Stephen Dopkins

The Psychonomic Society, Society Hill, New Jersey, United States

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Publications (34)83.11 Total impact

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    ABSTRACT: In manipulating a pointer to indicate subjective straight ahead (SSA), participants were more variable after a series of whole-body rotations in conjunction with external sensory blockade than after external sensory blockade alone. The variability of reported SSA did not increase consequent to a temporal delay matched to the time taken by the rotation procedure. These results suggest that an observer's egocentric reference frame is more complex and less stable than has previously been thought.
    Memory & Cognition 08/2014; · 1.92 Impact Factor
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    Stephen Dopkins, Jesse Sargent
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    ABSTRACT: In an exploration of the process whereby horizontal and vertical components are extracted from distances between pairs of points, participants made speeded absolute distance judgments-deciding whether horizontal distances between pairs of points in a frontal plane exceeded a criterion distance. Judgments reflected the horizontal and vertical distances between the points. Three accounts of the results were considered. (1) Only the overall distance between two points was directly available to judgment processes; the horizontal or vertical distance between the points was available only to the extent that the horizontal and vertical positions of the points were differentially weighted prior to the assessment of overall distance. (2) The perceptual effects of positions on the horizontal and vertical dimensions were collapsed onto a composite dimension. (3) The decision criterion for the distance judgment considered both the horizontal and vertical distances between the points. In support of the overall distance account, (1) performance in the distance judgment task was facilitated by repetition of the same overall distance from trial to trial, but not by repetition of the distance on the composite dimension or by repetition of horizontal or vertical distance; (2) differential weighting that the overall distance account predicted for the absolute distance judgments was reflected in concurrent relative distance judgments pitting horizontal against vertical distance, counter to the composite dimension account, which sees the horizontal and vertical dimensions as collapsing onto the composite dimension in balanced, symmetrical fashion, and counter the decisional account, given that no criterion is required for the relative judgment.
    Attention Perception & Psychophysics 11/2013; · 1.97 Impact Factor
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    ABSTRACT: We explored a system that constructs environment-centered frames of reference and coordinates memory for the azimuth of an object in an enclosed space. For one group, we provided two environmental cues (doors): one in the front, and one in the rear. For a second group, we provided two object cues: a front and a rear cue. For a third group, we provided no external cues; we assumed that for this group, their reference frames would be determined by the orthogonal geometry of the floor-and-wall junction that divides a space in half or into multiple territories along the horizontal continuum. Using Huttenlocher, Hedges, and Duncan's (Psychological Review 98: 352-376, 1991) category-adjustment model (cue-based fuzzy boundary version) to fit the data, we observed different reference frames than have been seen in prior studies involving two-dimensional domains. The geometry of the environment affected all three conditions and biased the remembered object locations within a two-category (left vs. right) environmental frame. The influence of the environmental geometry remained observable even after the participants' heading within the environment changed due to a body rotation, attenuating the effect of the front but not of the rear cue. The door and object cues both appeared to define boundaries of spatial categories when they were used for reorientation. This supports the idea that both types of cues can assist in environment-centered memory formation.
    Memory & Cognition 06/2013; · 1.92 Impact Factor
  • Stephen Dopkins, Jesse Sargent, Catherine T Ngo
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    ABSTRACT: A new method was used to explore the role of perceptual information in familiarity-based recognition. The method uses a pairwise recognition task to compare recognition judgments to a test word when that word is related and unrelated to an immediately preceding word. If the false-alarm rate to the test word is greater when the two words are related, this is interpreted as reflecting an increase in the likelihood of positive familiarity assessment to the test word (Ngo, C. T., Sargent, J., & Dopkins, S. [2007]. Level of discrimination for recognition judgments reduced following the recognition of semantically related words. Journal of Memory and Language, 57, 415-436. doi:10.1016/j.jml.2007.05.007). The occurrence of such an increase for a given sort of preceding word-test word relatedness is taken as indicating that information of the sort in question is involved in familiarity-based recognition. Whereas previous work with this method has failed to find evidence that perceptual information is involved in familiarity-based recognition, the present study observed such evidence, under conditions in which previous work with other methods suggested that perceptual information would be likely to be involved in familiarity-based recognition. Thus, the study helped to validate the method and produced converging evidence that perceptual information is sometimes involved in familiarity-based recognition. The results of the study suggest that perceptual information is more likely to be involved in familiarity-based recognition when the lists for the recognition task are short. (PsycINFO Database Record (c) 2012 APA, all rights reserved).
