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When Antoine Arnauld in his Fourth Set of Objections to Descartes’ Meditations expressed the difficulty of accepting the certainty that God exists only because we clearly and distinctly perceive this, with the claim that, what we clearly and distinctly perceive is true only because God exists; he sets the structural problem of Cartesian epistemology, which is also popularly known as the Cartesian Circle. Descartes replied by drawing attention to the difference between clear and distinct perceptions to which one is actually attending and clear and distinct perceptions that one merely remembers having considered in the past. He claims that whereas the former sort of perception is beyond doubt, the latter cannot be trusted until it is established that a non-deceptive God exists. The controversy surrounding the Cartesian Circle has been reduced to the debates concerning the questions of whether Descartes was interested mainly in providing a psychologically stable system of beliefs, or if he wanted to establish that these beliefs correspond to reality. Hence, the underlying question concerning the Cartesian Circle, is whether Descartes is intended to provide a deep challenge to the reliability of human cognition, or he merely wanted to use the skeptical process to direct the reader to clear and distinct perception and then on to the first principles of metaphysics. Whereas there is evidence on both sides of the argument, the present essay will focus specifically on the metaphysics of God.

Individuals with music training in early childhood show enhanced processing of musical sounds, an effect that generalizes to speech processing. However, the conclusions drawn from previous studies are limited due to the possible confounds of predisposition and other factors affecting musicians and nonmusicians. We used a randomized design to test the effects of a laboratory-controlled music intervention on young infants’ neural processing of music and speech. Nine-month-old infants were randomly assigned to music (intervention) or play (control) activities for 12 sessions. The intervention targeted temporal structure learning using triple meter in music (e.g., waltz), which is difficult for infants, and it incorporated key characteristics of typical infant music classes to maximize learning (e.g., multimodal, social, and repetitive experiences). Controls had similar multimodal, social, repetitive play, but without music. Upon completion, infants’ neural processing of temporal structure was tested in both music (tones in triple meter) and speech (foreign syllable structure). Infants’ neural processing was quantified by the mismatch response (MMR) measured with a traditional oddball paradigm using magnetoencephalography (MEG). The intervention group exhibited significantly larger MMRs in response to music temporal structure violations in both auditory and prefrontal cortical regions. Identical results were obtained for temporal structure changes in speech. The intervention thus enhanced temporal structure processing not only in music, but also in speech, at 9 mo of age. We argue that the intervention enhanced infants’ ability to extract temporal structure information and to predict future events in time, a skill affecting both music and speech processing.

Although estimating travel distance is essential to our ability to move through the world, our distance estimates can be inaccurate. These odometric errors occur because people tend to perceive that they have moved further than they had. Many of the studies investigating the perception of travel distance have primarily used forward translational movements, and postulate that perceived travel distance results from integration over distance and is independent of travel speed. Speed effects would imply integration over time as well as space. To examine travel distance perception with different directions and speeds, we used virtual reality (VR) to elicit visually induced self-motion. Participants (n = 15) were physically stationary while being visually “moved” through a virtual corridor, either judging distances by stopping at a previously seen target (Move-To-Target Task) or adjusting a target to the previous movement made (Adjust-Target Task). We measured participants’ perceived travel distance over a range of speeds (1–5 m/s) and distances in four directions (up, down, forward, backward). We show that the simulated speed and direction of motion differentially affect the gain (perceived travel distance / actual travel distance). For the Adjust-Target task, forwards motion was associated with smaller gains than either backward, up, or down motion. For the Move-To-Target task, backward motion was associated with smaller gains than either forward, up or down motion. For both tasks, motion at the slower speed was associated with higher gains than the faster speeds. These results show that transforming visual motion into travel distance differs depending on the speed and direction of optic flow being perceived. We also found that a common model used to study the perception of travel distance was a better fit for the forward direction compared to the others. This implies that the model should be modified for these different non-forward motion directions.

