The GANE (glutamate amplifies noradrenergic effects) model proposed by Mather et al. attempts to explain how norepinephrine enhances processing in highly activated brain regions. Careful perusal of the sparse data available from recording studies in animals reveals that noradrenergic neurons are excited mainly by any change in the environment – a salient, novel, or unexpected sensory stimulus or a change in behavioral contingencies. This begets the “network reset hypothesis” supporting the notion that norepinephrine promotes rapid cognitive and behavioral adaption

Emotional events can either impair or enhance memory for immediately preceding items. The GANE model explains this bidirectional effect as a glutamate “priority” signal that modulates noradrenaline release depending on arousal state. We argue for an alternative explanation: that priority itself evokes phasic noradrenaline release. Thus, contrasting E-1 memory effects are explained by a mechanism based on the Bienenstock–Cooper–Munro theory.

The time scale of the effects of emotional arousal on neutral information processing is crucial for the predictions of the glutamate amplifies noradrenergic effects (GANE) model. GANE suggests that when emotional and neutral stimuli are presented in a sequence, neutral information processing will change. We review the literature on event-related potentials, including our own data set, to test this prediction.

In this commentary we focus on individual differences in proposed mechanisms underlying arousal-based enhancement of prioritized stimuli. We discuss the potential of genotyping studies for examining effects of noradrenergic processes on stimulus prioritization in humans and stress the importance of potential individual differences in the activity of specific receptor subtypes in hotspot processes proposed by the GANE model.

We draw attention to studies indicating that phasic arousal increases interference effects in tasks necessitating the recruitment of cognitive control. We suggest that arousal-biased competition models such as GANE (glutamate amplifies noradrenergic effects) may be able to explain these findings by taking into account dynamic, within-trial changes in the relative salience of task-relevant and task-irrelevant features. However, testing this hypothesis requires a computational model.

The GANE (glutamate amplifies noradrenergic effects) model proposes that local glutamate–norepinephrine interactions enable “winner-take-more” effects in perception and memory under arousal. A diverse range of commentaries addressed both the nature of this “hotspot” feedback mechanism and its implications in a variety of psychological domains, inspiring exciting avenues for future research.

What determines what we see? In contrast to the traditional “modular” understanding of perception, according to which visual processing is encapsulated from higher-level cognition, a tidal wave of recent research alleges that states such as beliefs, desires, emotions, motivations, intentions, and linguistic representations exert direct, top-down influences on what we see. There is a growing consensus that such effects are ubiquitous, and that the distinction between perception and cognition may itself be unsustainable. We argue otherwise: None of these hundreds of studies – either individually or collectively – provides compelling evidence for true top-down effects on perception, or “cognitive penetrability.” In particular, and despite their variety, we suggest that these studies all fall prey to only a handful of pitfalls. And whereas abstract theoretical challenges have failed to resolve this debate in the past, our presentation of these pitfalls is empirically anchored: In each case, we show not only how certain studies could be susceptible to the pitfall (in principle), but also how several alleged top-down effects actually are explained by the pitfall (in practice). Moreover, these pitfalls are perfectly general, with each applying to dozens of other top-down effects. We conclude by extracting the lessons provided by these pitfalls into a checklist that future work could use to convincingly demonstrate top-down effects on visual perception. The discovery of substantive top-down effects of cognition on perception would revolutionize our understanding of how the mind is organized; but without addressing these pitfalls, no such empirical report will license such exciting conclusions.

Firestone & Scholl's (F&S's) techniques to combat task demand by manipulating expectations and offering alternative cover stories are fundamentally flawed because they introduce new forms of demand. We review five superior techniques to mitigate demand used in confirmatory studies of top-down effects. We encourage researchers to apply the same standards when evaluating evidence on both sides of the debate.

Although the authors do a valuable service by elucidating the pitfalls of inferring top-down effects, they overreach by claiming that vision is cognitively impenetrable. Their argument, and the entire question of cognitive penetrability, seems rooted in a discrete, stage-like model of the mind that is unsupported by neural data.

One approach to the issue of a joint in nature between perception and cognition is to investigate whether the concepts of perception and cognition can be tweaked to avoid direct, content-specific effects of cognition on perception.

We challenge Firestone & Scholl's (F&S's) narrow conceptualization of what perception is and – most important – what it is for. Perception guides our (inter)actions with the environment, with attention ensuring that the actor is attuned to information relevant for action. We dispute F&S's misconceived (and counterfactual) view of perception as a module that functions independently from cognition, attention, and action.

Firestone & Scholl (F&S) bracket many attentional effects as “peripheral,” altering the inputs to a cognitive process without altering the processing itself. By way of contrast, I highlight an emerging class of neurocomputational models that imply profound, pervasive, nonperipheral influences of attention on perception. This transforms the landscape for empirical debates concerning possible top-down effects on perception.

Firestone & Scholl (F&S) assume that pure perception is unaffected by cognition. This assumption is untenable for definitional, anatomical, and empirical reasons. They discount research showing nonoptical influences on visual perception, pointing out possible methodological “pitfalls.” Results generated in multiple labs are immune to these “pitfalls,” suggesting that perceptions of physical layout do indeed reflect bioenergetic resources.

Not only can the pitfalls that Firestone & Scholl (F&S) identify be generalised across multiple studies within the field of visual perception, but also they have general application outside the field wherever perceptual and cognitive processing are compared. We call attention to the widespread susceptibility of research on the perception of speech to versions of the same pitfalls.

Firestone & Scholl (F&S) postulate that vision proceeds without any direct interference from cognition. We argue that this view is extreme and not in line with the available evidence. Specifically, we discuss two well-established counterexamples: Attention directly affects core aspects of visual processing, and multisensory modulations of vision originate on multiple levels, some of which are unlikely to fall “within perception.”

In this commentary on Firestone & Scholl's (F&S's) article, we argue that researchers should use brain-activity modelling to investigate top-down mechanisms. Using functional brain imaging and a specific cognitive paradigm, modelling the BOLD signal provided new insight into the dynamic causalities involved in the influence of cognitions on perceptions.

I review experiments in which drinking a sugarless drink causes some participants who have low blood sugar from fasting to give lower slant estimates. Ironically, this only occurs to the extent that they believe that they have received sugar and that the sugar was meant to make the hill look shallower; those who received sugar showed no similar effect. These findings support the hypothesis that low blood sugar causes greater participant cooperation – which, in combination with other experimental details, can lead participants to make judgments that can either seem to support the effort hypothesis or contradict it. I also emphasize the importance of perceptual stability in the perception of spatial layout.

Firestone & Scholl (F&S) assert that perceptual learning is not a top-down effect, because experience-mediated changes arise from familiarity with the features of the object through simple repetition and not knowledge about the environment. Emberson and Amso (2012) provide a clear example of perceptual learning that bypasses the authors' “pitfalls” and in which knowledge, not repeated experience, results in changes in perception.

The brain has evolved in this multisensory context to perceive the world in an integrated fashion. Although there are good reasons to be skeptical of the influence of cognition on perception, here we argue that the study of sensory substitution devices might reveal that perception and cognition are not necessarily distinct, but rather continuous aspects of our information processing capacities.

We introduce two propositions for understanding top-down effects on perception. First, perception is not a unitary construct but is composed of multiple components. Second, behavior is multiply determined by cognitive processes. We call for a process-oriented research approach to perception and use our own research on moral perception as a “case study of case studies” to examine these issues.