    Canadian Journal of Experimental Psychology 10/2012; · 1.02 Impact Factor
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    Jesse Sargent, Stephen Dopkins, John Philbeck
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    ABSTRACT: This study examines bias (constant error) in spatial memory in an effort to determine whether this bias is defined by a dynamic egocentric reference frame that moves with the observer or by an environmentally fixed reference frame. Participants learned the locations of six target objects around them in a room, were blindfolded, and then rotated themselves to face particular response headings. From each response heading, participants used a pointer to indicate the remembered azimuthal locations of the objects. Analyses of the angular pointing errors showed a previously observed pattern of bias. More importantly, it appeared that this pattern of bias was defined relative to and moved with the observer--that is, was egocentric and dynamic. These results were interpreted in the framework of a modified category adjustment model as suggesting the existence of dynamic categorical (nonmetric) spatial codes.
    Psychonomic Bulletin & Review 08/2011; 18(6):1105-12. · 2.99 Impact Factor
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    Stephen Dopkins, Johanna Nordlie
    Discourse Processes - DISCOURSE PROCESS. 01/2011;
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    Stephen Dopkins, Jesse Sargent, Catherine T Ngo
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    ABSTRACT: We explored the effect of superficial priming in episodic recognition and found it to be different from the effect of semantic priming in episodic recognition. Participants made recognition judgments to pairs of items, with each pair consisting of a prime item and a test item. Correct positive responses to the test item were impeded if the prime and test item were superficially related; this was the case when the items were words and the crucial relationship was phonological and orthographic as well as when the items were letter strings and the crucial relationship was orthographic. The results of further experiments suggested that the priming effect cannot be attributed to a process of discounting or to habituation in a familiarity assessment process.
    Journal of Memory and Language 07/2010; 63(1):35-45. · 2.80 Impact Factor
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    ABSTRACT: In order to gain insight into the nature of human spatial representations, the current study examined how those representations are affected by blind rotation. Evidence was sought on the possibility that whereas certain environmental aspects may be updated independently of one another, other aspects may be grouped (or chunked) together and updated as a unit. Participants learned the locations of an array of objects around them in a room, then were blindfolded and underwent a succession of passive, whole-body rotations. After each rotation, participants pointed to remembered target locations. Targets were located more precisely relative to each other if they were (a) separated by smaller angular distances, (b) contained within the same regularly configured arrangement, or (c) corresponded to parts of a common object. A hypothesis is presented describing the roles played by egocentric and allocentric information within the spatial updating system. Results are interpreted in terms of an existing neural systems model, elaborating the model's conceptualization of how parietal (egocentric) and medial temporal (allocentric) representations interact.
    Journal of Experimental Psychology Learning Memory and Cognition 05/2010; 36(3):576-89. · 3.10 Impact Factor
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    ABSTRACT: Two experiments compared the impact of conceptual and perceptual processing at encoding on the familiarity-based recognition of items without preexisting conceptual representations. The stimuli for the experiments were visual designs and nonsense letter strings. The process dissociation procedure was used in conjunction with the process dissociation equations and the Dual Process Signal Detection model to assess the contributions of familiarity-based recognition and recollection in the recognition of the stimuli. A conceptual processing advantage was observed in both experiments: familiarity-based recognition was enhanced more by conceptual than by perceptual processing at encoding. It is suggested that the results may be problematic for the view that conceptual priming underlies the conceptual processing advantage.
    Canadian Journal of Experimental Psychology 03/2010; 64(1):67-76. · 1.02 Impact Factor
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    ABSTRACT: On each trial of the experimental procedure the participant read a list of words and made successive recognition judgements to multiple test words. The bias for a given recognition judgement was more conservative if the judgement followed a correct positive response to a target than if it followed a correct negative response to a lure. Similar results were not observed for successive semantic recognition judgements. The bias shift was greater when the study list was short than when the list was long. The results suggest that participants in a recognition task have a sense of the size of the set of targets that might possibly be presented on the next trial and that, under conditions in which a word can only be presented once during the test phase, their bias becomes more conservative after a positive response to a target because the set is depleted.
    Memory 02/2010; 18(3):272-83. · 2.09 Impact Factor