Is there a universal hierarchy of the senses, such that some senses (e.g., vision) are more accessible to consciousness and linguistic description than others (e.g., smell)? The long-standing presumption in Western thought has been that vision and audition are more objective than the other senses, serving as the basis of knowledge and understanding, whereas touch, taste, and smell are crude and of little value. This predicts that humans ought to be better at communicating about sight and hearing than the other senses, and decades of work based on English and related languages certainly suggests this is true. However, how well does this reflect the diversity of languages and communities worldwide? To test whether there is a universal hierarchy of the senses, stimuli from the five basic senses were used to elicit descriptions in 20 diverse languages, including 3 unrelated sign languages. We found that languages differ fundamentally in which sensory domains they linguistically code systematically, and how they do so. The tendency for better coding in some domains can be explained in part by cultural preoccupations. Although languages seem free to elaborate specific sensory domains, some general tendencies emerge: for example, with some exceptions, smell is poorly coded. The surprise is that, despite the gradual phylogenetic accumulation of the senses, and the imbalances in the neural tissue dedicated to them, no single hierarchy of the senses imposes itself upon language.

Perception is influenced by contextual factors that help resolve sensory uncertainty. A well-known phenomenon, the central tendency effect, describes how perceptual estimates gravitate toward the mean of a distribution of stimuli, particularly when sensory input is unreliable. However, in multisensory contexts, it remains unclear whether this effect follows a generalized priority across modalities or might be influenced by task-relevant sensory dominance. We studied spatial and temporal estimation in the auditory and visual modalities, testing whether perceptual estimates are driven by a supra-modal prior or by modality reliability specific to the task, and applied Bayesian modeling to explain the results. Participants first performed baseline sessions using only one modality and then a third session in which the modalities were interleaved. In the interleaved session, we found that the changes in auditory and visual estimates were not towards a supra-modal (generalized) prior, but estimates related to the dominant modality (vision for space, audition for time) were stable, while estimates of the other sensory modality (audition for space, vision for time) were pulled towards the dominant modality’s prior. Bayesian modeling also confirmed that the best-fitting models were those in which priors were modality-specific rather than supra-modal. These results highlight that perceptual estimation favors sensory reliability over a general tendency to regress toward the mean, providing insights into how the brain integrates contextual information across modalities.

People often have to listen to someone speak in the presence of competing voices. Much is known about the acoustic cues used to overcome this challenge, but almost nothing is known about the utility of cues derived from experience with particular voices—cues that may be particularly important for older people and others with impaired hearing. Here, we use a version of the coordinate-response-measure procedure to show that people can exploit knowledge of a highly familiar voice (their spouse's) not only to track it better in the presence of an interfering stranger's voice, but also, crucially, to ignore it so as to comprehend a stranger's voice more effectively. Although performance declines with increasing age when the target voice is novel, there is no decline when the target voice belongs to the listener's spouse. This finding indicates that older listeners can exploit their familiarity with a speaker's voice to mitigate the effects of sensory and cognitive decline.

A tidal wave of recent research purports to have discovered that higher-level states such as moods, action capabilities, and categorical knowledge can literally and directly affect how things look. Are these truly effects on perception, or might some instead reflect influences on judgment, memory, or response bias? Here, we exploited an infamous art-historical reasoning error (the so-called \"El Greco fallacy\") to demonstrate that multiple alleged top-down effects (including effects of morality on lightness perception and effects of action capabilities on spatial perception) cannot truly be effects on perception. We suggest that this error may also contaminate several other varieties of top-down effects and that this discovery has implications for debates over the continuity (or lack thereof) of perception and cognition.

This study assessed impairments in spatial and temporal perception in individuals with bilateral vestibulopathy (BVP). A total of 30 BVP subjects and 35 healthy controls (CTL) participated in a series of tests to assess their perception of distance (1–6 meters), angle (90–360 degrees), duration (2–10 seconds), and a combination of distance and angle during a triangle completion task (TCT). When performing distance and angle perception tasks separately, the BVP subjects showed larger errors than the CTL subjects. During the TCT, the BVP subjects walked longer paths and exhibited greater angle deviations compared to the CTL subjects. The angle deviations of the BVP subjects during the TCT were larger than when the angle perception task was performed separately. Moreover, the BVP subjects demonstrated accurate time interval perception, whereas the CTL subjects did not. Although the vestibular system is crucial for balance and spatial awareness, the proprioceptive system, in combination with visual and cognitive strategies, as well as motor efference copies, can help individuals with labyrinthine defects in separately perceiving distances and angles. However, this compensatory approach becomes less effective when these tasks are combined. These findings are relevant for space (planetary) exploration because exposure to microgravity mimics loss of vestibular otolith function.