The Predation Game: Does dividing attention affect patterns of human foraging?

Attention is known to play an important role in shaping the behaviour of both human and animal foragers. Here, in two experiments, we built on our previous interactive tasks to create an online foraging game for studying divided attention in human participants exposed to the (simulated) risk of predation. Participants used a “sheep” object to collect items from different target categories randomly distributed across the display. Each trial also contained “wolf” objects, whose movement was inspired by classic studies of multiple object tracking. For “hunted” participants, collision with any wolf terminated the trial, making the need to monitor and avoid the predators crucial to success. For “distracted” participants, the wolf objects did not interact with the sheep, and could effectively be ignored. In Experiment 1, we used an established Feature/Conjunction manipulation to vary the difficulty of target selection. In Experiment 2, we varied the value and the prevalence of target items to examine potential trade-offs between risk and reward. In both experiments, we found very clear differences between the foraging patterns of hunted versus distracted participants. We were also able to replicate basic foraging patterns associated with target complexity and reward, respectively. Unexpectedly, hunted participants did not show a tendency to restricting their search to a single category, the hallmark of attention limited foraging. Rather, they were more likely to select from all available categories, compared to the distracted participants. Such behaviour is consistent with the idea that risk of predation in our task modulated levels of alertness/arousal, counteracting the costs of having to both select targets and monitor for wolves. While the effects of phasic changes in alertness and arousal are well captured in standard capacity models of attention and are also central to recent attempts to explain individual differences in human performance they do not as yet play a major role in the attention models applied to either human or animal foraging.

On the role of conjunction in adjective ordering preferences

Adjective ordering preferences are robustly attested in English and many unrelated languages. In nominals with multi-adjective strings (e.g., big blue box), chances are the order of the adjectives is non-arbitrary. However, ordering preferences are claimed to neutralize in cases where multi-adjective strings are formed via conjunction (e.g., blue and big box). We provide empirical evidence in support of this claim, but with an important caveat: conjunction neutralizes adjective ordering preferences in languages like Spanish where multi-adjective strings obligatorily feature conjunction. In English, where multi-adjective strings optionally feature conjunction, ordering preferences persist in the presence of conjunction.

A serious game to explore human foraging in a 3D environment

Traditional search tasks have taught us much about vision and attention. Recently, several groups have begun to use multiple-target search to explore more complex and temporally extended “foraging” behaviour. Many of these new foraging tasks, however, maintain the simplified 2D displays and response demands associated with traditional, single-target visual search. In this respect, they may fail to capture important aspects of real-world search or foraging behaviour. In the current paper, we present a serious game for mobile platforms in which human participants play the role of an animal foraging for food in a simulated 3D environment. Game settings can be adjusted, so that, for example, custom target and distractor items can be uploaded, and task parameters, such as the number of target categories or target/distractor ratio are all easy to modify. We demonstrate how the app can be used to address specific research questions by conducting two human foraging experiments. Our results indicate that in this 3D environment, a standard feature/conjunction manipulation does not lead to a reduction in foraging runs, as it is known to do in simple, 2D foraging tasks. Differences in foraging behaviour are discussed in terms of environment structure, task demands and attentional constraints.

Facial Recall: Feature–Conjunction Effects in Source Retrieval Versus Item Recognition

Within memory processing, feature and conjunction effects refer to higher false alarms (incorrectly naming items as previously seen) for stimuli with partial/all features taken from different previously studied versus novel items. In this study, we compared feature–conjunction effects in the memory tasks of both item recognition and source retrieval, using faces as stimuli. We found greater feature–conjunction effects on source retrieval versus item recognition tasks, though participants gave slower responses on source retrieval versus item recognition. Thus, our data were consistent with dual-process memory theory in which familiarity contributes to high false alarms in compound faces even while feature–conjunction effects enhance recollection in source retrieval.

An auditory illusion reveals the role of streaming in the temporal misallocation of perceptual objects

This study investigates the neural correlates and processes underlying the ambiguous percept produced by a stimulus similar to Deutsch's ‘octave illusion’, in which each ear is presented with a sequence of alternating pure tones of low and high frequencies. The same sequence is presented to each ear, but in opposite phase, such that the left and right ears receive a high–low–high … and a low–high–low … pattern, respectively. Listeners generally report hearing the illusion of an alternating pattern of low and high tones, with all the low tones lateralized to one side and all the high tones lateralized to the other side. The current explanation of the illusion is that it reflects an illusory feature conjunction of pitch and perceived location. Using psychophysics and electroencephalogram measures, we test this and an alternative hypothesis involving synchronous and sequential stream segregation, and investigate potential neural correlates of the illusion. We find that the illusion of alternating tones arises from the synchronous tone pairs across ears rather than sequential tones in one ear, suggesting that the illusion involves a misattribution of time across perceptual streams, rather than a misattribution of location within a stream. The results provide new insights into the mechanisms of binaural streaming and synchronous sound segregation. This article is part of the themed issue ‘Auditory and visual scene analysis’.