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    ABSTRACT: While an increasing number of behavioral studies examining spatial cognition use experimental paradigms involving disorientation, the process by which one becomes disoriented is not well explored. The current study examined this process using a paradigm in which participants were blindfolded and underwent a succession of 70 degrees or 200 degrees passive, whole body rotations around a fixed vertical axis. After each rotation, participants used a pointer to indicate either their heading at the start of the most recent turn or their heading at the start of the current series of turns. Analyses showed that in both cases, mean pointing errors increased gradually over successive turns. In addition to the gradual loss of orientation indicated by this increase, analysis of the pointing errors also showed evidence of occasional, abrupt loss orientation. Results indicate multiple routes from an oriented to a disoriented state, and shed light on the process of becoming disoriented.
    Acta psychologica 09/2008; 129(2):234-42. · 2.19 Impact Factor
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    ABSTRACT: Previous studies have demonstrated large errors (over 30 degrees ) in visually perceived exocentric directions (the direction between two objects that are both displaced from the observer's location; e.g., Philbeck et al. [Philbeck, J. W., Sargent, J., Arthur, J. C., & Dopkins, S. (2008). Large manual pointing errors, but accurate verbal reports, for indications of target azimuth. Perception, 37, 511-534]). Here, we investigated whether a similar pattern occurs in auditory space. Blindfolded participants either attempted to aim a pointer at auditory targets (an exocentric task) or gave a verbal estimate of the egocentric target azimuth. Targets were located at 20-160 degrees azimuth in the right hemispace. For comparison, we also collected pointing and verbal judgments for visual targets. We found that exocentric pointing responses exhibited sizeable undershooting errors, for both auditory and visual targets, that tended to become more strongly negative as azimuth increased (up to -19 degrees for visual targets at 160 degrees ). Verbal estimates of the auditory and visual target azimuths, however, showed a dramatically different pattern, with relatively small overestimations of azimuths in the rear hemispace. At least some of the differences between verbal and pointing responses appear to be due to the frames of reference underlying the responses; when participants used the pointer to reproduce the egocentric target azimuth rather than the exocentric target direction relative to the pointer, the pattern of pointing errors more closely resembled that seen in verbal reports. These results show that there are similar distortions in perceiving exocentric directions in visual and auditory space.
    Acta Psychologica 06/2008; 129(1):72-82. · 2.26 Impact Factor
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    ABSTRACT: Human spatial representations of object locations in a room-sized environment were probed for evidence that the object locations were encoded relative not just to the observer (egocentrically) but also to each other (allocentrically). Participants learned the locations of 4 objects and then were blindfolded and either (a) underwent a succession of 70 degrees and 200 degrees whole-body rotations or (b) were fully disoriented and then underwent a similar sequence of 70 degrees and 200 degrees rotations. After each rotation, participants pointed to the objects without vision. Analyses of the pointing errors suggest that as participants lost orientation, represented object directions generally "drifted" off of their true directions as an ensemble, not in random, unrelated directions. This is interpreted as evidence that object-to-object (allocentric) relationships play a large part in the human spatial updating system. However, there was also some evidence that represented object directions occasionally drifted off of their true directions independently of one another, suggesting a lack of allocentric influence. Implications regarding the interplay of egocentric and allocentric information are considered.
    Journal of Experimental Psychology Learning Memory and Cognition 06/2008; 34(3):602-15. · 3.10 Impact Factor
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    Stephen Dopkins, Jesse Sargent
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    ABSTRACT: Pairs of words are identified more quickly as coming from different sentences the further apart the words are in the network representation of their native text. How is the distance between the words measured? According to the network connection hypothesis, the distance between 2 words is the length of the network path between the propositions to which they belong, as measured by a process of spreading activation. According to the location code hypothesis, the distance between 2 words is the difference between codes that record the locations of their propositions in the network representation. The results of 3 experiments supported the network connection hypothesis.
    The American Journal of Psychology 02/2008; 121(2):273-92. · 1.09 Impact Factor
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    Catherine T Ngo, Jesse Sargent, Stephen Dopkins
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    ABSTRACT: Participants read lists of words and then made recognition judgments to pairs of words, each of which consisted of a prime word and a test word. At issue was the effect of a semantic relationship between the prime word and the test word on the recognition judgment to the test word. Under standard recognition conditions, semantic priming impeded correct recognition judgments to new test words and had no effect on recognition judgments to old test words. The overall effect was to reduce the level of discrimination for recognition judgments to the test word. Under conditions in which familiarity assessment would be expected to play a greater role in judgments to old test words, semantic priming facilitated those judgments. The results are explained in terms of a dual process account of recognition.
    Journal of Memory and Language 11/2007; 57(3):415-436. · 2.80 Impact Factor
