Knowledge that Transforms

Auditory sequences of tones were used to examine a form of stimulus-driven attending that involves temporal expectancies and is influenced by stimulus rhythm. Three experiments examined the influence of sequence timing on comparative pitch judgments of two tones (standard, comparison) separated by interpolated pitches. In two of the experiments, interpolated tones were regularly timed, with onset times of comparison tones varied relative to this rhythm. Listeners were most accurate judging the pitch of rhythmically expected tones and least accurate with very unexpected ones. This effect persisted over time, but disappeared when the rhythm of interpolated tones was either missing or irregular.

How do people control locomotion while their eyes are simultaneously rotating? A previous study found that during simulated rotation, they can perceive a straight path of self-motion from the retinal flow pattern, despite conflicting extraretinal information, on the basis of dense motion parallax and reference objects. Here we report that the same information is sufficient for active control ofjoystick steering. Participants steered toward a target in displays that simulated a pursuit eye movement. Steering was highly inaccurate with a textured ground plane (motion parallax alone), but quite accurate when an array of posts was added (motion parallax plus reference objects). This result is consistent with the theory that instantaneous heading is determined from motion parallax, and the path of self-motion is determined by updating heading relative to environmental objects. Retinal flow is thus sufficient for both perceiving self-motion and controlling self-motion with a joystick; extraretinal and positional information can also contribute, but are not necessary.

Four-month-old infants were exposed to sequences in which a 2-s light stimulus alternated with dark interstimulus periods whose length was manipulated to be 3 or 5 s. A predictable on-off pattern occurred for eight trials, but the light stimulus was omitted on the ninth trial. Infants showed heart rate responses on the omission trial that were closely synchronized with the expected recurrence of the stimulus. In addition, these heart rate patterns were observed predominantly in infants who had previously shown high levels of sustained attention in pretests with visual stimuli. These findings indicate remarkable precision in infants' estimation of time intervals, and suggest that the link between time estimation and attentional processes is present in early infancy.

Lightness induction can occur on the basis of the immediate surround of a region (local interactions) and also on the basis of global factors of perceptual organization. The experiments reported in this article used novel displays that made it possible to differentiate the contributions of these two kinds offactors. The experiments demonstrated, for the first time, that when higher-level factors act contemporaneously with lower-level factors, the contrast effect induced by the global-organization principle of perceptual belongingness overcomes the effect due to retinal lateral inhibition.

The relation between source monitoring and suggestibility was examined among preschool children. Thirty-two 3- to 5-year-olds were simultaneously presented with a brief story in two different modalities, as a silent video vignette and a spoken narrative. Each modality presented unique information about the story, but the information in the two versions was mutually compatible. The children were then asked a series of questions, including questions about the source (modality) of story details, and leading questions about story details (to assess suggestibility). Performance on the source-monitoring questions was highly correlated with the ability to resist suggestion. In addition, children who were asked source-monitoring questions prior to leading questioning were less susceptible to suggestion than were those who were asked the leading questions first. This study provides evidence that source monitoring can play a causal role in reducing the suggestibility of preschool children.

We tested the strong form of the perceptual-load hypothesis, which posits that the amount of perceptual load is the only factor determining whether attention can be effectively focused. Participants performed a visual search task under conditions of low and high load and with either a 100% valid spatial cue or no spatial cue. With no cue, participants showed evidence of processing to-be-ignored stimuli when perceptual load was low but not when it was high, consistent with the perceptual-load hypothesis. However with a 100% valid spatial cue, participants showed little evidence of processing to-be-ignored stimuli, even when perceptual load was low. These results suggest that although perceptual load may be an important factor in attentional selectivity, load alone is not sufficient to explain how and when selective attention is effective.

Do participants in the Deese, Roediger, and McDermott (DRM) procedure demonstrate false memory because they think of nonpresented critical words during study and confuse them with words that were actually presented? In two experiments, 160 participants studied eight visually presented DRM lists at a rate of 2 s or 5 s per word. Half of the participants rehearsed silently: the other half rehearsed overtly. Following study, the participants' memory for the lists was tested by recall or recognition. Typical false memory results were obtained for both memory measures. More important, two new results were observed. First, a large majority of the overt-rehearsal participants spontaneously rehearsed approximately half of the critical words during study. Second, critical-word rehearsal at study enhanced subsequent false recall, but it had no effect on false recognition or remember judgments for falsely recognized critical words. Thinking of critical words during study was unnecessary for producing false memory.

Disagreements between psychologists and economists about the need for and size of financial incentives continue to be hotly discussed. We examine the effects of financial incentives in a class of interactive decision-making situations, called centipede games, in which mutual trust is essential for cooperation. Invoking backward induction, the Nash equilibrium solution for these games is counterintuitive. Our previous research showed that when the number of players in the centipede game is increased from two to three, the game is iterated in time, the players are rematched, and the stakes are unusually high, behavior approaches equilibrium play. Results from the present study show that reducing the size of the stakes elicits dramatically different patterns of behavior. We argue that when mutual trust is involved, the magnitude of financial incentives can induce a considerable difference.

Do men seek more short-term mates than women? Buss and Schmitt (1993) showed a pattern of mean difference in the ideal number of sexual partners men and women desired over various time frames. We replicated these mean sex differences (e.g., ideal number over the next 30 years: Ms = 7.69 and 2.78 for men and women, respectively), but in both data sets the sampling distributions were highly skewed. In Study 1, we found few sex differences in medians across time frames (e.g., ideal number over the next 30 years: Mdn = 1 for both men and women). In Study 2, most college men (98.9%) and women (99.2%) said they wanted to settle down with one mutually exclusive sexual partner at some point in their life, ideally within the next 5 years. Neither medians in number of partners desired overall before settling down (replicating Study 1) nor medians in short-term partners desired before settling down (Mdn = 0) differed significantly by gender. Rather, men and women concurred: Short-term mating is not what humans typically seek.