Steven P. Tipper

The Negative Priming Effect: Inhibitory Priming by Ignored Objects

A priming paradigm was employed to investigate the processing of an ignored object during selection of an attended object. Two issues were investigated: the level of internal representation achieved for the ignored object, and the subsequent fate of this representation. In Experiment 1 a prime display containing two superimposed objects was briefly presented. One second later a probe display was presented containing an object to be named. If the ignored object in the prime display was the same as the subsequent probe, naming latencies were impaired. This effect is termed negative priming. It suggests that internal representations of the ignored object may become associated with inhibition during selection. Thus, selection of a subsequent probe object requiring these inhibited representations is delayed. Experiment 2 replicated the negative priming effect with a shorter inter-stimulus interval. Experiment 3 examined the priming effects of both the ignored and the selected objects. The effect of both identity repetition and a categorical relationship between prime and probe stimuli were investigated. The data showed that for a stimulus selected from the prime display, naming of the same object in the probe display was facilitated. When the same stimulus was ignored in the prime display, however, naming of it in the probe display was again impaired (negative priming). That negative priming was also demonstrated with categorically related objects suggests that ignored objects achieve categorical levels of representation, and that the inhibition may be at this level.

Gaze cueing of attention : Visual attention, social cognition, and individual differences

During social interactions, peoples eyes convey a wealth of information about their direction of attention and their emotional and mental states. This review aims to provide a comprehensive overview of past and current research into the perception of gaze behavior and its effect on the observer. This encompasses the perception of gaze direction and its influence on perception of the other person, as well as gaze-following behavior such as joint attention, in infant, adult, and clinical populations. Particular focus is given to the gaze-cueing paradigm that has been used to investigate the mechanisms of joint attention. The contribution of this paradigm has been significant and will likely continue to advance knowledge across diverse fields within psychology and neuroscience.

Does negative priming reflect inhibitory mechanisms? A review and integration of conflicting views.

Negative priming has traditionally been viewed as a reflection of an inhibitory mechanism of attention. However, recent accounts have suggested that negative priming does not reflect inhibitory mechanisms. Rather, slowed reaction times on negative priming trials are either due to retrieval of incompatible response tags or of mismatching perceptual information, or due to extra processes needed to distinguish past from present information. In contrast, it is proposed that there is no firm evidence to discount inhibition models. In fact, although retrieval processes can be implicated in negative priming effects, understanding of these requires consideration of the inhibitory processes involved in selecting information for goal-directed behaviour.

Selective attention and priming: Inhibitory and facilitatory effects of ignored primes

The priming effects of ignored information have been studied in Stroop displays (Neill, 1977) and with spatially superimposed drawings (Tipper, in this issue); naming of probes related to ignored primes is delayed in these experiments (“negative priming”). This negative priming effect is confirmed in a list reading task in Experiment 1, which used partially superimposed letters, and Experiment 2, which used spatially separated letters. Furthermore, Lowe (1979) using Stroop colour words observed that changing the nature of the probe such that it did not require selection from a competing word reversed the priming effects of the ignored word from inhibition to facilitation. Experiment 3 confirmed this observation when subjects selected a red letter from a green letter. Two models are suggested to account for this result. In the first, negative priming is a product of the ignored prime and subsequent probe being encoded both as a stimulus to be ignored and one to be named (Allport, Tipper and Chmiel, in press; Lowe, in press). This dual encoding is ambiguous, requiring further processing before response can be output. The other model suggests that negative priming reflects inhibition of response to ignored information, slowing naming latencies to probe stimuli that require the same response. Experiment 4 attempts to differentiate between the models, and the latter inhibition view is preferred.

Selective reaching: evidence for action-centered attention

Most studies of selective attention briefly present static 2-dimensional stimuli and require arbitrary responses such as verbal naming or a keypress. Many of our perceptual-motor interactions with the environment, however, require reaching directly toward an object while ignoring other objects in the scene. A series of experiments examines selective attention in the latter reaching situation. Effects previously observed in the traditional experimental procedures were obtained, suggesting that the models developed (which propose inhibitory mechanisms, e.g.) apply to ecologically valid situations. Attention accesses action-centered internal representations during such tasks.

