When we look at a flight of level stairs where its longitudinal section obliquely intersected the direction of treads, we perceive the stairs to be tilted laterally. We call this phenomenon a “skewed staircase illusion (SSI).” To investigate features of the SSI, using miniatures of skewed stairs or of laterally sloped planes, we measured their apparent lateral tilts. Main findings were: 1) the stairs were perceived to be less tilted than the laterally sloped planes, 2) the stairs of 32 steps were perceived to be more tilted than those of five steps, 3) the stairs were perceived to be more tilted when we looked them down from the top than when we looked them up from the base, and 4) the apparent tilt of the skewed stairs or laterally sloped planes had a positive correlation with cross-component of slope. We proposed that the SSI is affected by an apparent plane generated by perceptual connection of the treads of stairs.
We investigated output-monitoring errors in a modified source-monitoring paradigm. Unlike the traditional paradigm that involves two phases, learning and monitoring, the modified paradigm involves three phases, learning, enactment, and monitoring. Three experiments produced two major findings. First, compared with the traditional paradigm, the modified paradigm produced fewer monitoring errors. Second, performing a dual-task during the enactment phase increased monitoring errors for the items that participants repeatedly enacted during the learning phase. In contrast, performing a dual-task during the learning phase did not influence monitoring errors. It only decreased the number of items that were enacted during the enactment phase. We concluded that monitoring errors are more likely to occur (a) when the modality of items matches between the learning and enactment phases (i. e., items are enacted during both phases), and (b) when a dual-task increases processing demands during the enactment phase.
Previous studies have suggested that facial displays in the presence of others are influenced by the relationship with accompanying persons. In these studies, subjects participated with friends or strangers, without any focus on social interactions between partners. In the current study, pairs of friends or strangers viewed film clips expected to elicit positive and negative affects; the control group participated without partners. We measured synchronous smiles between partners as a social interactive display, in addition to the duration and the frequency of smiles and frowns. Subjective emotion and social motive were also measured. Smiles were facilitated by the presence of a friend than a stranger or the condition of lone participation, regardless of stimulus valence. Synchronous smiles and the communication motive were also enhanced with a friend than with a stranger. These results suggested that the expression of smiles was facilitated by the communication motive and social interactions between partners.
Although there have been a number of studies that theoretically and empirically examined altruism based on direct reciprocity, few have been conducted on how altruism based on indirect reciprocity emerges. Recent advances in biological research, however, have suggested possible answers to the question. For instance, Nowak and Sigmund (1998a, b) proposed that what they called image scoring strategy made indirect reciprocity possible. After critically examining their work, Leimar and Hammerstein (2001) pointed out several limitations to the theory, and instead proposed standing strategy as an explanation. Although careful attempts to replicate the findings by them and Panchanathan and Boyd (2003) supported the arguments against image scoring, we reveal that standing strategy was not a satisfactory answer either. Based on a series of evolutionary simulations, we propose a new strategy, which we call strict discriminator, as an alternative. Strict discriminators are discriminating altruists, similar to the altruists with image scoring or standing strategy, but they are different in that its criterion for discrimination is stricter: unconditional altruists are excluded from their reciprocity.
We examined the relationship between two properties of verbal probability (VP) expressions, “vagueness” and “directionality”, and investigated the effects of these properties on decision making. Vagueness is defined as its imprecise characteristic of uncertainty expressions in VP, whereas the directionality is communicative functions which cause one to focus on the occurrence or non-occurrence of the target event described by VP. Experiment 1 contrasted a disagreement in the literature as to whether one can predict the directionality from vagueness properties, and our analyses resolved the conflict by showing the ineffectiveness of the vagueness in predicting the directionality. Experiment 2 administered decision tasks involving VP and numerical translation tasks of VP. We discovered that the directionality affects only on decision tasks. The results of Experiments 1 and 2 indicated that the directionality is distinct characteristic from the vagueness of VP, and these properties affect decisions independently. Implications are discussed.