p-value

p-value for the layman

Statistics can often feel like a labyrinth of complex numbers and jargon. In the world of statistics, p-values are your compass. While the concept may seem a bit abstract at first, p-values are like a traffic light for your scientific discoveries, guiding you to proceed with caution or giving you the green light to embrace a new understanding of the world.

What is a p-value?

At its core, a p-value is a number that helps us determine the significance of an observation or result in statistical analysis. Imagine you've conducted an experiment or a survey, and you want to know if your findings are meaningful or just a result of chance. The p-value is your guide.

The Role of Probability

To grasp p-values, you need to understand the concept of probability. Think of it as a measure of how likely something is to happen. In statistics, we often want to know the probability of observing certain data if there's no real effect or difference. This is where p-values come into play.

Hypotheses: The Foundation

In any scientific study, you start with two hypotheses: the null hypothesis (H0) and the alternative hypothesis (H1). The null hypothesis represents the idea that there's no significant effect or difference, while the alternative hypothesis suggests the opposite – that there is a significant effect or difference.


The Experiment and the Data

You gather your data, conduct your analysis, and calculate a test statistic, which quantifies the difference between your observed data and what you would expect under the null hypothesis. This test statistic follows a particular distribution, like the normal distribution for many common statistical tests.

The P-Value's Revelation

Here's the moment of truth: the p-value tells you the probability of obtaining a test statistic as extreme as, or more extreme than, the one you calculated if the null hypothesis is true. In simpler terms, it answers the question: "How likely is it that my observed results are just due to random chance?"

Interpreting P-Values

Now, the key interpretation comes into play. If your p-value is small, typically less than 0.05 (but it can vary depending on the field), it suggests that your observed results are unlikely to have occurred by chance alone. This is your green light to reject the null hypothesis and accept that you've found something significant.

Conversely, if your p-value is large (greater than 0.05), it indicates that your observed results are quite likely to be explained by random chance, and you should stick with the null hypothesis.

It's Not Absolute Proof

One crucial thing to understand is that p-values don't provide absolute proof or disproof. They offer a level of evidence, but they can't tell you the size of an effect or whether it's practically meaningful. They merely guide you in determining if your results are statistically significant.

Simultaneity Window

[Concepts in Sensorimotor Research]

Simultaneity Window (SW) refers to a temporal window within which the brain perceives stimuli from different sensory modalities as occurring simultaneously. It represents the temporal range over which the brain integrates sensory inputs from different modalities into a coherent percept.

If stimuli from different modalities fall within the SW, they are likely to be perceptually integrated, whereas if they fall outside the SW, they may be perceived as separate events.

Commonly used research tasks to measure SW

• Temporal Order Judgment (TOJ): participants are presented with 2 stimuli, one in each sensory modality (e.g., a flash of light and a beep), and they have to determine the order in which the stimuli occurred.
• Simultaneity Judgment (SJ): Participants are presented with 2 stimuli, from different modalities, and they have to judge whether the stimuli were perceived as simultaneous or not.
• Temporal Alignment Task: Participants are presented with a stimulus in one modality and have to adjust the timing of a stimulus in the other modality until it is perceived as synchronous with the first stimulus. This helps in determining the temporal window of integration.
• Temporal Recalibration Task: Participants are exposed to a consistent asynchrony between stimuli from different modalities over a period of time. Following this exposure, their perception of simultaneity is tested to see if it has been recalibrated.

The perception of simultaneity can vary across individuals and is influenced by various factors such as attention, age, disability, the specific sensory modalities involved, and distance of stimuli (as determined by, say the PPS).

Psychophysics and Autism

The field of psychophysics explores how humans perceive and interpret sensory information, including vision, hearing, touch, taste, and smell. It investigates how changes in physical stimuli result in changes in perception, allowing researchers to measure and quantify the relationships between physical stimuli and perceptual experiences.