Object-based and environment-based inhibition of return of visual attention.

Efficient search for an object often requires that attention be prevented from returning to recently examined environmental loci. M. I. Posner and Y. A. Cohen (1984) proposed that inhibition of return (IOR) of visual attention is a search mechanism that prevents such attentional perservation. The internal representations upon which IOR functions were examined and the following conclusions were drawn: First, IOR mechanisms have access to both object- and environment-based representations. Second, environment-based inhibition can be associated with a featureless environmental location, whereas the object-based mechanism requires that attention be oriented to a visible object. These findings are discussed in terms of physiological pathways that may mediate location- and object-based effects.

Selective Reaching to Grasp: Evidence for Distractor Interference Effects

Transport and grasp kinematics were examined in a task in which subjects selectively reached to grasp a target object in the presence of non-target objects. In a variety of experiments significant interference effects were observed in temporal parameters, such as movement time, and spatial parameters, such as path. In general, the presence of non-targets slowed down the reach. Furthermore, reach paths were affected such that the hand veered away from near non-targets in reaches for far targets, even though the non-targets were not physical obstacles to the reaching hand. In contrast, the hand veered towards far non-targets in near reaches. We conclude that non-targets evoke competing responses, and the inhibitory mechanisms that resolve this competition are revealed in the reach path.

Negative priming between pictures and words in a selective attention task: Evidence for semantic processing of ignored stimuli

This study examined the processing of ignored pictures and words when attention was directed to a different picture or word. Previous work by Tipper (1985) demonstrated that the priming effect of an ignored picture on a subsequent categorically related picture is inhibitory. This effect was termednegative priming. Tipper concluded that ignored pictures achieved abstract categorical levels of internal representation, and that these representations were inhibited during selection of a simultaneously presented picture. This conclusion, however, was premature. Observation of the figures used by Tipper suggests that objects within a category have greater structural similarity than do objects in different categories. The negative priming effect could therefore be at a structural level of representation. The present study examined priming across symbolic domains (pictures and words) where there was no structural relationship between objects. Negative priming was again observed and was equivalent to the negative priming observed within symbolic domain. These data suggest that ignored drawings and words do achieve abstract categorical levels of representation, and that the mechanisms underlying negative priming operate at, or beyond, this level.

Selection of moving and static objects for the control of spatially directed action

Research studying visual selective attention has largely examined filtering tasks in which stationary targets are selected from stationary distractors by a physical cue such as location and identity is the reported attribute. During many interactions with the visual environment however, target stimuli are selected by what they are, whereas action is controlled by where the stimulus is located. This study demonstrates that the interference and negative priming effects observed in standard filtering tasks, which suggest that distractors are analyzed and subsequently inhibited during selection, are also observed when targets are selected on the basis of identity and spatial location is the reported attribute. Furthermore, experimental results suggest that inhibition associated with distracting objects in this new task is object-centered, so that if the object is moving through space, inhibition moves with it.

Sex differences in eye gaze and symbolic cueing of attention

Observing a face with averted eyes results in a reflexive shift of attention to the gazed-at location. Here we present results that show that this effect is weaker in males than in females (Experiment 1). This result is predicted by the ‘extreme male brain’ theory of autism (Baron-Cohen, 2003), which suggests that males in the normal population should display more autism-like traits than females (e.g., poor joint attention). Indeed, participants′ scores on the Autism-Spectrum Quotient (Baron-Cohen, Wheelwright, Stott, Bolton, & Goodyear, 2001) negatively correlated with cueing magnitude. Furthermore, exogenous orienting did not differ between the sexes in two peripheral cueing experiments (Experiments 2a and 2b). However, a final experiment showed that using non-predictive arrows instead of eyes as a central cue also revealed a large gender difference. This demonstrates that reduced orienting from central cues in males generalizes beyond gaze cues. These results show that while peripheral cueing is equivalent in the male and female brains, the attention systems of the two sexes treat noninformative symbolic cues very differently.