A new illusion: The underestimation of distance during pursuit eye movements

A new visual illusion is reported. The apparent distance through which a displaced target appears to move is significantly shorter when pursuit tracked than when that same distance is observed by means of a saccadic eye movement. This misperception of distance seems to be related to the Aubert-Fleischl paradox, the underestimation of the velocity of a tracked target, and to reveal a consistent characteristic of the pursuit eye movement system.     

The dissociation of position and extent in Müller-Lyer figures

Three experiments were designed to determine whether Müller-Lyer figures cause a misperception of the positions of their fins and, if they do, whether it is commensurate with the distortion of extent. Observers marked the visible intersection of shaft and fins either with their unseen hands or with their visible hands after the figure had been removed from view. In the former case, no systematic distortions of position were evident. In the latter case, there were small, systematic distortions of position, which were significantly smaller when the observers fixated the target vertex than when they fixated the center of the figure. These differences are discussed in terms of the probable similarities between the control of eye movements and the control of pointing responses. Of particular importance is the finding that even the largest distortions of vertex position were much smaller than the distortions of shaft extent. The results appear to provide evidence of the independence of perceived position from perceived extent in Müller-Lyer figures and to contradict all existing theories of the illusion.     

Assessing different aspects of pretend play within a play setting: Towards a standardized assessment of pretend play in young children

The present study suggests a method with which to assess the interrelations between different types of pretend play. In contrast to standard methods in this area, the various types of pretend play were measured within an interactive play scenario. The pretend play tasks were included in a semi‐structured play sequence and presented to young children between 24 and 30 months of age (N=30). Self‐ and doll‐directed pretence, object substitution, pretence with realistic objects, and self‐initiated pretend play, as well as the understanding that an object had been given two identities was tested. The capacity for dual representation was assessed by asking for the real and pretend identity of an object. Age differences were found in the overall score for elicited pretence but not for all items separately. Individual items also differed in difficulty and thus are of potential use for assessing intraindividual differences in pretend play. Findings are discussed in the context of current theories and methods concerning the development and assessment of pretend play.     

Prolonged inactivation of the hippocampus reveals temporally graded retrograde amnesia for unreinforced spatial learning in rats

We investigated whether systems consolidation of spatial memory could be detected in a non-navigational, spatial-learning test that takes advantage of rats’ natural propensity to preferentially investigate an object that was displaced relative to spatial cues more than an object that remained stationary. Previous studies using navigational spatial-learning tests have generally failed to reveal temporally-graded retrograde amnesia, possibly because the hippocampus needs to be intact for the retrieval and/or processing of navigational information during the test. In the present study, the hippocampus of rats was kept inactivated, at two sites along its septo-temporal axis (dorsal and intermediate), for four consecutive days, beginning either 3 h or 5 days after familiarization to two identical objects in an open field. Rats that had their hippocampus inactivated beginning 5 days but not 3 h after familiarization showed evidence that they remembered the previous location of the displaced object. The results suggest that systems consolidation of spatial memories can be detected using a non-navigational test of spatial memory.     

Motion aftereffects and retinal motion

Two experiments are described in which it was investigated whether the adaptation on which motion aftereffects (MAEs) are based is a response to retinal image motion alone or to the motion signal derived from the process which combines the image motion signal with information about eye movement (corollary discharge). In both experiments observers either fixated a stationary point or tracked a vertically moving point while a pattern (in experiment 1, a grating; in experiment 2, a random-dot pattern) drifted horizontally across the field. In the tracking condition the adapting retinal motion was oblique. In the fixation condition it was horizontal. In every case in both conditions the MAE was horizontal, in the direction opposite to that of pattern motion. These results are consistent with the hypothesis that the adaptation is a response to the motion signal derived from the comparison of eye and image motion rather than to retinal motion per se. An alternative explanation is discussed.     

Change blindness and priming: When it does and does not occur

In a series of three experiments, we explored the nature of implicit representations in change blindness (CB). Using 3 x 3 letter arrays, we asked subjects (Ss) to locate changes in paired arrays separated by 80 ms ISIs, in which one, two or three letters of a row in the second array changed. In one testing version, a tone followed the second array, signaling a row for partial report (PR). In the other version, no PR was required. After Ss reported whether a change had been detected and the PR had been completed (if required), they were asked to identify a degraded letter trigram that was either novel, or from a previously shown row (repetition priming). Our findings indicate that when CB occurs, both the pre-change and post-change stimulus information primes despite its unavailability to consciousness. Surprisingly, findings also indicate that when change detection occurs only the post-change information primes.     

Experiences of being homeless or at risk of being homeless among Canadian youths

A qualitative study was undertaken with four groups--immigrants, youths, Aboriginal people, and landlords--in order to explore, compare, and contrast diversity issues among the homeless population and those at risk of homelessness in a larger Canadian city (Calgary, Alberta) with a smaller city (Lethbridge, Alberta), to better understand their and to needs make recommendations for improvement in service delivery and policy formation. This paper focuses on the findings from our sample of youths who shared information on a range of factors that contributed to their being homeless or at risk of being homeless. The youths in this study also shared their positive as well as negative experiences with educators, peers, family members, and social service providers. Canada's homeless include growing numbers of young people, families, women, and members of various ethnic communities, including Aboriginal people and immigrants. Today it is no longer possible to articulate a single silhouette of the homeless, but rather a diversity of profiles is needed. It was in the light of this reality that a study, "Diversity Among the Homeless and Those At Risk," was carried out. It was undertaken with four groups--immigrants, youths, Aboriginal people, and landlords.     

The prediction of stress by values and value conflict

The authors investigated the relationships among stress, values, and value conflict. Data collected from 400 people working in a variety of companies in Flanders indicated that the values of openness to change, conservation, self-transcendence, and self-enhancement were important predictors of stress. Participants open to change reported less stress, whereas participants who had high scores on conservation, self-enhancement, and self-transcendence perceived more stress. People who reported high value conflict also experienced more stress. Separate analyses for men and women showed that there were gender differences in the relationships observed between the 4 value types and stress. These data have noteworthy theoretical and practical implications.     

Saccadic inhibition in reading

In 5 experiments, participants read text that was briefly replaced by a transient image for 33 ms at random intervals. A decrease in saccadic frequency, referred to as saccadic inhibition, occurred as early as 60-70 ms following the onset of abrupt changes in visual input. It was demonstrated that the saccadic inhibition was influenced by the saliency of the visual event (Experiment 3) and was not produced in response to abrupt but irrelevant auditory stimuli (Experiment 1). Display changes restricted to an area either inside or outside the perceptual span required for normal reading produced strong saccadic inhibition (Experiment 2). Finally, Experiments 4 and 5 demonstrated higher level cognitive or attentional modulation of the saccadic inhibition effect.