Clemson 2000 Posters



Affordances and the Accuracy of Visual Estimates of Size

Thomas R. Alley & Theodora S. Passinos

Clemson University

Two methods of estimating size (linear extent) were compared. One required adjustment of the distance between a point created by a laser beam and a fixed reference line; the other involved adjusting the separation of two vertical posts. Two groups of adults were instructed to use these methods to indicate either simple linear extent (“width”) or the affordance of passability (minimal opening) for identical dimensions of objects and their own bodies. Higher accuracy was expected for both the method (posts) and instructions (“opening”) that should foster affordance-based judgements. Despite the greater ease and precision of the laser-based method, more accurate estimates were made using two vertical posts.




The Doctoral Students of James J. Gibson and Eleanor J. Gibson

Patrick A. Cabe

University of North Carolina at Pembroke

Scholars are often noted both because of the work they produce and because of the students they train. Between them, James J. Gibson and Eleanor J. Gibson, over long academic careers, supervised approximately 40 doctoral dissertations. This poster presents a compilation of the names and dissertation titles of those students. Because some gaps remain in this list, it should be considered a work in progress. While some of the Gibsons’ students have pursued aims other than academia or research, a number of those individuals have gone on to establish respected research careers of their own in perception and perceptual development. Some other individuals who have had a close working relationship with one or the other of the Gibsons, but whose dissertations were not supervised by either James or Eleanor Gibson, are also listed.




Detecting Surface Aberrations in a Tool Task by Capuchin Monkeys (Cebus Apella)

Sarah E. Cummins-Sebree & Dorothy M. Fragaszy

University of Georgia

We examined four capuchins’ abilities to accommodate their actions to surface aberrations when manipulating a hoe to slide food across a platform. The platforms presented varied in being a) flat, b) containing a hole, and c) containing a barrier. Capuchins avoided barriers more than holes in early testing. They succeeded with both plain and barrier platforms throughout testing. By the conclusion of testing, two capuchins accommodated their actions sufficiently to succeed with hole platforms. Capuchins learn the affordances of varying surfaces and actions for successful use of tools.




Three Perspectives of AIDS

Judith Effken & Mary Koithan

University of Arizona College of Nursing

We describe three perspectives relevant to assessing patients with HIV. The clinician’s perspective is biomedically driven, based on goals, skills, and the healthcare reimbursement environment. Patients offer two additional perspectives. The cognitive perspective is found in patients’ stories, colored by education, culture and family history. The perceptual perspective, reflecting embodied experience in the world, is not typically accessed and is best captured through aesthetic representations. A sample of visual representations of persons living with HIV revealed a number of shared properties (shape, color, space & spacing, symmetries). We speculate that these similarities represent the invariant structure of their world.

Detection of Aperture Size and Location using Echolocation

Terri Erwin & Danielle Wassam

Wheeling Jesuit University

The acoustic perception of spatial layout by sighted humans was investigated in two experiments. Specifically, participants’ ability to use reflected sound to apprehend the dimensions of an enclosure was examined. Inside a chamber with sound reflecting walls, subjects produced “hooting” sounds and used the acoustic reflection to judge the size (Experiment 1) and location (Experiment 2) of an aperture in the wall facing them. Congruent with past research with blind and sighted subjects, we found variability in participants’ ability to echolocate successfully; however, our data indicate systematic performance for many participants in aperture size and location ranking, though absolute accuracy was not achieved.




Role of Dynamic Touch in Tool Use Development

Paula Fitzpatrick

Assumption College

During the toddler and preschool years children gain proficiency using a variety of tools-spoons, crayons, and shovels, for example. Lacking, however, is an understanding of the role of perception-particularly dynamic touch-in tool use development. Knowing the location of the end of a hand-held object is fundamentally crucial for successfully using it. In this experiment, perceptual measures were taken of children’s ability to perceive the length of an unseen, hand-held object. Drawing ability was used as an index of tool-use skill level. Results indicate that children are able to perceive the extent of a hand-held object, with subtle changes in perceptual sensitivity as a function of skill level. In addition, perception of extent was shown to vary as a function of the inertia of the object.




Perceiving the Lengths of Nonrigid Objects by Dynamic Touch

Desiré GrandPre & Claudia Carello

Center for the Ecological Study of Perception and Action, U of Connecticut

Haptically perceiving the lengths of rigid objects is constrained by the inertia tensor. When the wielded objects are nonrigid, however, tissue is deformed by more than the object’s mass distribution (e.g., oscillatory motions of an object, influenced by its stiffness, are superimposed on exploratory movements). Two experiments examined perception of spring length by dynamic touch. As with rigid objects, perceived length approximated actual length and was constrained by two moments of inertia whose exponents were opposite in sign. Moreover, the contribution of an index of stiffness was significant (with a negative exponent) for both plain springs and springs attached to rigid handles.




Adapting to Change in Complex Work Environments

John R. Hajdukiewicz

University of Toronto

The purpose of this research is to assess the impact of human-computer interfaces on an operator’s ability to adapt to change. A study was conducted using DURESS II, a thermal-hydraulic microworld environment. Participants used one of two interfaces to control the process system, developed using different design principles. After a great deal of practice, their abilities to achieve the target states, in the face of global, dynamic perturbations, were examined. The data were analyzed using measures of adaptive performance, coupling to the work environment, and stability. The results show that information and experience are key factors to success in adapting to change.

