A color-digit Stroop task shows numerical influence on numerosity processing.

The numerical Stroop task involves presenting participants with two digits that differ in physical size and numerical value and asking them to report which digit had the larger size or value while ignoring the other dimension. Previous studies show that participants have difficulty ignoring the irrelevant dimension and thus have implications on the automaticity of numerical processing. The present study investigates the automatic influence of numerical value on numerosity processing in a novel Stroop-like task. In two experiments, participants were presented with digits made of colored stripes and asked to identify the number of different colors. In both experiments, interference and facilitation effects were found, supporting the automaticity of symbolic number processing and its influence on numerosity processing. These findings expand upon previous research on numerical as well as counting Stroop tasks, and have potential implications for studying interference and basic numerical processing in children and clinical populations.

Using facial expressions instead of response keys in the implicit association test.

Previous research found that when people are instructed to smile toward liked objects and show negative facial expressions toward disliked objects, their facial response is faster and more intense than when they are required to smile toward disliked objects and express negative facial response toward liked objects. The present research tested a technologically innovative indirect evaluation measure that was based on that finding. Participants completed an implicit association test (IAT)-a common indirect measure of evaluation, responding with their emotional facial expressions, rather than by pressing response keys. In two web studies, using emotional facial expression detection through a webcam, we found that the Facial Response IAT (FR-IAT) is a reliable and valid measure of evaluations, comparable to the keyboard IAT. Because facial responses provide more information than key responses, pursuing future improvements of the FR-IAT's methodology, software, and data analysis is a promising direction for enhancing the quality of indirect evaluation measurement. The same methodology and technology may also enhance other indirect measures of evaluation and cognitive tests related to emotion and judgment.

The contribution of temporal analysis of pupillometry measurements to cognitive research.

Reaction time (RT) is one of the most frequently used measures to detect cognitive processes. When tasks require more cognitive processes/resources, reaction is slower. However, RTs may provide only restricted information regarding the temporal characteristics of cognitive processes. Pupils respond reflexively to light but also to cognitive activation. The more cognitive resources a task requires, the more the pupil dilates. However, despite being able to use temporal changes in pupil size (advanced devices measure changes in pupil diameter with sampling rates of above 1000 samples per second), most past studies using pupil dilation have not investigated temporal changes in pupil response. In the current paper, we discuss the advantage of the temporal approach to analyze pupil changes compared to a more traditional perspective, specifically, singular value methods such as mean value and peak amplitude value. Using data from two recent studies conducted in our laboratory, we demonstrate the differences in findings arising from the various analyses. In particular, we focus on the advantage of temporal analysis in detecting hidden effects, investigating temporal characterizations of the effects, and validating the experimental manipulation.

Neutral stimuli and pupillometric task conflict.

It has been suggested that the interference in the Stroop task arises due to both information conflict (color vs. word meaning) and task conflict (respond to the color vs. read the word). Interestingly, the task conflict (faster responses in the congruent condition compared to the neutral condition) is influenced by the readability of the stimulus. However, behavioral results indicate the influence of the contribution of readability to the task conflict appears only when vocal responses are required. We conducted a Stroop experiment with four readability levels of neutrals. Participants were required to respond manually, and both their response times and pupil dilation were measured. Our results showed the slowest responses for incongruent trials and the fastest responses for congruent trials. However, no differences in responses were found between the readability levels of the neutrals. In contrast, pupil dilation showed the largest dilation in the incongruent trials and smallest dilation in the neutral trials. In addition, the differences between congruent and neutral trials were influenced by the readability of the stimulus. Specifically, unreadable neutral stimuli showed meaningful differences early on, which also remained for longer time compared with readable neutral stimuli. These results are important and can help in specifying new requirements regarding the theory and modeling of the Stroop task; in particular, studies that want to control the neutrality of their neutral trials should take the readability into account.

Pupillometric contributions to deciphering Stroop conflicts.

The Stroop task gives rise to two major conflicts: the task conflict (respond to the color vs. read the word) and the information conflict that can result from the stimulus-response compatibility (SRC; difference between two responses) or from the stimulus-stimulus compatibility (SSC; difference between the two contradictive pieces of information). We conducted a two-to-one Stroop experiment (i.e., two colors are mapped to one response key) and measured reaction time and pupil dilation. The results showed clear evidence for informational conflict composed of both the SRC and SSC. In addition, pupil indications for task conflict appeared earlier than indications for both the SSC and the SRC, in line with the theory regarding task conflict.

CHAP: Open-source software for processing and analyzing pupillometry data.

