Perceptual Studies

This paper addressed what matters most in research. These include choice of appropriate statistic and data interpretation. It also provided explanation to some confusing terminologies including those whose use in some contexts are subject of debate.

In this article the problem of perception is highlighted from a philosophical, physiological and psychological point of view. The essay (second update) is followed by a list of publications, journals and websites about perception. The author would be delighted to receive comments. He can be contacted at j[underscore]kuijper[at]online[dot]nl.

Illusions provide a window into the brain’s perceptual strategies. In certain illusions, an ostensibly task-irrelevant variable influences perception. For example, in touch as in audition and vision, the perceived distance between successive punctate stimuli reflects not only the actual distance but curiously the inter-stimulus time. Stimuli presented at different positions in rapid succession are drawn perceptually towards one another. This effect manifests in several illusions, among them the startling cutaneous rabbit, in which taps delivered to as few as two skin positions appear to hop progressively from one position to the next, landing in the process on intervening areas that were never stimulated. Here we provide an accessible step-by-step exposition of a Bayesian perceptual model that replicates the rabbit and related illusions. The Bayesian observer optimally joins uncertain estimates of spatial location with the expectation that stimuli tend to move slowly. We speculate that this expectation – a Bayesian prior – represents the statistics of naturally occurring stimuli, learned by humans through sensory experience. In its simplest form, the model contains a single free parameter, tau: a time constant for space perception. We show that the Bayesian observer incorporates both pre- and post-dictive inference. Directed spatial attention affects the prediction-postdiction balance, shifting the model’s percept towards the attended location, as observed experimentally in humans. Applying the model to the perception of multi-tap sequences, we show that the low-speed prior fits perception better than an alternative, low-acceleration prior. We discuss the applicability of our model to related tactile, visual, and auditory illusions. To facilitate future model-driven experimental studies, we present a convenient freeware computer program that implements the Bayesian observer; we invite investigators to use this program to create their own testable predictions.

Multisensory Sensemaking: Children’s Exploratory Behavior has Organizing Structure at Micro- and Macro-scales Nancy Owens Renner ([email protected]) Department of Cognitive Science, University of California San Diego 9500 Gilman Drive, La Jolla, CA USA 92093-0515 Abstract • situated, i.e. physical, social, cultural, and historical contexts all play a role in cognition; • distributed, i.e. cognition at every scale manifests in nested systems with interacting parts. People live and act in cognitive ecosystems, in which brains, bodies, cultural and material worlds all exert mutual cognitive influence in any given moment and as they change over time (Hutchins, 2010). Distributed cognition provides a unifying principle. When children encounter museum exhibits, they find rich opportunities for action, perception, learning, and other forms of cognition. Can we see systematic organization in the children’s behavior, and by extension, their cognition? What would count as evidence of this orga...

In touch as in vision, perceptual acuity improves with training to an extent that differs greatly across people: even individuals with similar initial acuity may undergo markedly different improvement with training. What accounts for this variability in perceptual learning? We hypothesized that a simple physical characteristic – fingertip surface area – might constrain tactile learning, because previous research suggests that larger fingers have more widely spaced mechanoreceptors. To test our hypothesis, we trained 10 human participants intensively on a tactile spatial acuity task. During four days, participants completed 1900 training trials (38 50-trial blocks) in which they discriminated the orientation of square-wave gratings pressed onto the stationary index or ring finger, with auditory feedback provided to signal correct and incorrect responses. We progressively increased task difficulty by shifting to thinner groove widths whenever participants achieved ≥ 90%-correct block performance. We took optical scans to measure surface area from the distal inter-phalangeal crease to the tip of the finger. Participants’ acuity improved markedly on the trained finger, and to a lesser extent on the untrained finger. Crucially, we found that participants’ tactile spatial acuity improved towards a theoretical optimum set by their finger size: participants with worse initial performance, relative to their finger size, improved more with training, and post-training performance correlated better than did pre-training performance with finger size. These results strongly support the hypothesis that tactile perceptual learning is limited by finger size. We suspect that analogous physical constraints on perceptual learning will be found in other sensory modalities.