Identification of Positive and Negative Behaviours Associated with Operating a Cellular or Mobile Phone Whilst Driving

Philip Hovea, Gillian H. Gibbsb, & Jeff K. Cairda

aUniversity of Calgary bSimon Fraser University

Although using a cellular or mobile phone while driving is likely to increase accident risk (Goodman, et al., 1997, Redelmeier and Tibshirani, 1997; Violanti and Marshall, 1996), little is actually known about when and why drivers use their phones while driving. Dialing a long number or arguing with a spouse on the phone when the traffic environment is particularly demanding exemplify several behaviours not suited to driver safety. However, being able to call the police after an accident occurs or requesting a tow truck after breaking down are positive behaviours associated with using a mobile phone (Goodman, et al., 1997). On a situation by situation basis, some drivers may and others may not attempt to balance the attentional demands of using the phone with the varying demands of driving. Others may make strategic decisions when it is or is not safe to use a phone such as not in high traffic urban areas or at intersections. We hypothesized that those that are willing to commit violations in high risk driving situations such as running yellow lights (see, e.g., berg, et al., 1998; Parker, et al., 1992; 1995; Reason, et al., 1990) would also be more likely to use mobile phones when it was less safe to do so. The purpose of this study was to develop and test a measurement instrument that could test this hypothesis.




Age-Related Variation in Driving behavior At Night

D. Alfred Owensa, Justin M.. Owensa, Joanne Woodb, Daniel Whittamb, & Mark Woolfb

aFranklin & Marshall College

bQueensland University of Technology

Road fatality rates are 3 to 4 times higher at night than in the day, and impaired vision is a major contributing factor. Moreover, problems of night vision are greater for older drivers, the fastest-growing segment of the driving population. Accordingly, this study tested performance during driving on a closed road course to assess the effects of age and low illumination, the two factors that most commonly impair vision when driving. Visual recognition of naturalistic targets is degraded during night driving, and this problem increases with advancing age. Risks for pedestrians, who are especially difficult to see at night, are minimized by biological motion markings. Measures of speed and lane keeping suggest that older drivers attempted to compensate for age-related impairments of night vision through more cautious behavior. All ages drove more slowly in low light, but none slowed enough to compensate for decreased visibility. These findings support the hypothesis that driving behavior depends less on visual recognition (focal) than on visual guidance (ambient) processes, which evolved to provide efficient control of actions.




Relating Errors in Verbal and Reaching Responses to Visual Targets

Christopher C. Pagano, Richard P. Grutzmacher, & Joseph C. Jenkins

Clemson University

It has recently been suggested that different responses to visually perceived targets, such as verbal responses and blind walking, are directed by a single internally represented perceived depth. Evidence for this is provided by the fact that verbally reported distances are essentially a single-valued function of distance reported by an action response. An alternative procedure is to compare verbal and action responses that are made at the same time (i.e. within-trial). Specifically, participants can be asked to make a verbal judgment to a given target distance which is immediately followed by an action response. The results suggest that ‘cognitive’ and motor responses to visually perceived targets, such as verbal responses and blind reaches, respectively, are not directed by a single internally represented perceived depth when those responses are initiated immediately. With a delay, however, it is possible that the two responses may become correlated.

Visual Judgements of Wheelchair Passability: Influence of Control and Point of View

Michael K. Russellab & Stacy Lopresti a

aKutztown University bBucknell University

Flascher, Kadar, Garrett, Meyer, and Shaw (1995) have shown that passability judgments of physical extensions of the body (e.g., cars, wheelchairs) are a function of the observer’s intention and can be as accurate as body-scaled judgments. In the present studies, participants were given the task of judging whether a gap affords passage for a wheelchair. The contributions of chair control (own versus another’s control) and point of observation were evaluated. Results revealed that while passability judgments were essentially independent of the point of observation, the control of the wheelchair was a significant factor. The importance of perspective and intention are discussed.




Auditory Perception of Reachability: Interaction Between Earheight and Traditional Information Factors

Michael K. Russellab & Kerri Schulera

aKutztown University bBucknell University

Eye height has been shown to affect visual perception. While the present study revealed that ear height influenced auditory perception, visual and auditory judgments of reachability were found to be differentially affected by the manipulation of the point of observation. The extent to which binaural differences, sound intensity, and the ratio of direct to indirect sound influenced distance judgments when ear height and target height were not equivalent was also determined. The results suggest that it is only the amount of direct sound energy reaching the ear that is informative about source distance when target height is below ear height.




Auditory Perception of Reachability: Sound Intensity and Ratio of Direct-to-Indirect Sound

Michael K. Russellab & Kerri Schulera

aKutztown University bBucknell University

It has been previously shown that observers are highly capable of judging the reachability of an unseen sound source. The present study sought to determine the extent to which sound intensity and the ratio of direct to indirect sound influence reachability judgments. While the results suggest that both factors affect perceptual judgments, sound intensity appears to be a scaling factor whereas this was not the case for direct:indirect sound energy. The possibility exists that a higher-order variable, a variable capturing both factors, serves as the basis of auditory distance perception.