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    ABSTRACT: The present study sought a clearer understanding of spatial memory function consequent to temporal lobe resection, and, in particular, of spatial memory function with respect to two- as well as three-dimensional frames of reference. Relative to a group of 15 control participants, a group of 15 epilepsy patients with right temporal resections demonstrated deficits of memory for locations in a two-dimensional display. A group of 13 epilepsy patients with left temporal resections did not demonstrate such deficits. The right and the left resection groups both demonstrated deficits of memory for item-location relationships in a two-dimensional display. The right but not the left resection group demonstrated deficits of memory for item-location relationships in a three-dimensional display. The differing results that were observed for item-location relationships in two- and three-dimensional displays were attributed to differences in the way item information is bound with location information concerning two- and three-dimensional domains.
    Journal of Clinical and Experimental Neuropsychology 12/2006; 28(8):1462-81. · 2.16 Impact Factor
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    ABSTRACT: Four experiments were performed to explore a recognition decrement that is associated with the recognition of a word from a short list. The stimulus material for demonstrating the phenomenon was a list of words of different syntactic types. A word from the list was recognized less well following a decision that a word of the same type had occurred in the list than following a decision that such a word had not occurred in the list. A recognition decrement did not occur for a word of a given type following a positive recognition decision to a word of a different type. A recognition decrement did not occur when the list consisted exclusively of nouns. It was concluded that the phenomenon may reflect a criterion shift but, probably, does not reflect a list strength effect, suppression, or familiarity attribution consequent to a perceived discrepancy between actual and expected fluency.
    Memory & Cognition 07/2006; 34(4):839-53. · 1.92 Impact Factor
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    Stephen Dopkins, Catherine Trinh Ngo
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    ABSTRACT: In studies of anaphor comprehension, the capacity for recognizing a noun in a sentence decreases following the resolution of a repeated-noun anaphor (Gernsbacher, 1989). In studies of recognition memory, the capacity for recognizing a noun in a scrambled sentence decreases following the recognition that another noun has occurred before in the scrambled sentence (Dopkins & Ngo, 2002). The results of the present study suggest that these two phenomena reflect the same recognition memory process. The results suggest further that this is not because participants in studies of anaphor comprehension ignore the discourse properties of the stimulus materials and treat them as lists of words upon which memory tests are to be given. These results suggest that recognition processes play a role in anaphor comprehension and that such processes are in part the means by which repeated-noun anaphors are identified as such.
    Journal of Memory and Language 08/2005; 53(2):186-203. · 2.80 Impact Factor
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    Stephen Dopkins
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    ABSTRACT: On each trial of the primary task for the study, a pair of small circles appeared on a computer screen. Across trials, the circles appeared in an array of positions on the screen. The participant was required on each trial to indicate whether or not the test circles were two or fewer position units apart in terms of the horizontal dimension of this array. The discrimination that the task required was easier to the extent that the vertical distance between the circles was ignored. When the task was performed under a high degree of speed stress, vertical distance and horizontal distance exerted equivalent effects on measures of performance. When the task was performed under a lesser degree of speed stress, horizontal distance exerted a larger effect than vertical distance did. The results supported the early holistic hypothesis over the dimensional similarity hypothesis as an account of the way information from different dimensions is accessed in perceptual processing.
    Perception & Psychophysics 05/2005; 67(3):513-30. · 1.37 Impact Factor
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    ABSTRACT: The results of 2 experiments support the contention that patients with Alzheimer's disease (AD) show a relative loss of the semantic features that distinguish concepts from one another and that the representations of pairs of concepts consequently share a larger proportion of their associated features in AD than in normal aging. In Experiment 1, AD patients listed fewer features for a set of concepts than did healthy older adults and were more deficient at listing features if the features were distinctive to particular concepts than if they were shared by multiple concepts. In Experiment 2, AD patients showed online priming at levels of relatedness at which healthy older adults did not.
    Neuropsychology 11/2004; 18(4):603-12. · 3.58 Impact Factor

Publication Stats

137 Citations
83.11 Total Impact Points

Institutions

  • 2014
    • The Psychonomic Society
      Society Hill, New Jersey, United States
  • 1993–2011
    • George Washington University
      • Department of Psychology
      Washington, Washington, D.C., United States
  • 2010
    • Baylor College of Medicine
      Houston, Texas, United States
  • 1990
    • University of Massachusetts Amherst
      • Department of Psychology
      Amherst Center, MA, United States
  • 1988
    • Montefiore Medical Center
      New York City, New York, United States
    • Columbia University
      New York City, New York, United States