The present study examined whether participants were able to implicitly learn the non-existence, as well as the existence, of an invariant. In Experiment 1 the participants were exposed to 40 four-digit numbers and performed a distracter task. All the stimuli for the positive condition contained the invariant "3" (positive stimuli), but the stimuli for the negative condition did not (negative stimuli). The control stimuli contained an equal quantity of numbers (from 1 to 9). A pseudo-recognition memory task then followed. The participants in the positive condition then selected more positive stimuli than the chance level, but participants in the negative condition selected fewer positive stimuli than the chance level which was indicated by the participants in the control condition. Experiment 2 used "7" as the invariant, and produced the same results as Experiment 1. This study is the first that indicates an implicit learning of the non-existence, as well as existence, of an invariant. The significance and the problems of these results are discussed.
We can perceive the continuity of an object or event by integrating spatially/temporally discrete sensory inputs. The mechanism underlining this perception of continuity has intrigued many researchers and has been well documented in the visual and auditory modalities. Recently we reported that an illusion of continuity also occurs in the vibrotactile sensation. When brief temporal gaps inserted in a vibrotactile target are filled with vibrotactile noise, the target vibration is perceived to continue through the noise, if the target vibration is sufficiently weak relative to the noise. The illusory continuity of the vibration cannot be distinguished from the physically continuous vibration. The results suggest that the continuity illusion is common to multiple sensory modalities and that it reflects a general fundamental principle of our perception.
Temporal synchrony is a critical condition for integrating information coming from different sensory modalities such as vision, audition and touch. However, how we take correspondence between the signals coming from different sensory modalities is still unclear. This paper first summarizes a series of psychophysical experiments on audio-visual temporal synchrony perception, conducted by us over the past several years (Fujisaki, Koene, Arnold, Johnston, & Nishida, 2006; Fujisaki & Nishida, 2005, 2007, 2008; Fujisaki, Shimojo, Kashino, & Nishida, 2004), and introduces our proposed model for audio-visual synchrony detection (Fujisaki & Nishida, 2005). The latter part of the paper introduces some of our more recent works on crossmodal temporal synchrony perception including tactile modality, which compare temporal frequency limits obtained with synchrony-asynchrony discrimination experiments between audio-tactile, visuo-tactile, and audio-visual stimulus pairs.
Sensory perception has been traditionally investigated one modality at a time, but real world perception and behavior are driven by the integration of information from multiple sensory sources. In traditional models of the sensory brain, multisensory integration is deferred until after extensive unisensory processing has occurred. Rapidly accumulating evidence on multisensory processing in mammals challenges this classical view. Anatomical studies suggest that the substrate for multisensory integration is already present at the primary sensory cortices. Furthermore, it has been shown that the activity of auditory thalamus is strongly influenced by visual stimuli, when presented in conjunction with auditory stimuli. These findings strongly indicate that the neural underpinnings of multisensory integration extend into the very early stages of sensory processing.