Psychophysical experiments often involve participants making judgments or providing responses to stimuli under controlled conditions. These experiments use psychophysical techniques to measure and analyze perceptual thresholds, discrimination abilities, response biases, and other aspects of sensory perception.

Some common psychophysical methods and measures include:

• Threshold determination: Identifying the minimum or maximum level of a stimulus that can be detected or discriminated.
• Scaling: Estimating subjective perceptions using rating scales or magnitude estimation.
• Difference thresholds: Assessing the smallest detectable difference between two stimuli.
• Response time measures: Examining the speed of processing or decision-making in response to stimuli.

Psychophysics has contributed to our understanding of sensory perception, including concepts such as Weber's Law, Stevens' Power Law, and Fechner's Law. It has applications in various fields, such as vision science, auditory perception, psychopharmacology, and the study of human factors in design and technology.

Use of Psychophysics in  Autism Research

• Sensory processing differences at various levels, such as visual, auditory, and tactile domains. Researchers have utilized psychophysical methods to measure thresholds, discrimination abilities, and response biases related to sensory perception. This helps in identifying specific sensory sensitivities, hypo- or hyper responsiveness, and atypical processing patterns in individuals with autism
• Perceptual integration and binding of perceptual features, such as color, motion, or shape, in autistics. By examining how autistics perceive and integrate different sensory information, researchers gain insights into potential difficulties in integrating and perceiving coherent perceptual representations.
• Face and emotion perception studies investigate perceptual thresholds, discrimination abilities, and biases related to facial features, expressions, and emotional cues. They can provide insights into the specific challenges  in perceiving and interpreting social cues.
• Multisensory processing: Psychophysics has been utilized to explore how autistics integrate information from multiple sensory modalities. By measuring sensory integration and cross-modal processing abilities, researchers gain a better understanding of how individuals combine information from different sensory channels, which can contribute to their overall perceptual experiences.

Oddball Paradigms

 [Concepts in Sensorimotor Research]

Oddball trials, also known as oddball tasks or oddball paradigms, are a type of research experimental design. In oddball trials, a sequence of stimuli is presented to participants, and their task is to detect and respond to specific target stimuli embedded within a stream of more frequent, standard stimuli. The oddball paradigm has been widely used in autism research to investigate sensory processing differences, attentional issues, and cognitive control.

The oddball paradigm typically consists of two types of stimuli:

• Standard Stimuli: These are the most common stimuli presented in the sequence and serve as the baseline / control stimuli, occurring with higher frequency. Participants are generally instructed to ignore standard stimuli and withhold any response to them
• Target Stimuli: These are the less frequent or "oddball" stimuli that differ in some way from the standard stimuli. Participants are instructed to actively detect and respond to these target stimuli. The target stimuli can be defined by various characteristics, such as a different color, shape, sound, or any other perceptual feature.

The purpose of oddball trials is to investigate how the brain processes and detects rare or deviant stimuli amidst a background of more common stimuli. By manipulating the frequency and characteristics of the target and standard stimuli, researchers can examine various aspects of cognitive processing, including

• Attention: how participants allocate and sustain their attention to detect infrequent target stimuli. It allows researchers to explore the mechanisms of selective attention, attentional capture, and the ability to filter out irrelevant information.
• Perception & perceptual processing: how the brain discriminates between different stimuli; how the brain detects and discriminates deviant stimuli based on sensory features, and how it forms representations and expectations about the environment
• Memory and Cognitive Control: Participants may be required to remember the occurrence or characteristics of the target stimuli and maintain this information for subsequent recall or recognition. Also sheds light on cognitive control processes, such as response inhibition and response selection when distinguishing between standard and target stimuli.

During an oddball task, researchers typically measure various physiological and behavioral responses, such as reaction times, accuracy rates, ERPs (via EEG) or fMRI (to examine neural activity patterns).

