both simulation settings, indicating that information-seeking strategies may be independent of scene complexity.

CONCLUSIONS

Expertise relies on the ability to differentiate between relevant and irrelevant information. Given the unpredictable nature of their work, paramedics must continuously adapt their understanding of a scene from the moment they enter it. Understanding how this skill develops may help identify expert strategies to inform training of novice paramedics.

Rapid Voluntary Blinking as a Clinical Marker of Parkinson's Disease

Reduced spontaneous blinking is a recognized Parkinson's disease (PD) feature. In contrast, voluntary blinking has been less studied and might serve as a measurable marker of facial bradykinesia. We tested 31 PD patients and 31 controls. Participants were filmed during conversation and a rapid blinking task. Both tasks were videorecorded to count the number of blinks per second. PD patients had lower blink rates. Rapid blinking accurately discriminated between groups with 77% sensitivity and 71% specificity. To conclude, rapid blinking may be a simple and quantifiable task of facial bradykinesia.

Defining and evaluating the Hawthorne effect in primary care, a systematic review and meta-analysis

In 2015, we conducted a randomized controlled trial (RCT) in primary care to evaluate if posters and pamphlets dispensed in general practice waiting rooms enhanced vaccination uptake for seasonal influenza. Unexpectedly, vaccination uptake rose in both arms of the RCT whereas public health data indicated a decrease. We wondered if the design of the trial had led to a Hawthorne effect (HE). Searching the literature, we noticed that the definition of the HE was unclear if stated. Our objectives were to refine a definition of the HE for primary care, to evaluate its size, and to draw consequences for primary care research. We designed a Preferred Reporting Items for Systematic reviews and Meta-Analyses review and meta-analysis between January 2012 and March 2022. We included original reports defining the HE and reports measuring it without setting limitations. Definitions of the HE were collected and summarized. Main published outcomes were extracted and measures were analyzed to evaluate odds ratios (ORs) in primary care. The search led to 180 records, reduced on review to 74 for definition and 15 for quantification. Our definition of HE is "an aware or unconscious complex behavior change in a study environment, related to the complex interaction of four biases affecting the study subjects and investigators: selection bias, commitment and congruence bias, conformity and social desirability bias and observation and measurement bias." Its size varies in time and depends on the education and professional position of the investigators and subjects, the study environment, and the outcome. There are overlap areas between the HE, placebo effect, and regression to the mean. In binary outcomes, the overall OR of the HE computed in primary care was 1.41 (95% CI: [1.13; 1.75]; I 2 = 97%), but the significance of the HE disappears in well-designed studies. We conclude that the HE results from a complex system of interacting phenomena and appears to some degree in all experimental research, but its size can considerably be reduced by refining study designs.

Ocular surface cooling rate associated with tear film characteristics and the maximum interblink period

The surface of the human eye is covered with a protective tear film that refreshes with each blink. Natural blinking occurs involuntarily, but one can also voluntarily blink or refrain from blinking. The maximum time one can refrain from blinking until the onset of discomfort is the maximum interblink period (MIBP). During the interblink period the tear film evaporates and thins from the ocular surface. Infrared thermography provides a non-invasive measure of the ocular surface temperature (OST). Due to evaporation, ocular surface cooling (OSC) generally occurs when the eyes are open and exposed to the environment. The purpose of our study was to investigate the effect of OSC rate on the MIBP, and to investigate the association of the MIBP with tear film characteristics in subjects who do and do not exhibit OSC. The MIBP was measured simultaneously with OST over time. Non-invasive tear breakup time, tear meniscus height, tear lipid layer thickness, and Schirmer I test strip wetted lengths were measured on a day prior to the thermography visit. Subjects were divided into cooling and non-cooling groups based on OSC rate, and demographic and tear film characteristics were tested for inter-group differences. A faster OSC rate was associated with an exponentially shorter duration of the MIBP overall and within the cooling group alone. Faster non-invasive tear breakup time was significantly associated with a shorter MIBP in both groups. These results suggest that tear film evaporation initiates a pathway that results in the onset of ocular discomfort and the stimulus to blinking. The presence of a subset of subjects with no or minimal OSC who nevertheless have a short MIBP indicates that evaporative cooling is not the only mechanism responsible for the onset of ocular discomfort.