The Effect of the Hand in the Body Cavity on a Laporoscopic Surgical Task

Richard Schmidt, Nicole Gribbons, & Brian Eckert

College of the Holy Cross, Worcester, MA

This study investigated whether the performance of a video-guided surgical task using the dominant hand is enhanced by the presence of the nondominant hand inside of the body cavity. In a series of experiments, performance of a manual task using one hand alone was compared to the performance of the task when the participants had their nondominant hand inside the body cavity either invisibly, or visibly and playing a passive role or visibly and playing an active role in the task. Results using three different manual tasks suggest that having the hand play an active role decreased the difficulty of the task whereas having the hand in a position invisible to the participant caused a deficit in task performance. The results have implications for the use of the HandPort Surgical System developed recently by Smith and Nephew Endoscopy.

Variations of Mass and Static Moment are Not Necessary for Variations in Perceived Heaviness: An Affordance Perspective on the Inertia Tensor

Kevin D. Shockley, Claudia Carello, & M. T. Turvey

Center for the Ecological Study of Perception & Action, University of Connecticut

Haskins Laboratories

Two scalars derived from the inertia tensor have been shown to play a role in heaviness perception: Inertia ellipsoid volume relates to the mean level of torque needed to move an object; inertia ellipsoid symmetry concerns how that torque should be directed. Previous research has found that the influences of these scalars on perceived heaviness are additive. Since static moment, SM, also varied, three new experiments assessed whether perceived heaviness varies in the absence of variations of mass and SM. The tensor hypothesis was supported. Given their relevance to the human movement system, symmetry and volume provide an affordance-based description of objects.





Tell Me How to Move

Kevin D. Shockleyab, Marie-Vee Santanaa, & Carol Fowlerb

aCenter for the Ecological Study of Perception & Action, University of Connecticut

bHaskins Laboratories

Biological organisms exhibit phase-locking or synchronization at different time scales. The behavior of fireflies, for instance, as well as that of other biological organisms has been observed to exhibit collective patterns (c.f., Strogatz & Stewart, 1993, Schmidt & O_Brien, 1997). The present research will report evidence of entrainment as a function of speech and communication using the wrist-pendulum paradigm and postural activity (measured using 6-D motion capture technology). The experiments discussed here utilize independent and cooperative speech tasks to investigate the influence of these on action. Our goal is to better understand the constraints that oral communication imposes on coordination.





Postural Stabilization of Vision with Imposed Optical Flow

Mei Sia, Gregory K. Nelsona, Philip Hovea, Thomas A. Stoffregena, & Benoit G. Bardyb

aUniversity of Cincinnati bUniversity of Paris XI

Are postural responses to imposed optical flow functionally related to the demands of simultaneous supra-postural tasks? Standing subjects were exposed to imposed optical flow in a moving room. In Experiment 1 subjects were instructed to intentionally resist the effects of room motion on stance; this effort yielded a significant reduction in coupling. In Experiments 2 and 3 subjects performed an explicit supra-postural visual task, either fixation of a textured target, or scanning a text for target letters. Targets either shared the room’s motion or were stationary relative to the earth. Coupling of body sway to room motion was reduced with stationary targets.

Clinical Utility of Postural Dynamics

L. James Smart, Jr. & Dean L. Smith

Miami University, OH

Recently, evidence linking behavioral and health research has emerged from the study of posture and postural dynamics. Studies examining the relation between postural control and motion sickness has shown that motion sickness is preceded and predicted by postural instability (Stoffregen & Smart, 1998; Stoffregen et al, in press; Smart, 2000). Motion sickness is characterized by maladaptive response to unusual motion events (Reason & Brand, 1975). Symptomology is non-specific and variable. While the Postural instability theory of motion sickness proposed by Riccio and Stoffregen (1991) predicted that instability should precede sickness, they did not make any claims regarding the symptomology associated with it. Chiropractic literature has emphasized the effects of vertebral subluxation on neurological dysfunction. Vertebral subluxation is a condition that is postulated to interfere with neurological processes and may influence organ system function and general health. As in the case of motion sickness, symptomology is non-specific and variable (and in some instances the person may be asymptomatic). So what do these disorders have in common? In each instance the disruptions lead to inefficiency in the system. We will discuss this link in the poster.




The Affordances of Conversation: Interrupting and Self-Disclosure

S. Stavros Valenti

Hofstra University

Gibson’s ecological approach has much to offer the study of social development because it redirects attention away from hypothetical mental representations and steps of information processing. Instead, it stresses the discovery of what people actually do together and the informational bases of social behavioral regulation. In this presentation I will discuss recent thinking on the nature of social affordances as entities distinct from the affordances of places, pathways, dwellings, and objects. The idea of social (communicative) affordances will be illustrated with two lines of research: Dunn and Shatz’s 1989 study of young children’s interrupting, and our own research on the sequential structure of self-disclosure in the conversations of adolescent friends.