Review v Meta Analysis

I continue to learn....as I navigate grad school

Review vs Meta-Analysis

A review paper /literature review, provides a comprehensive overview and evaluation of existing research on a particular topic. It involves gathering information from multiple sources, such as research articles, books, and other relevant publications, and synthesizing the findings to summarize the current state of knowledge on the topic. Review papers typically do not involve statistical analysis or original data collection.

A meta-analysis is a specific type of research synthesis that involves combining and analyzing quantitative data from multiple studies to generate more robust conclusions. Researchers identify relevant studies, extract relevant data from each study, and statistically analyze the combined data to derive overall effect sizes or estimates of the relationship between variables. Meta-analyses often include a systematic review of the literature as a first step to identify relevant studies for inclusion.

Mental Time Travel

The concept of mental time travel (MTT) refers to the ability of individuals to mentally project themselves backward in time to relive or remember past events, as well as forward in time to imagine or anticipate future events. It is a cognitive process that allows us to mentally simulate and navigate through temporal experiences beyond the present moment.

The MTT task is a neuroscience measure designed to assess an individual's capacity for mental time travel. It typically involves presenting participants with a series of event cues and asking them to generate specific events from their own personal past or future that are related to each cue. For example, participants may be shown cue words such as "graduation" or "vacation" and then asked to recall a specific past event or imagine a specific future event related to each cue.

In this task, the individual's present moment serves as a reference point from which they situate and retrieve personal versus general events. Personal events refer to specific episodic memories from the individual's own life, such as a birthday party or a family trip, while general events are more abstract and can be shared by multiple individuals, such as historical events or holidays.

The MTT task taps into several cognitive processes and neural mechanisms associated with mental time travel. It requires the retrieval of specific episodic memories or the construction of plausible future scenarios. The task engages memory processes, including recall and recognition, as well as imagination and prospective thinking.

Neuroimaging studies have shown that the neural substrates underlying MTT involve a network of brain regions.

• PFC:  cognitive control and executive function required for retrieving and manipulating temporal information. 
• Hippocampus and MTL: formation and retrieval of episodic memories

The MTT task has been used in research to investigate individual differences in the capacity for mental time travel and how it relates to various cognitive processes, such as autobiographical memory, imagination, planning, and self-projection. It has also been employed to examine the effects of aging, neurodegenerative diseases, and psychiatric disorders on mental time travel abilities.

MAST - The Maastricht Acute Stress Test

[concepts in Sensorimotor Research] 

The Maastricht Acute Stress Test (MAST) is a research laboratory procedure that is used to induce stress in research participants. It is used to study the effects of stress on a variety of physiological and psychological processes, including heart rate, blood pressure, cortisol levels, anxiety, and depression. The MAST combines elements from two of the most common experimental paradigms measuring stress, the Trier Social Stress Test (TSST) and the Cold Pressor Test (CPT).

The Test: 
There is a 5-minute preparation phase, during which the participant is seated in a comfortable chair and is given instructions about the task. The participant is then asked to put their right hand into a bowl of ice water for 60-90 seconds. In between each hand immersion trial, the participant is asked to complete a series of mental arithmetic problems. The participant is given negative feedback if they make a mistake or take too long to answer a question.

The test takes approximately 20 minutes to complete. During the procedure, the participant's heart rate, BP, and salivary cortisol levels are measured. The participant is also asked to rate their subjective feelings of stress on a scale of 1 to 10.

Benefits

• It is a simple and easy-to-use procedure.
• It is non-invasive and does not pose any risk to participants.
• It is effective at inducing stress in participants.
• It can be used to measure a variety of stress-related outcomes.

Limitations

• Laboratory-based procedures may not be representative of real-world stress.
• It can be stressful for participants and may not be suitable for everyone. (will autistics even agree to do this?)
• It is not a diagnostic tool and cannot be used to diagnose any medical conditions.

https://www.frontiersin.org/articles/10.3389/fpsyg.2017.00567/full