A common conceptualization of signal detection theory (SDT) holds that if the effect of an experimental manipulation is truly perceptual, then it will necessarily be reflected in a change in d' rather than a change in the measure of response bias. Thus, if an experimental manipulation affects the measure of bias, but not d', then it is safe to conclude that the manipulation in question did not affect perception but instead affected the placement of the internal decision criterion. However, the opposite may be true: an effect on perception may affect measured bias while having no effect on d'. To illustrate this point, we expound how signal detection measures are calculated and show how all biases-including perceptual biases-can exert their effects on the criterion measure rather than on d'. While d' can provide evidence for a perceptual effect, an effect solely on the criterion measure can also arise from a perceptual effect. We further support this conclusion using simulations to demonstrate that the Müller-Lyer illusion, which is a classic visual illusion that creates a powerful perceptual effect on the apparent length of a line, influences the criterion measure without influencing d'. For discrimination experiments, SDT is effective at discriminating between sensitivity and bias but cannot by itself determine the underlying source of the bias, be it perceptual or response based.

Through training, skilled parkour athletes (traceurs) overcome everyday obstacles, such as walls, that are typically insurmountable. Traceurs and untrained novices estimated the height of walls and reported their anticipated ability to climb the wall. The traceurs perceived the walls as shorter than did novices. This result suggests that perception is scaled by the perceiver's anticipated ability to act, and is consistent with the action-specific account of perception.

During a pandemic, news media play a crucial role in communicating public health and policy information. Traditional newspaper coverage is important amidst increasing disinformation, yet uncertainties make covering health risks and efforts to limit transmission difficult. This study assesses print and online newspaper coverage of the coronavirus disease COVID-19 for March 2020, when the global pandemic was declared, through August 2020 in three countries: Canada (with the lowest per-capita case and death rates during the study timeframe), the United Kingdom (with a pronounced early spike), and the United States (with persistently high rates). Tools previously validated for pandemic-related news records allow measurement of multiple indicators of scientific quality (i.e., reporting that reflects the state of scientific knowledge) and of sensationalism (i.e., strategies rendering news as more extraordinary than it really is). COVID-19 reporting had moderate scientific quality and low sensationalism across 1331 sampled articles in twelve newspapers spanning the political spectrums of the three countries. Newspapers oriented towards the populist-right had the lowest scientific quality in reporting, combined with very low sensationalism in some cases. Against a backdrop of world-leading disease rates, U.S. newspapers on the political left had more exposing coverage, e.g., focused on policy failures or misinformation, and more warning coverage, e.g., focused on the risks of the disease, compared to U.S. newspapers on the political right. Despite the generally assumed benefits of low sensationalism, pandemic-related coverage with low scientific quality that also failed to alert readers to public-health risks, misinformation, or policy failures may have exacerbated the public-health effects of the disease. Such complexities will likely remain central for both pandemic news media reporting and public-health strategies reliant upon it.

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According to the action-specific account of perception, perceivers see the environment relative to their ability to perform the intended action. For example, in a modified version of the computer game Pong, balls that were easier to block looked to be moving slower than balls that were more difficult to block (Witt & Sugovic, 2010). It is unknown, however, if perception can be influenced by another person's abilities. In the current experiment, we examined whether another person's ability to block a ball influenced the observer's perception of ball speed. Participants played and observed others play the modified version of Pong where the task was to successfully block the ball with paddles that varied in size, and both the actor and observer estimated the speed of the ball. The results showed that both judged the ball to be moving faster when it was harder to block. However, the same effect of difficulty on speed estimates was not found when observers watched a computer play, suggesting the effect is specific to people and not to the task. These studies suggest that the environment can be perceived relative to another person's abilities.