Paradoxical choice and the reinforcing value of information

Abstract

Signals that reduce uncertainty can be valuable because well-informed decision-makers can better align their preferences to opportunities. However, some birds and mammals display an appetite for informative signals that cannot be used to increase returns. We explore the role that reward-predictive stimuli have in fostering such preferences, aiming at distinguishing between two putative underlying mechanisms. The ‘information hypothesis’ proposes that reducing uncertainty is reinforcing per se, somewhat consistently with the concept of curiosity: a motivation to know in the absence of tractable extrinsic benefits. In contrast, the ‘conditioned reinforcement hypothesis’, an associative account, proposes asymmetries in secondarily acquired reinforcement: post-choice stimuli announcing forthcoming rewards (S+) reinforce responses more than stimuli signalling no rewards (S) inhibit responses. In three treatments, rats faced two equally profitable options delivering food probabilistically after a fixed delay. In the informative option (Info), food or no food was signalled immediately after choice, whereas in the non-informative option (NoInfo) outcomes were uncertain until the delay lapsed. Subjects preferred Info when (1) both outcomes were explicitly signalled by salient auditory cues, (2) only forthcoming food delivery was explicitly signalled, and (3) only the absence of forthcoming reward was explicitly signalled. Acquisition was slower in (3), when food was not explicitly signalled, showing that signals for positive outcomes have a greater influence on the development of preference than signals for negative ones. Our results are consistent with an elaborated conditioned reinforcement account, and with the conjecture that both uncertainty reduction and conditioned reinforcement jointly act to generate preference.

A tool to act blind? Object-assisted eye-covering as a self-handicapping behavior and social play signal in Balinese long-tailed macaques

Abstract

Self-handicapping behaviors evolved as honest signals that reliably reflect the quality of their performers. In playful activities, self-handicapping is described as intentionally and unnecessarily putting oneself into disadvantageous positions and situations. Self-handicapping during play may allow individuals to learn to cope with unexpected events by improving sensori-motor coordination, as well as function as a play solicitation signal. One such self-handicapping behavior involves moving about while deliberately covering one’s eyes. We conducted a quantitative study of object-assisted eye-covering (OAEC) in a population of free-ranging Balinese macaques. After evaluating the frequency, form, distribution, and context of OAEC, we measured the responses this behavior elicited (1) in the performers with a focus on sensori-motor self-handicapping, and (2) in their conspecifics, with an emphasis on whether, and if so how, OAEC may facilitate social play. Our data provided some support for several hypotheses: OAEC is a sensori-motor self-handicapping behavior, an attention-getting cue, a social play signal, and a socially self-handicapping tactic during social play. We discuss our results from the perspective of tool-assisted self-handicapping behavior, propose a scenario to account for the emergence of this behavioral innovation, and speculate on the cultural nature of OAEC.

Discrimination of cat-directed speech from human-directed speech in a population of indoor companion cats (Felis catus)

Abstract

In contemporary western cultures, most humans talk to their pet companions. Speech register addressed to companion animals shares common features with speech addressed to young children, which are distinct from the typical adult-directed speech (ADS). The way dogs respond to dog-directed speech (DDS) has raised scientists’ interest. In contrast, much less is known about how cats perceive and respond to cat-directed speech (CDS). The primary aim of this study was to evaluate whether cats are more responsive to CDS than ADS. Secondarily, we seek to examine if the cats’ responses to human vocal stimuli would differ when it was elicited by their owner or by a stranger. We performed playback experiments and tested a cohort of 16 companion cats in a habituation–dishabituation paradigm, which allows for the measurement of subjects’ reactions without extensive training. Here, we report new findings that cats can discriminate speech specifically addressed to them from speech addressed to adult humans, when sentences are uttered by their owners. When hearing sentences uttered by strangers, cats did not appear to discriminate between ADS and CDS. These findings bring a new dimension to the consideration of human–cat relationship, as they imply the development of a particular communication into human–cat dyads, that relies upon experience. We discuss these new findings in the light of recent literature investigating cats’ sociocognitive abilities and human–cat attachment. Our results highlight the importance of one-to-one relationships for cats, reinforcing recent literature regarding the ability for cats and humans to form strong bonds.

Fruit scent as an indicator of ripeness status in ‘bat fruits’ to attract ‘fruit bats’: chemical basis of chiropterochory

Abstract

In the tropics, animal-mediated seed dispersal is the most frequently occurring dispersal syndrome, which includes traits that aid in attracting both diurnal and nocturnal dispersers. However, some plants bear fruits with special traits that make them less conspicuous to diurnal frugivores to make them exclusively available to nocturnal frugivores such as bats, which are called ‘bat fruits’. Since these fruits remain drab green in colour throughout their phases of ontogeny, the difference in scent compounds is predicted to help bats to assess their ripeness status. In this study, we specifically examined the behavioural repertoires associated with fruit removal such as ‘search latency’ and ‘number of attempts’ taken by two small-sized fruit bats (Cynopterus sphinx and Rousettus leschenaulti) that feed ex situ and a large-sized fruit bat (Pteropus giganteus) that feed in situ on a bat fruit (Madhuca indica). No fruit was removed on the ‘first’ attempt itself by both the bats; instead, they made multiple (two to six) repeated search attempts to the same bunch of fruits, which is presumably a behavioural mechanism underlying assessing the ripeness status to increase the chance of removal of ripe fruits. The emission of scent compounds was examined using a high-sensitivity headspace proton-transfer-reaction mass spectrometer in real time without any pre-treatment. As predicted, the fruits at the predispersal (unripe) and dispersal (ripe) phases differed significantly from each other in terms of concentration (intensity) of volatile compounds although no difference was inferred in terms of their composition. This study, thereby, highlights the underlying chemical basis of the foraging behaviour of fruit bats while foraging on bat fruits that finally effectuate its seed dispersal (chiropterochory).