Pupil dilation is an effective indicator of cognitive and affective processes. Although several eyetracker systems on the market can provide effective solutions for pupil dilation measurement, there is a lack of tools for processing and analyzing the data provided by these systems. For this reason, we developed CHAP: open-source software written in MATLAB. This software provides a user-friendly graphical user interface for processing and analyzing pupillometry data. Our software creates uniform conventions for the preprocessing and analysis of pupillometry data and provides a quick and easy-to-use tool for researchers interested in pupillometry. To download CHAP or join our mailing list, please visit CHAP's website: http://in.bgu.ac.il/en/Labs/CNL/chap .

A novel blink detection method based on pupillometry noise.

Pupillometry (or the measurement of pupil size) is commonly used as an index of cognitive load and arousal. Pupil size data are recorded using eyetracking devices that provide an output containing pupil size at various points in time. During blinks the eyetracking device loses track of the pupil, resulting in missing values in the output file. The missing-sample time window is preceded and followed by a sharp change in the recorded pupil size, due to the opening and closing of the eyelids. This eyelid signal can create artificial effects if it is not removed from the data. Thus, accurate detection of the onset and the offset of blinks is necessary for pupil size analysis. Although there are several approaches to detecting and removing blinks from the data, most of these approaches do not remove the eyelid signal or can result in a relatively large amount of data loss. The present work suggests a novel blink detection algorithm based on the fluctuations that characterize pupil data. These fluctuations ("noise") result from measurement error produced by the eyetracker device. Our algorithm finds the onset and offset of the blinks on the basis of this fluctuation pattern and its distinctiveness from the eyelid signal. By comparing our algorithm to three other common blink detection methods and to results from two independent human raters, we demonstrate the effectiveness of our algorithm in detecting blink onset and offset. The algorithm's code and example files for processing multiple eye blinks are freely available for download ( https://osf.io/jyz43 ).

Resting Stroop task: Evidence of task conflict in trials with no required response.

In the typical Stroop task, participants are presented with color words written in different ink colors and are asked to respond to their color. It has been suggested that the Stroop task consists of two main conflicts: information conflict (color vs. word naming) and task conflict (respond to color vs. read the word). In the current study, we developed a novel task that includes both Response trials (i.e., trials in which a response is required) and Rest trials (i.e., trials in which no response is required or available) and investigated the existence of both information and task conflicts in Rest trials. We found evidence for task conflict in Response and also in Rest trials, while evidence for information conflict was only observed in Response trials. These results are in line with a model of task conflict that occurs independently of and prior to information conflict in the Stroop task.

Insights from Eye Blinks into the Cognitive Processes Involved in Visual Word Recognition.

Behavioral differences in speed and accuracy between reading familiar and unfamiliar words are well-established in the empirical literature. However, these standard measures of skill proficiency are limited in their ability to capture the moment-to-moment processing involved in visual word recognition. In the present study, the effect of word familiarity was initially investigated using an eye blink rate among adults and children. The probability of eye blinking was higher for familiar (real) words than for unfamiliar (pseudo)words. This counterintuitive pattern of results suggests that the processing of unfamiliar (pseudo)words is more demanding and perhaps less rewarding than the processing of familiar (real) words, as previously observed in both behavioral and pupillometry data. Our findings suggest that the measurement of eye blinks might shed new light on the cognitive processes involved in visual word recognition and other domains of human cognition.

Evidence for Two Types of Task Conflict in a Color-Digit Stroop Task.

In the present study, we conducted a Stroop-like task in which the participants were required to decide whether the presented stimulus, which could be either a colored digit or a colored rectangle, consisted of more or less than five colors. Like other Stroop-like tasks, the stimuli could be congruent (the stimulus was a digit that was equal to the presented number of colors), incongruent (the stimulus was a digit that was different than the presented number of colors), or neutral (a colored rectangle). We utilized a two-to-one response setting so that in some incongruent trials the digit and the number of colors would elicit the same response (e.g., the digit 3 containing two colors; both are smaller than 5), while in some incongruent trials, the digit and the number of colors would elicit different responses (e.g., the digit 3 containing 6 colors). This enabled us to measure both conflicts arising from stimulus-stimulus and stimulus-response compatibilities. Our results indicated the existence of stimulus-stimulus compatibility (SSC), stimulus-response compatibility (SRC), and task conflict. Interestingly, these effects were in interaction with the number of colors, so that in small numbers, SSC and SRC were found, and in large numbers, SRC and task conflict were found. Moreover, the results suggest that our task includes two types of task conflict that are raised due to three different tasks: processing the meaning of the digit vs. estimating the number of colors and counting the number of colors vs. estimating the number of colors.