Profiles

Anders Sand

Vik. universitetslektor

Visa sidan på svenska
Works at Department of Psychology
Telephone 08-16 48 04
Email anders.sand@psychology.su.se
Visiting address Frescati hagväg 9A
Room 213
Postal address Psykologiska institutionen 106 91 Stockholm

Publications

A selection from Stockholm University publication database
  • Anders Sand, Mats E. Nilsson.

    Is semantic priming driven by the objective or perceived meaning of the priming stimulus? This question is relevant as many studies suggest that the objective meaning of invisible stimuli can influence cognitive processes and behavior. In an experiment involving 66 participants, we tested whether the perceived meaning of misperceived stimuli may influence response times. Stroop priming, i.e., longer response times for incongruent versus congruent prime–target pairs, was observed in trials in which the prime was correctly identified. However, reversed Stroop priming was observed when the prime stimulus was incorrectly identified. Even in trials in which participants reported “no” prime percept and identified the primes at close to chance level (i.e., fulfilling both a subjective and objective definition of “subliminal”), Stroop priming corresponded to perceived, not objective, congruency. Under conditions traditionally claimed to be “subliminal,” this allows occasional weak percepts and mispercepts to be intermixed with no percepts.

  • 2016. Anders Sand. Frontiers in Psychology 7

    A new paradigm for investigating whether a cognitive process is independent of perception was recently suggested. In the paradigm, primes are shown at an intermediate signal strength that leads to trial-to-trial and inter-individual variability in prime perception. Here, I used this paradigm and an objective measure of perception to assess the influence of prime identification responses on Stroop priming. I found that sensory states producing correct and incorrect prime identification responses were also associated with qualitatively different priming effects. Incorrect prime identification responses were associated with reversed priming effects but in contrast to previous studies, I interpret this to result from the (mis-)perception of primes rather than from a subliminal process. Furthermore, the intermediate signal strength also produced inter-individual variability in prime perception that strongly influenced priming effects: only participants who on average perceived the primes were Stroop primed. I discuss how this new paradigm, with a wide range of d′ values, is more appropriate when regression analysis on inter-individual identification performance is used to investigate perception-dependent processing. The results of this study, in line with previous results, suggest that drawing conclusions about subliminal processes based on data averaged over individuals may be unwarranted.

  • Thesis (Doc) Subliminal or not?
    2016. Anders Sand (et al.).

    Stimuli that cannot be perceived (i.e., that are subliminal) can still elicit neural responses in an observer, but can such stimuli influence behavior and higher-order cognition? Empirical evidence for such effects has periodically been accepted and rejected over the last six decades. Today, many psychologists seem to consider such effects well-established and recent studies have extended the power of subliminal processing to new limits. In this thesis, I examine whether this shift in zeitgeist is matched by a shift in evidential strength for the phenomenon.

    This thesis consists of three empirical studies involving more than 250 participants, a simulation study, and a quantitative review. The conclusion based on these efforts is that several methodological, statistical, and theoretical issues remain in studies of subliminal processing. These issues mean that claimed subliminal effects might be caused by occasional or weak percepts (given the experimenters’ own definitions of perception) and that it is still unclear what evidence there is for the cognitive processing of subliminal stimuli. New data are presented suggesting that even in conditions traditionally claimed as “subliminal”, occasional or weak percepts may in fact influence cognitive processing more strongly than do the physical stimuli, possibly leading to reversed priming effects. I also summarize and provide methodological, statistical, and theoretical recommendations that could benefit future research aspiring to provide solid evidence for subliminal cognitive processing.

  • 2016. Anders Sand, Mats E. Nilsson. Consciousness and Cognition 44, 29-40

    A difficulty for reports of subliminal priming is demonstrating that participants who actually perceived the prime are not driving the priming effects. There are two conventional methods for testing this. One is to test whether a direct measure of stimulus perception is not significantly above chance on a group level. The other is to use regression to test if an indirect measure of stimulus processing is significantly above zero when the direct measure is at chance. Here we simulated samples in which we assumed that only participants who perceived the primes were primed by it. Conventional analyses applied to these samples had a very large error rate of falsely supporting subliminal priming. Calculating a Bayes factor for the samples very seldom falsely supported subliminal priming. We conclude that conventional tests are not reliable diagnostics of subliminal priming. Instead, we recommend that experimenters calculate a Bayes factor when investigating subliminal priming.

  • 2014. Anders Sand, Mats E. Nilsson. Experimental Brain Research 232 (6), 1707-1716

    Learning in perceptual tasks is typically highly specific to the trained stimulus parameters. However, can learning be specific to a stimulus parameter that is perceptually indistinguishable from another? We assessed this question using a perceived sound location task in which the perceived sound location was created through either an interaural time difference (ITD) cue or an interaural level difference (ILD) cue. We used the same transient, broadband sound (clicks) for both cues, and after training on one of the cues, listeners switched cue mid-session. This allowed us to assess cue specificity or transfer when the subjectively unnoticed cue switch occurred. One group of listeners improved their ITD performance as a function of training, but deteriorated in performance when switching to ILD in mid training session. Another group of listeners started with ILD training; their improved performance level did not deteriorate as they switched to the ITD cue. This transfer asymmetry was not hypothesized, and we therefore extended our study with a second data collection. Both the training effect and the transfer asymmetry remained after the second data collection. Our results indicate (a) listeners can improve both their ITD and ILD performance for click sounds, extending previous findings on tones; (b) learning can be specific to a stimulus parameter that is indistinguishable from another, as ITD learning did not transfer to ILD performance; but (c) ILD learning can transfer to ITD performance. This transfer asymmetry may have occurred because of how ITD and ILD are coded in early brainstem areas.

Show all publications by Anders Sand at Stockholm University

Last updated: February 23, 2018

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