Looking for more food or more people? Task context influences basic numerosity perception

Psychophysics over the counter: The effect of food preference on the perception of food quantity

Much research in food psychology has examined the influence of perceptual features - color, texture, packaging - on preference for that food. Here, we addressed the reverse question of the influence of food preference on the perception of its quantity. Does a portion of a loved food appear different than the same portion of a hated food? We probed this question by employing state-of-the-art tools of psychophysics, which allowed us the parallel examination of several long-standing issues of psychophysics. The latter included the difference between symbolic and non-symbolic number, the difference between the methods of Magnitude Estimation and Magnitude Production, the difference between under- or over-estimation and rate of growth measured by the (slope of) psychophysical function as well as the derivation of the Difference Threshold by the method of Constant Stimuli. We addressed the question of an effect on perception of food valence with four distinct experiments. Presenting real food items, we found that perceived quantity is a compressive function of objective quantity regardless of valence; both loved- and hated-food dynamics are governed by Stevens' power function with an exponent of 0.8. In absolute terms, applying Magnitude Estimation, we witnessed a gross underestimation for loved and hated food alike. In contrast, applying Magnitude Production, participants underproduced loved food, but overproduced hated food. For discrimination of food quantity, we found better resolving power for hated food. Collectively, our results show that, across diverse psychophysical evaluations, food valence affects its perception, especially when people actively regulate the to-be-consumed portion.

Number sense biases children's area judgments

Humans are thought to use the approximate number system (ANS) to make quick approximations based on quantity even before learning to count. However, there has long been controversy regarding the salience of number versus other stimulus dimensions throughout development, including a recent proposal that number sense is derived from a sense of general magnitude. Here, we used a regression approach to disentangle numerical acuity from sensitivity to total surface area in both 5-year-old children and adults. We found that both children and adults displayed higher acuity when making numerosity judgments than total surface area judgments. Adults were largely able to ignore irrelevant stimulus features when making numerosity or total area judgments. Children were more biased by numerosity when making total area judgments than by total area when making numerosity judgments. These results provide evidence that number is more salient than total surface area even before the start of formal education and are inconsistent with the Sense of Magnitude proposal.

Neural Dynamics of Serial Dependence in Numerosity Perception

Serial dependence—an attractive perceptual bias whereby a current stimulus is perceived to be similar to previously seen ones—is thought to represent the process that facilitates the stability and continuity of visual perception. Recent results demonstrate a neural signature of serial dependence in numerosity perception, emerging very early in the time course during perceptual processing. However, whether such a perceptual signature is retained after the initial processing remains unknown. Here, we address this question by investigating the neural dynamics of serial dependence using a recently developed technique that allowed a reactivation of hidden memory states. Participants performed a numerosity discrimination task during EEG recording, with task-relevant dot array stimuli preceded by a task-irrelevant stimulus inducing serial dependence. Importantly, the neural network storing the representation of the numerosity stimulus was perturbed (or pinged) so that the hidden states of that representation can be explicitly quantified. The results first show that a neural signature of serial dependence emerges early in the brain signals, starting soon after stimulus onset. Critical to the central question, the pings at a later latency could successfully reactivate the biased representation of the initial stimulus carrying the signature of serial dependence. These results provide one of the first pieces of empirical evidence that the biased neural representation of a stimulus initially induced by serial dependence is preserved throughout a relatively long period.

Serial dependence in numerosity perception

Our conscious experience of the external world is remarkably stable and seamless, despite the intrinsically discontinuous and noisy nature of sensory information. Serial dependencies in visual perception-reflecting attractive biases making a current stimulus to appear more similar to previous ones-have been recently hypothesized to be involved in perceptual continuity. However, while these effects have been observed across a variety of visual features and at the neural level, several aspects of serial dependence and how it generalizes across visual dimensions is still unknown. Here we explore the behavioral signature of serial dependence in numerosity perception by assessing how the perceived numerosity of dot-array stimuli is biased by a task-irrelevant "inducer" stimulus presented before task-relevant stimuli. First, although prior work suggests that numerosity perception starts in the subcortex, the current study rules out a possible involvement of subcortical processing in serial dependence, confirming that the effect likely starts in the visual cortex. Second, we show that the effect is coarsely spatially localized to the position of the inducer stimulus. Third, we demonstrate that the effect is present even with a stimulus presentation procedure minimizing the involvement of post-perceptual processes, but only when participants actively pay attention to the inducer stimulus. Overall, these results provide a comprehensive characterization of serial dependencies in numerosity perception, demonstrating that attractive biases occur by means of spatially localized attentional modulations of early sensory activity.